RAPID PROTOTYPING - AN OPPORTUNITY FOR CHANGE

RAPID PROTOTYPING - AN
OPPORTUNITY FOR CHANGE?
By Simon Major,
Technology Centre, Thorn Lighting Group,
October 1993.
Summary:
This report investigates the opportunities available to the Thorn
Lighting Group by using 'Rapid Prototyping' technologies. It
considers the implementation issues and cost / benefit analysis.
The report indicates several paths forward.

Page ii
BRIEF CONTENTS
1. Introduction........................................................................................................................5
2. The Available Technologies ..............................................................................................9
3. Trials ..................................................................................................................................22
4. Approaches ........................................................................................................................28
5. The Future..........................................................................................................................38
6. Contacts..............................................................................................................................41
7. Recommendations..............................................................................................................47
8. Conclusions........................................................................................................................49
Index ......................................................................................................................................50

Page iii
DETAILED CONTENTS
1. Introduction........................................................................................................................5
1.1. Aim......................................................................................................................5
1.2. Objectives............................................................................................................5
1.3. What is Rapid Prototyping? ................................................................................5
1.3.1. The Subtractive Alternative..................................................................5
1.3.1.1. Opportunities within the Thorn Lighting Group ...................6
1.3.2. The Additive Processes ........................................................................7
1.4. Thorn Lighting's Current Approach ....................................................................7
2. The Available Technologies ..............................................................................................9
2.1. Model Production................................................................................................9
2.1.1. Model Preparation ................................................................................9
2.1.1.1. Orientation.............................................................................9
2.1.1.2. Subdivision............................................................................11
2.1.2. The STL File.........................................................................................11
2.1.2.1. Packing the Machine .............................................................12
2.1.2.2. STL Manipulation by the Specialist......................................12
2.2. The Processes......................................................................................................13
2.2.1. Photo Curing (Stereolithography) ........................................................13
2.2.1.1. Raster Scanning verses Masking...........................................13
2.2.1.2. Post Curing............................................................................14
2.2.2. Selective Laser Sintering (SLS) ...........................................................14
2.2.3. Laminated Object Manufacture (LOM)................................................15
2.2.4. Deposition ............................................................................................15
2.2.5. Selective Binding..................................................................................16
2.3. The Machines......................................................................................................16
2.4. Comparisons........................................................................................................19
2.5. The Bureaux........................................................................................................20
3. Trials ..................................................................................................................................22
3.1. The History of Mk 14 Pop Pack..........................................................................22
3.2. The Son Pak ........................................................................................................23
3.3. The Adagio Arm..................................................................................................23
3.4. The Jubilee Line Extension.................................................................................26
4. Approaches ........................................................................................................................28
4.1. Applications ........................................................................................................28
4.1.1. Freeform Styling and Geometry...........................................................28
4.1.1.1. Prosthetics .............................................................................28
4.1.2. Rapid Tooling.......................................................................................29
4.1.2.1. Currently Feasible Techniques ..............................................29
4.1.2.2. Processes Under Development..............................................29
4.2. Resources ............................................................................................................31
4.2.1. In-house................................................................................................31
4.2.2. External Bureaux..................................................................................32
4.2.3. The ‘Thorn Lighting Bureau’ ...............................................................32

Page iv
4.2.4. Collaborations ......................................................................................32
4.3. Philosophy...........................................................................................................32
4.3.1. Concurrent Engineering........................................................................33
4.3.1.1. Testing...................................................................................33
4.3.1.2. Production and Standards Engineering .................................34
4.3.1.3. Assembly...............................................................................35
4.3.1.4. Packaging ..............................................................................35
4.3.1.5. Marketing ..............................................................................35
4.3.2. Right First Time ...................................................................................35
4.3.2.1. The Son Pak...........................................................................36
4.3.2.2. Competitive Designs .............................................................36
5. The Future..........................................................................................................................38
5.1. The Interface........................................................................................................38
5.2. Processes .............................................................................................................38
5.3. Specialist Production...........................................................................................40
6. Contacts..............................................................................................................................41
7. Recommendations..............................................................................................................47
7.1. The Short Term ...................................................................................................47
7.2. The Long Term....................................................................................................47
8. Conclusions........................................................................................................................49
Index ......................................................................................................................................50
Figures........................................................................................................................50
Tables .........................................................................................................................50
Plates ..........................................................................................................................50
General Index .............................................................................................................51

1. INTRODUCTION
1.1. AIM
The aim of this report is to identify the opportunities open to the Thorn Lighting Group
regarding the use of ‘Rapid Prototyping’.
1.2. OBJECTIVES
• To identify all the Rapid Prototyping techniques and characterise their differences.
• To determine the opportunities that Rapid Prototyping presents.
• To carry out cost/benefit analysis on the techniques.
• To identify the pit falls of pursuing the different avenues.
1.3. WHAT IS RAPID PROTOTYPING?
‘Rapid Prototyping’ is the generic name given to a group of techniques for achieving a
common end. This end is to produce a physical representation from any visual one in a short
time. The qualifier of ‘in a short time’ is vague - the only consistent definition is: a small
fraction of the time taken to produce the required production tooling (or program) and then
manufacture the first part. The initial visual representation must be three dimensional in order
for the physical representation to be produced. The visual representation used is therefore a
three dimensional CAD model.
Rapid Prototyping techniques cannot produce a part at competitive long run production
prices. It can therefore only be used to produce one off items or prototypes - hence its name.
The approaches to forming a component can be classified as: additive, uniting1, casting2,
subtractive and reforming. This list is in descending order of flexibility of the geometry that
may be produced. Rapid Prototyping techniques generally use processes belonging to the first
classification. It will be demonstrated that the first three techniques have to be used in
conjunction to achieve the desired results.
1.3.1. The Subtractive Alternative
The alternatives to the specialist additive techniques are the more limited subtractive ones. In
practice this is the automatic programming of CNC machining centres direct from a CAD
model. This is a very useful capability if the company is in the business of producing
components by CNC machining - the Thorn Lighting Group is not. These techniques may be
used for more generic prototyping, but the geometry that can be produced is limited. Most
1 This process requires sub-components that are usually produced by other techniques.
2 This process requires a mould to be produced. The mould must be manufactured by other techniques.

machines in use are three axis ones; such a three axis boring or milling machine cannot
produce the following simple geometry without human intervention:
Figure 1 ‘Free Hand Sketch of a Non 3 Axis Geometry’.
It would be possible to make this shape automatically using a four axis machine. It is not
difficult define geometries that will defeat a five or six axis machine. At this level of
complexity the machines are extremely expensive.
There have been some successful applications of subtractive Rapid Prototyping techniques:
some motor manufactures, e.g. Renault uses 5 axis machines to rough out the shapes for their
body styling model makers; another application area is ‘bottle’ modelling. The model is solid
and produced in two halves. A common piece of CAD/CAM software used for this is
Delcam. It is necessary to form to halves of a mould and two halves of a core to make a
hollow bottle. In contrast the additive techniques can produce these geometries directly - the
new fluted Coca Kola bottle was prototyped this way.
1.3.1.1. Opportunities within the Thorn Lighting Group
There is a single three axis milling machine within the Thorn Lighting Group UK, and this is
at Hereford. The situation regarding the foreign operations is unknown. The investigation of
the use of Bridgeport Interac 4 machine has not resulted in any success. The situation has
been left with the manufacturer pursuing the software problems; but it is the author's opinion
that there is no future down this avenue.
1.3.2. The Additive Processes
All the Additive techniques used in Rapid Prototyping ‘grow’ a model in layers. The three
dimensional shape is divided into sheets that are stacked to form the model. This cycle is
depicted in the following exaggerated figure:

Figure 2 ‘Lamina Model Construction’.
The figure demonstrates that there is a vertical tolerance of a lamination thickness. This
distance is of the order of a tenth of a millimetre. This gives the impression that such a lamina
model is very coarse. The problem is mitigated by a significantly higher accuracy in the
horizontal plane; however surface finish is probably the largest weakness in the current
generation of technologies.
1.4. THORN LIGHTING'S CURRENT APPROACH
The company uses three general classes of components:
1. Fabricated sheet metalwork.
2. Plastic mouldings and metal castings
3. Extrusions
The sheet metalwork components do not need a special prototyping process as it is easy to
make these by hand; and it is not very difficult to program the flexible production machines;
also neither of these methods are expensive. The same cannot be said for the remaining

classes. There is therefore the potential for the application of Rapid Prototyping techniques.
Both of the remaining classes follow one of two routes3:
Direct development of production tooling - lower cost production tooling is produced
directly from the detail designs. These tools tend to be single impression in the case of
moulds. This approach has the danger that the design may not be perfect. The tool
then has to be reworked and the costs have risen significantly above the original
estimates.
Using soft tooling - a lower cost single impression tooling is used for pre-production work.
This tooling has a short term life span as it not made of hardened material. When the
design is finalised the production tooling is produced.
Either route is normally preceded by prototypes made in the model shop4. These models are
constructed from fabrications and machined pieces. These techniques work well for most
components. The exceptions are: if the geometry is too complex; or the component is too
small and fiddly. It should be noted that some capabilities are sub-contracted.
3 The author is not aware of any use of permanent casting moulds; therefore there is no equivalent to using soft
tooling in the case of castings.
4 This is extremely restricted in the case of extrusions.

2. THE AVAILABLE
TECHNOLOGIES
The production sequence that is common to all the processes shall be described before the
processes themselves. The following sections of the report will demonstrate that there is no
winner or ranking between the processes - different applications favour different processes.
All the processes have some common limitations.
2.1. MODEL PRODUCTION
All the specialised processes occupy the same role in the Rapid Prototyping cycle:
1. Three dimensional CAD design.
(2. Model preparation to decrease cost and improve quality).
3. File Generation.
(4. The option of file manipulation if stage 2 was bypassed).
5. The Rapid Prototyping building process.
6. Post processing.
(7. Model Reassembly).
(8. Replication Casting).
The stages 1 to 3 are completed by the in-house design function. The first four stages have a
profound impact on the cost and quality of final models; their influence is probably as
significant as the choice of process in stage 5. The issues regarding these early stages will
now be addressed.
2.1.1. Model Preparation
There are choices that can be made regarding the orientation and the possible subdivision of a
model. These decisions respectively affect the quality and cost of the model. Further cost
savings may be achieved by hollowing out parts of a model. The last point only applies to
certain processes.
2.1.1.1. Orientation
There are three issues regarding orientation:
1. Overhangs.

2. Curved detail.
3. Height.
Overhangs do not affect some processes at all. All the other processes can cope with small
overhangs; but the model will distort if large ones are present. There are two possible
remedies: the easiest, if it is possible, is to invert the model thus turning an overhang into a
base. If the large overhangs cannot be eliminated this way then supports have to be modelled
around it.
In section “1.3.2. The Additive Processes” the difference in horizontal and vertical accuracy
was described. The effects of this are most noticeable in the curved details of a model.
Consider the modelling of a cone: if this is oriented with its axis vertical then it constructed
from a stack of circular discs; however if oriented with its axis horizontal then it is
constructed from a stack of triangles. A second example is a plain hole: with its axis vertical
it is perfect; whereas if it is horizontal it has a stepped circumference.
In section “2.1.2.1. Packing the Machine” the importance of filling the modelling volume is
discussed. The volume that needs to be filled is not the maximum capacity of the machine -
the depth need only be slightly greater than the height of largest model. It is therefore
desirable to orient a model to minimise this height. The situation is not as simple as orienting
all the components for minimal height if the process requires model supports. This is
demonstrated in the following figure:
Figure 3 ‘Stacking in a Rapid Prototyping Machine’.
Vertical stacking of models that are not self supporting is not very practical. The figure
demonstrates that complex supports with complete bases may be needed. If vertical stacking
is not used it can be seen that orienting all the components for minimum height is not the best

approach for the example shown in the figure. It is generally the case that processes that do
not need support can achieve much greater packing densities. These processes also allow the
rule of minimum height orientation to be used all the time.
2.1.1.2. Subdivision
There are three reasons for subdividing a model:
1. Size.
2. Packing efficiency.
3. Variable geometry complexity.
4. Height reduction.
The size of component that may be produced in one piece by Rapid Prototyping is limited.
The size ranges from ‘small’ machines with a base in the order of 10" square; to the largest
machines with a base approximately 20" square. Larger components can therefore limit the
choice of machine.
The parts modelled using Rapid Prototyping have complex geometries - simple geometries
can be made by other means. These complex geometries contain a large volume of empty
space within the envelope of their overall dimensions; consequently they do not pack very
efficiently into the volume of the machine. It the part's envelope volume that most commonly
determines the cost of the model. It is therefore desirable to subdivide the model into several
component parts that are more volume efficient.
A model may consist of a section of complex geometry joined to a bulky piece of simple
geometry. Rapid Prototyping only the complex section may save money in such
circumstances. The rest of the part is produced by other means and then the two are reunited.
The need to reduce the height of the model in the machine was discussed in section “2.1.1.1.
Orientation”. If the highest point of a part is the tip of a significant protrusion; this can be
sliced off and modelled separately.
2.1.2. The STL File
Rapid Prototyping requires a transfer of geometric information between a CAD machine and
the building machine. There are a large number of incompatible CAD information formats -
an interchange format is required. The de facto standard is the STL file format that was
developed by the original supplier - 3D Systems.
The cost reducing measures described in the in the preceding sections can either by applied to
the CAD representation or the STL representation. The former requires that the originator has
some prototyping expertise; whereas the latter can be dealt with by the Rapid Prototyping
specialist. The latter option would seem preferable as some of the activities refer directly to
the machine.

2.1.2.1. Packing the Machine
Only some of the building processes can recover the material not used in the manufacture of a
model. If a process cannot recover the waste then this waste must be minimised; therefore the
volume of the machine must be packed with models as tightly as possible.
It is also beneficial to pack a machine that uses a process that can recover waste. The
production time for a machine building 30 parts is considerably shorter than the than 30 times
the production time of the same machine producing a single part. The production time is an
important consideration because the cycle times are extremely long - typically 3 to 30 hours!
2.1.2.2. STL Manipulation by the Specialist
The model originator would produce a STL version of the basic model and pass this to the
specialist; they would then carry out all the manipulation to produce the cheapest, highest
quality models. The only problem with this scenario is the STL file format itself. The format
was made compatible with all the CAD systems by making it a universal simplification. The
STL version is a faceted approximation rather than a true representation of a geometry - all
the surfaces of the model become meshing triangles. Any manipulation of STL file will not
completely correlate to the true model. If the same manipulation is carried out on the CAD
model and to a STL file it is then possible to convert the new CAD model to a STL version
for comparison. It is not likely that the two STL files exactly match! The differences will be
small and so the errors are normally insignificant; however it will be shown that a Rapid
Prototyping model is prone to accumulate errors.
The facetting may either be fine or coarse. If the facets are similar in size to the lamina
thickness then there is no degradation of the final model. Very large facets will be visible in
final model. This facetting introduces a normally insignificant amount of dimensional error. It
also spoils the appearance of an already poor surface finish. The irony is that the problem is
not with areas of high geometric complexity; instead it is with the simple features such as a
cylindrical wall! The standard practice is to smooth the surface by removing material. This
also introduces dimensional error.
These errors make Rapid Prototyping unsuitable for modelling extremely precise functional
features such as interference and tolerance fits. This is not a problem for the Thorn Lighting
Group as the components that would prototyped are not of such high precision.
One problem Thorn Lighting does not have is with the CAD models. The company uses a
solid modelling CAD environment - which is the best possible type for STL file generation.
Other systems can produce problems that require the STL file to be ‘fixed’ by the specialist.
The company also has the software to convert its CAD files to STL files. What it would not
have is any control over the process. This is because the company has no STL viewing or
manipulation capabilities.
Viewing facilities can be implemented by converting the STL format generated back into a
CAD file. This file is not the same as the original geometry; instead it is a CAD model of
faceted object that is similar to the original. Any problems, such as large facets, would then
be visible in the CAD system. The best facilities available allow the coarseness of the STL
conversion to be adjusted; they even allow this to be set differently for different parts of the

model. Thorn Lighting is unlikely to get any of these facilities from Hewlett Packard as our
STL generator was supplied free and without any support.
Is there any alternative to STL? There are a couple of competing proprietary file formats that
have not taken off. There is a need for a new format. The development in this area is
discussed in section “5.1. The Interface”.
2.2. THE PROCESSES
2.2.1. Photo Curing (Stereolithography)
There are a number of different suppliers that use variants of this process; while the other
processes are only used by single suppliers. This is the original, and hence the most
competitive, form of Rapid Prototyping. The majority of people only know this process if
they are even aware of Rapid Prototyping. This process was used in over 93% of the world's
machines in early 1992, but this figure is falling.
The layers of the model are produced by the selective curing of photosensitive polymer resins.
There is a wide variation on how this is achieved. Most of these systems require supports for
large overhangs; but all of them recover waste. The systems that do not require supports have
a more complex layer building cycle: after a new layer is cured the uncured resin is removed
and replaced by a support material, e.g. wax. The quality of models produced using these
techniques are dependent upon both the physical methods used and the qualities of the photo-
polymer. It is very easy to overlook the effects of the latter.
The most ignored part of the Rapid Prototyping cycle is the cleaning stage - the removal of
unused material from the model. In the systems that are not self-supporting the model comes
out of the machine covered in uncured resin. This is thick and sticky. It must be removed with
the use of unfriendly solvents. The support material used in self supporting systems is
intended to be easily removed; however it should be remembered that the mixed material
from such a process has to be removed from the machine as one large solid block!
2.2.1.1. Raster Scanning verses Masking
There are two possible approaches to selective curing: raster scanning and masking. In the
former the area to be cured is raster scanned by a laser. The masking technique is more
complicated: a mask of the area is prepared photographically or by electrostatics. The mask is
then used to shield the layer that is bathed in light. After the layer has cured onto the model
the mask is cleared and the cycle repeats.
The two techniques have different implications for material properties of the model. Different
manufactures will argue over which method is superior. The author is inclined to think that
the masking systems result in higher quality models; but these systems are more expensive.
The two techniques have different weakness: raster scanning causes stresses within each layer
that are dependent upon the scanning patterns; masking avoids such stresses but according to
raster manufacturers it can suffer from weak inter layer bonding. The result of is that the less

sophisticated resins tend to produce models that are brittle. No photo-polymer resins have
particularly good machining properties.
Raster Scanning manufactures compete with each other on the grounds of the fine detail of
their scanning techniques. This can be deceiving as the final quality is highly dependent on
the resins used.
2.2.1.2. Post Curing
If the layers are cured by raster scanning then there are two options: the area may be cured
completely by the laser, or it can be partially cured by the laser and the completed model is
then cured later. This post curing is achieved by bathing the model in light whilst it rotates on
a table. The difference between the two processes is that the partial curing allows the layers to
be built more quickly. The problem with post curing is that it causes shrinkage and distortion.
This tendency is highly dependent on the quality of the resins.
If the geometries are highly curved and thick walled then the model is self reinforcing. In this
case there is no distortion. Distortion is most likely to occur in thin walled, large area, flat
surfaces.
2.2.2. Selective Laser Sintering (SLS)
The layers are produced by selective local sintering of powdered material. The localised
sintering is achieved by raster scanning with a laser. Presently the process is used without any
post sintering. The unsintered material is recovered after the completion of the model. Before
this the unused material fully supports the growing model. The process has another advantage
- the material does not have to be specialised, and can therefore be changed among production
materials. The ease and speed of a material change are issues. Any implementation that would
require frequent material changes is not likely to be successful: apart from the change over
time it increases work in progress and the throughput time. This can be explained
hypothetically: if it takes 10 parts to economically fill the machine then the work in progress
is at least 10 parts, i.e. you must wait for a ten part backlog to accumulate before you can run
the machine. The work in progress and the throughput time are doubled if the machine is used
equally for parts in two different materials. The process therefore becomes half as ‘rapid’.
The process is not perfect - it achieves a sintered density equivalent to that of only a low
quality production sinter process. On the positive side the process does not suffer any
shrinkage or distortion, and the model is in a production material.
The cleaning process for selective laser sintering is easy and environmentally friendly. The
non hazardous powder is blown from the model using compressed air.
2.2.3. Laminated Object Manufacture (LOM)
This is a very simple system with that has unique advantages and disadvantages. The material
is neither a fluid or a powder; instead it is a roll of specialised sheet material. The sheet is a

bulk material that has a thermally setting adhesive on the back. The bulk material can be
metal or plastic, but it is usually paper!
The roll is wound across the top of the stack of model and support material. A new layer is
added by winding on a length of roll; then cutting out the profile of the layer with a laser;
finally the layer is completed by passing a heated roller over the length of the stack. This
binds the layer to the one below using the adhesive.
The advantages of the process are: that the machine is cheap to purchase and run; the model is
self supporting and suffers no shrinkage or distortion; and a paper/adhesive laminate comes
out with material properties and appearance of wood. Wood is very easy to rework. This is an
impressive list; unfortunately the it has a huge disadvantage at the cleaning up stage. The
model comes out of the machine in a fused block with the support material and has to hacked
out. For the same reason the process is hopeless for enclosed volumes because it becomes
impossible to dig out the waste material.
2.2.4. Deposition
There is one established deposition technology, though there are several particle deposition
technologies in development. These are discussed in the section “5.2. Processes”. The
established technology extrudes a fine stream of thermoplastic paste. An unflattering analogy
is to imagine modelling with tube of toothpaste. This process can be adjusted between, slow
but high quality, or fast and coarse. There is no waste and a single part may be produced just
as economically as many. This allows the work in progress to be low which makes this the
most rapid Rapid Prototyping for low volume users. The process can use a variety of
materials that can be changed over easily.
The principle limitation of the system is that there is no support material and it is very poor at
unsupported geometry. This problem could be cured by having a second tool extruding
support material. The system would then be extremely effective. The system is clean enough
to be office based and there is no clean up stage required.
2.2.5. Selective Binding
Selective binding is presently a more specialised technique. It is used the rapidly produce
ceramic shell castings. The approach is most closely related to selective laser sintering. The
material in this case is a ceramic powder; and instead of local sinter there is local spraying of
a binding agent using inkjet technologies. The model is fired after completion. This process is
of little interest to the Thorn Lighting Group.
2.3. THE MACHINES
This section contains a brief summary of the details of every Rapid Prototyping system that
the author has been able to find. The descriptions refer to the definitions in section “2.2. The
Processes”. The manufacturers are listed in order of market share; or if their market share is
unknown then they are placed towards the end of the list.

Manufacturer Product Details
3D Systems SLA-500 The original Rapid Prototyping manufacturer.
The machines use a UV raster scanned photo-
curing process with post curing. The process is
not self supporting.
They have been developing their resins
continually; these are supplied by Ciba-Geigy.
Model size: 20"×20"×24"
Capital: $420000 @ Dec. '92
SLA-250 Model size: 10"×10"×10"
Capital: $210000 @ Dec. '92
SLA-190 Model size: 7.5"×7.5"×9.8"
Capital: $95000 @ Dec. '92
Stratasys three
dimensional
Modeller
Deposition system that can change among 3
materials: a nylon like thermoplastic; a
machineable wax; and an investment casting
wax. Its biggest benefit is that its model costs
do not soar at low levels of utilisation. The
process cannot cope with significant
overhangs.
Model size: 9"×12"×13"
Capital: $178000 @ April '91
Cubital Solider 5600 This is the Rolls Royce of the Rapid
Prototyping world. The process is photo-curing
but it is self supporting UV masked and there
is no post curing. The models produced have
one of the best surface finishes; they are very
strong for a photo-polymer; and the models do
not shrink or warp. The Solider is designed for
very high throughput of models with many
models packed into a single production cycle.
The machine is huge and permanently manned;
if not used at capacity it is extremely
expensive. It has good facilities: layers can be
erased if something goes wrong; if a model is
split the software will automatically hole and
dowel the mating surfaces to assist in
reassembly. The post processing consists of
dissolving off the support wax in a mild acid
bath.
Model size: 20"×20"×14"
Capital: $550000+ @ Dec. '92

DTM Sinterstation
2000
The process is selective laser sintering. The
materials currently available are nylon,
polycarbonate and an investment casting wax.
Model size: 15"×12"∅
Capital: $95000 @ Dec. '92
Helisys LOM 1015 The process is laminated object manufacture.
The rolls available are paper, polyester and
metallic. A feature of this machine is its
compactness.
Model size: 14.5"×10"×14"
Capital: $95000 @ Dec. '92
LOM 2030 This is a new larger model.
Model size: ? 20+" (World's largest)
Capital: $180000 @ Dec. '92
Soligen Inc. DSPC The process is selective binding using ceramic
powders and colloidal oxide binders to
produce ceramic shell castings. The
technology is based upon that developed by
MIT.
Model size: 12"?×12"?×24"?
Capital: $200 - 250000? @ Dec. '92
Light Sculpting
Inc.
LSI-0609 An alternative photo-curing process that uses
masked UV.
Model size: 6"×6"×9"
Capital: $99000 @ Dec. '92
LSI ? Newer model(s). These may use very fast LCD
masking technologies.
Model size: ?
Capital: $159000 @ Dec. '92
SOMOS
(EOS)
(Teijin Seiki)
The chemical giant du Pont developed a photo-
polymer resin in conjunction with the SOMOS
system. High hopes were expected of this but
they delayed before licensing the technology
out. They felt that the market was developed
enough. The licensed technology is quite
‘new’ and therefore an unknown. The
processes fully cures the resin by raster
scanning; however the model is later heated to
toughen it.
Model size: 12"×12"×12"
Capital: ?

Table 1 ‘Currently Available Rapid Prototyping Machines’.
2.4. COMPARISONS
The reader is by now aware of the complexity of the issues affecting the selection and
performance of a Rapid Prototyping system. The most comprehensive comparison carried out
was by the Chrysler Motor Corporation. It is possible to choose models and throughput rates
that will cause any of the listed systems to win. In Chrysler's case the deck was favoured
Cubital's Solider. If the Solider is ignored the table can be used to make some reserved
comparisons.
Quadrax Laser
Technologies Inc.
Mk 1000
LMS
This US firm uses a photo-curing process. The
layers are fully cured with a very high power
visible light sophisticated Raster Scanning
laser. In most Rapid Prototyping systems the
model lowers into the vat, etc. as new layers
are added. In this system the model remains
stationary and the optics rise.
Model size: 12"×12"×12"
Capital: $195000 @ April '91
Sony SCS The Sony and the Mitsubishi products are not
known about except for the fact that they are
both photo-curing processes.
Mitsubishi ? see above
CMET SOUP This is an unknown Japanese photo-curing
system. There is the possibility that this could
be the Sony or Mitsubishi products mentioned
above.
DMEC Solid
Creation
System
See above (this probably the Sony system
SCS).

3D
Systems
3D
Systems
Cubital
Solider
5600
DTM 2000 Stratasys
3D
Modeller
Helisys
LOM
1015
Cost of Equipment (#) $210 000 $420 000 $490 000 $397 000 $182 000 $85 000
Depreciation Cost / hr
(5 yr. 85%)
$5.24 $10.61 $13.16 $10.66 $4.89 $2.55
Service Contract / yr. $36 000 $85 000 $49 000 $68 000 $7 000 $17 000
Pre-processing Time
(hr:min)
00:34 00:34 00:21 00:35 04:20 00:46
Build Time (hr:min) 05:06 04:44 09:26 03:00 08:00 09:51
Post-processing Time
(hr:min)
01:45 01:45 01:00 01:19 00:15 00:25
Total Process Time
(hr:min)
07:25 07:03 10:47 04:54 12:35 11:02
Maintenance Cost /
part
$24.66 $54.03 $1.88 $27.40 $7.52 $22.49
Pre-processing Cost $38.02 $38.02 $23.35 $38.69 $288.82 $51.36
Build Cost less
Attendant
$28.77 $53.40 $3.76 $31.99 $39.11 $22.49
Post-processing Cost $38.50 $38.50 $22.00 $29.27 $5.50 $9.24
Total Material Cost $4.00 $4.00 $31.43 $5.89 $4.00 $3.82
Cost of Attended
Operation
$0.00 $0.00 $6.29 $66.00 $0.00 $0.00
Total Part Cost $133.95 $187.95 $88.71 $199.24 $344.95 $109.40
# Prices 10/06/92 33 parts
together
Table 2 ‘Chrysler's Rapid Prototyping Benchmark’.
The most useful pieces of information are the timings and the maintenance and depreciation
costs that probably convert at the rate of $1 equals £1. It is immediately apparent that an
internal facility has very high overheads.
2.5. THE BUREAUX
The Rapid Prototyping market is very young; with a low number of machines in the country.
There are some machines used in internal facilities; but these subsidise themselves by also
acting as bureaux. The known UK bureaux are listed in the following table in the author's
order of preference:

Table 3 ‘UK Rapid Prototyping Bureaux’.
Bureau Machine(s) Details
Formation
Engineering
Services
3D Systems'
SLA 250
This firm offers very good service at a
competitive price. They offer the best value for
money pricing structure: it is related to the
model volume rather than the overall dimension
envelope.
They come recommended by Hewlett Packard.
Rover Group 3D Systems
(all sizes)
The most extensive user of Rapid Prototyping
with 4 SLA machines running continuously.
They quote from experience rather than a
formula.
Sherbrook
Automotive
(Cubital's
Solider)
They carry out the preparatory work and then
sub-contract the Solider time from Schneider in
Germany. If there is any re-assembly or
replication casting to be done then this is carried
out by Sherbrook. They quote by envelope
volume - at '93 prices per cubic centimetre:
0 - 500 £350
501 - 1000 £575
1001 - 3000 £850
3001 - 5000 £1675
5001 - 10000 £2775
10001 - 20000 £4150
20001 + £ P.O.A.
Umak Helisys'
LOM 1015
They charge £100 + £50 / hour exclusive of
VAT.
In the past models requiring the LOM 2030 have
been produced at Helisys' facility in Los
Angeles.
RP&T
Consortium
(Warwick
University)
Helisys'
LOM 2030
RP&T is a collaboration with Rover Group.
They have only just started.
Rolls Royce 3D Systems ? Rolls Royce has purchased the technology and
they have a desire to sell machine time. No
details or contacts are known.

3. TRIALS
Rapid Prototyping is a very impressive facility; but is it economically viable or even useful to
the Thorn Lighting Group? The only way to answer these questions is to have a look at some
costs and quotations.
3.1. THE HISTORY OF MK 14 POP PACK
A line of investigation was to consider the impact that Rapid Prototyping could have had on
one of our most important products. There are two types of mouldings used in Pop Pack: the
spine end caps, and the diffuser end caps. The development of the spine end caps shall now
be considered. There are two of these: the single and the twin lamp holder versions. They
were developed using single impression soft tooling. The history of this development is
summarised in the following table:
Table 4 ‘Popular Pack Spine End Cap History’.
Quotations have not been sought for these components; but estimates can be made based
upon the Adagio arm. The later would cost £845 for the polymer model; therefore the two
Pop Pack components should cost no more than £1200; they could cost less than £845! The
original design had to be modified after visual appraisal and test assembly using the
prototype. It shall be assumed that the original Rapid Prototyping model would also be
incorrect, an that it cannot be modified. A new Rapid Prototype model is therefore produced -
another £1200. The rework caused a delay in the completion of the component of over three
months. The changes made are only minor; therefore the Rapid Prototyping approach would
cause a delay of under a month. If the change to production tooling was made at this point
there would have been a saving of at least £880 pounds. The contribution from eliminating
two months of delay is impossible to calculate.
The most likely Rapid Prototyping approach would probably be more cautious - correct
material replicas would be produced for thermal and strength testing. The Adagio estimate
would indicate something like £1600 pounds for a short run of replication mouldings. This
more cautious approach would make the Rapid Prototyping approach more expensive than
the one; but this would be offset by all the time savings.
Requirement Date PR
Number
Price
Single Impression Soft Tooling 11/01/92 117298 £2500.00
Modification to the Soft
Tooling
13/04/92 119834 £780.00
250 Single and 250 Twin
Mouldings from the soft
tooling
04/06/92 122669 £252.50

3.2. THE SON PAK
The new Son Pak was to have a one piece polycarbonate moulding for its body. Quotations
were therefore sought for Rapid Prototyping both this and the front cover. The quotations
were obtained from several bureau services:
Table 5 ‘Ian Thorniwell's Son Pak Quotations’.
The models are quoted for without any cost saving preparation, i.e. subdivision. The body of
the Son Pak is not very volume efficient; it is also quite large. It is a shame that the Formation
quote is for producing the model from drawings rather than a STL file because then the cost
would be lower. The biggest surprise is the poor competitiveness of the LOM model. This is
probably due to the large model height of the Son Pak body.
3.3. THE ADAGIO ARM
Half of the Adagio arm was used as a STL file transfer test. This component had been
‘rapidly prototyped’ without using the specialist technology; it was therefore decided to seek
quotations for comparison. The medium level of complexity in the component is visible in the
following plate:
Bureau Quotation for Son Pak
Formation (SLA) £2192
2 weeks from two dimensional
drawings
Umak (LOM) £2632
£686
= £3318
1 week (+£520 from two
dimensional drawing)
DTM £1600
(6 off £7200)
This is not a normal bureau
quotation - the quotation is from
the manufacturer. The price is
low because this would be an
experimental collaboration.
from STL
Sherbrook (Solider) £3910
£785
=£4695
2 weeks from STL

Plate 1 ‘The Adagio Arm (half)’.
Two quotations were sought to compare the prices of two bureaux offering an identical
service. These are then compared with the more conventional approach used. This
information is represented in the following three tables.
Table 6 ‘Rover Group's Quotation for the Adagio Arm’.
Service Supplier Cost
Stereolithographic Master.
1 off of single half.
Rover Group Ltd. £1112
Vacuum Casting Mould
1 off (produces single half)
Rover's internal facility is overworked, ∴
sub-contracted to ?
?
10 off Urethane resin
vacuum castings
as above ?

Table 7 ‘Formation Engineering's Quotation for the Adagio Arm’.
Table 8 ‘Cost of the Two Halves of the Adagio Arm without Using Rapid Prototyping’.
Why does Rapid Prototyping compare badly? The tapers that make the geometry complicated
were ignored in the CNC model. This was acceptable for this application. The geometry could
therefore be produced fairly cheaply using CNC techniques. Their price was nevertheless
surprisingly low and their methods should therefore be investigated if possible. It may be that
Stereolithographic Master.
1 off of single half.
Formation Engineering Services Ltd. £845
(delivery 1
week)
1 off (produces single half)
Formation Engineering Services Ltd. £690
vacuum castings
as above 10 × £72
= £720
CNC approximate Master.
1 off of each half.
Aycliff Tool & Gauge,
Unit 3, All Saints Industrial Estate,
Shildon,
County Durham. DL4 2JU
(0388)776298 (fax)
£350
(delivery not
known
PR126955)
1 off (produces both halves)
A.T.O.M. (Industrial Model Makers) Ltd.
Hope Works,
High Street,
Sunningdale,
Ascot,
Berkshire. SL5 0NG
(0344)20001
(0344)28028 (fax)
£375
(completion
1 week)
vacuum castings
as above 10 × £50
+ £100
= £600
(delivery 1
week)

they are using the automatic profiling technology described in section “1.3.1. The Subtractive
Alternative”. The quotations reinforce the notion that Rapid Prototyping is best suited to
components of very high complexity.
Replication casting is an important optional part of the Rapid Prototyping cycle. The
quotations supply evidence that this aspect of the service offered by the bureau services is not
the most competitive. Rover's in-house replication facility is over worked; they therefore have
a list of replication casting sub-contractors. These are likely to be more competitive. If Thorn
Lighting becomes involved in Rapid Prototyping it should compile its own list that is as
exhaustive as possible.
3.4. THE JUBILEE LINE EXTENSION
Cost savings at the pre-production stage are not the only reasons to carry out Rapid
Prototyping: bid support is another. The largest potential project in Thorn Lighting at the time
of writing is the London Underground Jubilee Line Extension. The platform fitting has
already been concept designed by London Underground. Thorn Lighting is bidding to prove
and manufacture the fitting. To do this prototypes are required. This is a project with enough
financial impetus to act as a pilot project for the use of Rapid Prototyping.
The question remains whether the technique is suitable for the components of this fitting. The
fitting consists of an extrusion and two end caps of similar cross-section. The extrusion is too
long to fit in any machine in one piece. It is also unlikely that it will be cost effective to
model this even if the component is manufactured in identical replicated sections. This has
been quoted for anyway in case there is a lead-time problem with the competing soft tooled
extrusion approach.
The cross sections of all the parts restrict the quotations to the largest Rapid Prototyping
machines available. It would be a good idea to obtain a quotation for the end caps
manufacture on a LOM 2030 machine - this may be more competitive for these geometries.
The deciding factor whether not the end caps are suitable for Rapid Prototyping is their
geometric complexity - the situation may be the same as the Adagio arm.
The quotations following are based upon the partial details available when the company first
received the London Underground assembly drawings:

Table 9 ‘Quotations for Jubilee Line Extension Platform Fittings’.
Supplier Part Details Cost
Rover Extrusion
(3 off)
SLA Polymer only quote £11224
2 End Caps
(3 sets)
SLA Polymer only quote £2518
Sherbrook
Automotive
Extrusion
(for 3 off)
Solider Polymer only - 1 off master for
duplication casting (306 mm length sections)
Duplication aluminium casting and reunion
Completion of polymer master: 2 weeks
Duplication casting: +3 weeks
These quotations are provisional as only
partial details were supplied.
£3900
£ ?
2 End Caps
(for 3 sets)
1 off each end polymer master
Duplication aluminium casting (insufficient
detail)
All prices exclusive of VAT and courier
charges @ cost from Germany.
£3140
?

4. APPROACHES
In this section of the report the applications, implementation and the philosophy behind Rapid
Prototyping are considered.
4.1. APPLICATIONS
Rapid Prototyping has so far been described as an alternative tool for use with current
practices. The technique permits changes in practice that are elaborated upon in section
“4.3.1. Concurrent Engineering”. There are also some unique capabilities that it offers.
4.1.1. Freeform Styling and Geometry
Rapid Prototyping excels with complex geometries. This fact can be extrapolated to: ‘Rapid
Prototyping facilitates the production of geometries that would otherwise be too expensive to
develop’. The company's products' geometries consist of straight lines, circles and slightly
rounded corners. The designs look ‘modern’, but the geometries are analogous to motor cars
of early eighties. Cars of the nineties are taking on freeform geometries that give them a
sophisticated futuristic look. A good example of this is the Mazda car company: their most
extreme example being the Xedos 6 - it probably does not contain a single straight line or flat
surface on the exterior! Such influences will ultimately filter through to the lighting industry.
There are two possible approaches to prototyping freeform geometries: clay craftsmen or
Rapid Prototyping techniques. The increase in the use of freeform geometries will probably
be the biggest medium term driving force behind Rapid Prototyping. The trickle down is
following the path of fashion conscious products. It probably started in the late eighties with
the personal consumer electronics industry5. In an environment of highly competitive markets
and rapid technological advancement, if one does not have a large technical edge over the
competition then it is important to have an aesthetic one. There are parallels in the lighting
market: the preference for low glare recessed fittings for general purpose areas. The choice is
aesthetic rather than functional.
4.1.1.1. Prosthetics
The freeform capabilities of Rapid Prototyping have been applied to the unique geometry that
is an individual's body. The geometry is ‘scanned’ into the system using either three
dimensional digitising; CAT scans or NMR scanners. This has already been used for artificial
limb mounts and replacing a severed ear with a silicone replica of the remaining one6! A
suggested application is to use models to practise experimental brain surgery. These
fascinating applications are of no interest to the Thorn Lighting Group.
5 The glassware industry has always used free form geometries because of the nature of the material. The zenith
of this styling is probably the perfumery industry.
6 Naturally the geometry was produced in mirror image.

4.1.2. Rapid Tooling
Rapid Prototyping has been described as a solution seeking the problem. There are pressures
that will inevitably lead to the ‘revolution’, but they are not sufficiently developed yet. The
advocates of Rapid Prototyping have therefore been looking for additional applications that
will lead to market growth. The application that is mainstay of current research is Rapid
Tooling. At the moment this application is nothing more that experimental; however if this
delivers on its promises then it will have as large an impact on manufacturing as CNC
machining and robotics combined! The technology promises to produce production tooling in
the same time as Rapid Prototyping. The impact of this can be emphasised by an example: a
brief is supplied for a simple moulded component; the design on CAD would only take a day
or so because of its simplicity. The tooling would be rapidly produced and production would
begin in under a week! The benefits of reduced time to market are extolled in section “4.3.1.
Concurrent Engineering”.
There are many avenues of Rapid Tooling that are under investigation. The main problem
with the technology at the moment is the surface finish. The surface finish on current Rapid
Prototyping models is not wholly acceptable. Current Rapid Tooling has an identical surface
finish. The surface finish on tooling determines the surface finish on the production
component; and a product surface finish equivalent to that of current Rapid Prototyping
therefore falls far short of the mark. In time the technology will become available. There is
presently no need for the technology; but the combined influences of competition and
consumerism will create the need as soon as technology is available.
4.1.2.1. Currently Feasible Techniques
The current surface finishes are suitable for some sand casting techniques. The reusable
patterns and core moulds are produced by Rapid Tooling techniques. The benefit is are the
very short lead times compared to the production of wooden patterns by craftsmen. The
danger is that components made by sand casting tend to be large. This would make the Rapid
Tooling model expensive. This can be alleviated by producing a hollowed tool that can be
filled with a cheap packing material. This technique has been successfully used in the
automotive industry.
Several processes offer one off investment casting modelling materials. This is presently not
suitable for one off production processes - only for producing one off metal prototypes.
4.1.2.2. Processes Under Development
Some of the techniques described below are a long way off. To be effective Rapid Tooling
techniques need to improve their surface finish by at least one order of magnitude. This will
take some time; but this problem is not fundamental and so success will ultimately be
inevitable. It is presently not possible to say how long this process will take; a wild guess
would be 5 to 10 years to fully mature.

Sintering dies - Rapid Tooling polymer dies have been used to press powder components for
sintering. The bound component is removed from the die and sintered in an oven. The
use of plastic as a tool material limits the die pressure. In turn the low pressure limits
the materials that can be pressed in preparation for sintering. The best results have
been achieved with pure copper. Unfortunately there is not much demand for pure
copper components; however it is ideal for single or multiple EDM electrode
production.
One of investment casting - Rapid Tooling models can be made directly in investment
casting material. These can be used for a single investment cast component. This
would be a very expensive method to use for production; however it could be used as
an intermediate process, e.g. to investment cast an injection moulding die. This
technique is of interest to the Thorn Lighting Group. Such an application would
require extremely high surface finishes - higher than that acceptable on a finished
product. This is a very big hurdle.
One off ceramic core and shell production - this is almost identical to the last process
regarding application. The direct production of ceramic shells is the same as
investment casting with one of the stages already completed.
The same technique can directly produce ceramic cores for use in another casting
process. This application would be extremely rare.
Investment casting mould production - Rapid Tooling could be used to produce mould for
a run of investment casting wax positives.
Laminated punch and die tooling - a metal film LOM structure is not particularly strong in
most respects. Its compressive strength perpendicular to the laminations is its
strongest line of action. If loadings can be restricted to this direction then it can be
used for limited tooling applications. The research carried out to date has used the
material as a low pressure sheet material profile punch. The low pressure caveat limits
the application to thin sheets of material that are not too tough. The tooling would be
better at forming actions than punching and shearing actions.
Such tooling would not be capable of punching fiddly features such as small diameter
holes. This problem could be dealt with by using tool steel dowels for these punch
parts. The dowels would be mounted in the full depth of the laminated tooling. Shear
actions would result in a very high rate of tool wear that would limit the tooling to
very short production runs. This would not be the case for a purely compressive
forming application.
Such tooling may be useful for other compressive die applications. For example, it
may make a better die than a polymer in the ‘Sintering dies’ application described
earlier. The sheet metal applications are of interest to the Thorn Lighting Group;
especially regarding short run products.

EDM electrode manufacture - a problem with Rapid Tooling techniques is that they cannot
directly produce tools of the toughest materials. Electrode Discharge Machining7 is
suitable for producing the most complicated geometries in such materials using
custom tooling. The electrodes are negatives of the surface to be produced and they
therefore have complex geometries. Such electrodes can be produced using Rapid
Tooling techniques. This may be the ‘Sintering dies’ process or any one off
production process.
EDM can only achieve a low material removal rate and is therefore best suited to
finishing operations. The most rapid Rapid Tooling would therefore be produced by
another method with a lower surface finish. This would then be finished using EDM
with electrodes produced by Rapid Tooling Techniques. In the long term Rapid
Tooling may reduce product life cycles to the extent that very hard tooling is no longer
required.
Direct metal component production - an expensive production process in which metallic
components are produced directly by a Rapid Prototyping process. This could possibly
be the cheapest technique for one off production of metal components with complex
geometries. There are questions over the material properties of such a component.
This is not necessarily a limitation - the properties could end up being superior!
There have been some exotic applications suggested for this: it is the most flexible
technique for the applications described in section “5.3. Specialist Production”; it can
also be used for field repairs to reduce spares stocks. The suggested needs for this are:
on an aircraft carrier and in a space station! Alternative Rapid Tooling techniques
could be used for these applications but they would require secondary processes.
Direct metal tooling production - this is the same process as the preceding one except that it
is used to produce tooling rather than one off components. This approach has much
wider applications and is of interest to the Thorn Lighting Group.
4.2. RESOURCES
There are a number of implementation approaches available.
4.2.1. In-house
The current technologies require large capital expenditure and they result in high overheads.
This approach is valid only if the company produces a high number of models. The internal
facility would give a company control over the process, especially regarding quality. Models
produced internally are several times cheaper than those made externally if the machine can
be fully utilised.
7 This is also the case for ECM (Electrochemical Machining). This process achieves a higher surface finish than
EDM but is less flexible regarding geometry.

Most processes have a work in progress problem that is exacerbated if the facility is in-house.
This problem is described in section “2.1.2.1. Packing the Machine”. It is this problem that
drives up the cost of parts made externally.
4.2.2. External Bureaux
This is the obvious approach for a low volume user. The different Rapid Prototyping
technologies have different specialisms; it can therefore be worthwhile for a higher volume
user to continue to use bureaux so that they may switch technologies from project to project.
A high volume user should also extensively ‘test drive’ the technologies before purchasing
for an in-house facility.
4.2.3. The ‘Thorn Lighting Bureau’
This is an extension of the in-house facility. This is commonly factored into the cost
justification for in-house plant. The external work helps to raise the utilisation as well as
supplying revenue. To use this in justifying the expenditure would be dangerous for the Thorn
Lighting Group because of several reasons: everybody else tries to do it; we do not have sub-
contract experience; and we have no expertise. The only successful implementation is the
Rover Group. It works precisely because they do not need to do it. Their corporate identity is
also a help. Following their example: external work should be the icing on the cake and not
part of the base.
The only significant hole in the UK bureau market is for the DTM Sinterstation 2000
machine. As a bureau machine it offers the largest opportunity to be ‘hyped up’ to attract
potential customers.
4.2.4. Collaborations
There are several collaborations that could be investigated. Some of these are research based;
while others are ‘clubs’ with members' rates; and others still will be bureaux by another
name.
There are a couple of these that may be of interest to the Thorn Lighting Group: the RP&T
Consortium looks interesting; and there is a joint project between the CAD/CAM Centre and
the Centre for Industrial Design. It is their intention to provide a Rapid Prototyping facility in
the North East but they have only just started. The Thorn Lighting Group has the opportunity
to be a user or a supplier of this project.
4.3. PHILOSOPHY
For ninety-nine geometries out of every hundred it is presently cheaper to produce a model by
a means other than Rapid Prototyping. It could therefore be asked what future has it? The
benefit is its rapidity; and the changes in the design and production cycles that can be made
with the availability of prototypes. A prototype model is a form of high fidelity and non

specialist communication - if a picture is worth a thousand words then a model is worth a
book.
4.3.1. Concurrent Engineering
The influences of competition, customer demands and of rapid technological development,
are all fuelling the need for reduced time to market. The Thorn Lighting Group has the
experience of the Type-E Ballast to reinforce this. Reduced time to market maximises
revenue and also allows the product life cycle to be condensed. The benefit of the latter is not
obvious. Imagine two competing companies: one that develops short life cycle products
rapidly; and another that develops longer life cycle products more slowly. The slower
company shall be given the advantage of starting off with the technically superior product.
The fast company can close up from behind by mimicry. The companies are now almost
level. The slow company must develop its products in quantum leaps to maintain superiority -
this is difficult and costly. The fast company can evolve their product in small steps - the
philosophy of continuous improvement. This type of development is easy and cheap8. The
fast company can ease ahead of the slower one. The slow company is now chasing but they
cannot develop as quickly. The most likely coarse of events is that the slow company will fall
behind at an ever increasing rate. The slow company needs a miracle product to close the gap
once a few product generations are put between the companies. This scenario is the ongoing
history of the Japanese car industry.
The cornerstone of the fastest approach possible is the catch all ‘Concurrent Engineering’.
This is easiest to describe in terms of what it is not. It is not a linear approach: concept design,
detail design, testing, production engineering and finally production. Any delays accumulate
in the linear approach; at the same time any down stream feedback is slow - a production
engineering problem could necessitate a concept design change that would make all the
intervening work a waste of money and equivalent to one huge delay. The concurrent
approach involves work on all the stages at the same time. The idea is that the production
engineering problem would be realised early before any of the intervening stages is complete.
The concurrent approach also causes the delays in each of stages to be in parallel rather than
end to end. A concurrent approach is only possible with rapid and fluent communication
between all the activities.
Rapid Prototyping is a method of rapid and fluent communication above all else9. Its
application to this effect is described in the following sections.
4.3.1.1. Testing
Testing can reveal problems with a design. It is therefore desirable to carry out such testing as
early as is possible. The earliest possible testing can be carried out on prototypes that are
produced rapidly. The main problem areas in the testing of Thorn Lighting's products are
thermal and ingress testing. It is therefore for these tests that it would benefit the company to
use Rapid Prototyping. The models should be produced from the ‘first draft’ designs rather
8 The small changes mean that the designs can be ‘right first time’ and are therefore unlikely to suffer delays.
This in turn stops cost from escalating.
9 The exception is testing. In this the model is an inherent part of the process.

than later ones - resizing a reinforcing flange is unlikely to drastically effect the thermal
testing. The different aspects of the design can separately work through the cycle of design,
model, test, design, model test, etc. These different aspects, e.g. a cover plate seal and a lamp
holder bracket can therefore be developed concurrently if it is possible to produce the models
- which is where Rapid Prototyping steps in.
There are some issues to remember when using Rapid Prototyping for testing. Namely, the
models are generally not made from production component materials. In cases when they are
the Rapid Prototyping form of the material will have slightly different properties to the
production material10. Fortunately these discrepancies due to material differences are
consistent; even between different processes. The Rapid Prototyping material can be
described as:
• Weaker
• Less stiff
• Less dense
• Having a lower maximum service temperature
• Less thermally conductive
Therefore testing with the model builds in a big safety factor. The biggest problem is the
maximum service temperature and live testing with wound gear - the models could distort,
melt or even burst into flames dependent upon the Rapid Prototyping process selected. The
solution to the testing shortcomings is to replication cast in a closely matched material, or to
choose a process that produces a model in a closely matched material.
4.3.1.2. Production and Standards Engineering
The production engineering function currently works from two dimensional orthographic
drawings. These are currently produced later than a ‘first draft’ Rapid Prototyping model
would be possible. Production engineers are more than capable of interpreting such drawings;
but a model helps the communication process - they are more likely to spot a potential
problem or a possible improvement on a model than they are on an orthographic drawing.
4.3.1.3. Assembly
Prototypes allow mock assembly operations to be carried out. They also allow something that
it is not currently possible - design communication with the shop floor. There is no greater
expertise on the assembly of the company's products than the combined experience available
on the factory floor. This wealth of knowledge is only just being tapped by the formation of
10 The SLS process from DTM can produce polycarbonate models. A production component would be injection
moulded. This would make the material equivalent to 100% sinter density; while it would also form flow line
related stress. In contrast the Rapid Prototype model would have a 70-80% sinter density. This would make it
weaker and less dense but more brittle. At the same time it would also reduce the components maximum
operational temperature.

Continuous Improvement teams; but these can only make a contribution after production has
started - a concurrent approach requires that their knowledge be available from the start. The
factory floor would have no problem relating to a Rapid Prototyping model; the beauty of
such a model is that nobody in or outside the company has a problem relating to it.
All standards testing that was not material dependent could be completed during the
development cycle rather than afterwards.
4.3.1.4. Packaging
This is developed very late in the process where it may cause a delay. Earlier access to Rapid
Prototyping model would allow the packaging to be finalised; hence eliminating any
possibility of delay.
4.3.1.5. Marketing
There are several ways in which Rapid Prototyping is beneficial to the marketing department.
Rapid Prototyping may be directly by the marketing function. They can use it for market
research by talking to the customers and the sales force. This body of knowledge is not
currently used to the fullest.
The company presently has a problem with market brief ‘changing’ during the development
of a product. This can be due to the market position changing during the present long
development period; though the more common problem is communication. The marketing
people need to see a prototype to really relate to the design. It is at this stage that they may
want to change something. Presently this point is quite close to the potential completion of
the design and therefore any changes effectively create long delays. This problem could be
solved by showing the product manager a ‘first draft’ model. Minor adjustments after the
‘first draft’ are not of interest to the product manager. If the product manager okayed a model
then they could be held to that.
4.3.2. Right First Time
Rapid Prototyping is not about shaving a few days off the development cycle by providing an
alternative route to making a final design verification prototype. It is about Concurrent
Engineering and the Right First Time principle. Rapid Prototyping models are a
communication aide; and communication is the key to Right First Time.
4.3.2.1. The Son Pak
This project had some Rapid Prototyping quotations that are discussed in section “3.2. The
Son Pak”. These quotations were for a late design verification prototype. The history of the
development can be summarised as:
• 1 month to complete concept design.

• 7 months to complete detail design.
• design review.
The design review rejected the concept design - thus turning 7 months work into a 7 month
delay. A ‘first draft’ model reflects the concept design. It is difficult to say how long it would
take to get from the concept design complete stage to the ‘first draft’ model stage - but it
would not have taken the 7 months. This would have shortened the delay caused by the
rejection in the design review. If the concept had been accepted then the design could still fail
at the testing stage. A model could have been tested - hence the next hurdle would have been
eliminated at the same time!
4.3.2.2. Competitive Designs
Designs can compete both internally and externally. First consider external competition -
biding for a contract. The company believes in high technology bid support - it has developed
the Visualisation system for lighting schemes. A model is an essential aide to a bid; therefore
a high technology model cannot fail to impress potential clients. Rapid Prototyping could be
used to supply several designs for the same bid.
The other potential area of competition is internal. Presently a brief is assigned to an
individual who comes up with ideas for the concept design. This limits the pool of ideas the
design develops from. An alternative suggested to the author is that a brief be thrown open to
internal competition for the concept design by a deadline. The designs would be presented
and the individual who would progress the design would then be selected. They would then
go off and redo the concept design borrowing any useful ideas from the competing designs.
This process would increase the pool of ideas several fold.
A concept that has competed wins more acceptance. This is important for rapid development.
An individual, say a product manager can have slight reservations about a design that will be
apparent at a subconscious level. The single design will do, but they feel it could be improved
in some unknown way. The development of this design could be indecisive and subject to
petty change in these circumstances. If a design competes and it is then selected, then in the
eyes of the selector the design is the best - especially if it is developed to incorporate the best
aspects of the competition. Such a design cannot be changed much because most of the
alternative ideas have already been presented and rejected.
The internal competition approach can be implemented without Rapid Prototyping. It will be
a long time in the future that the costs would be low enough to allow Rapid Prototyping to be
used as a competitive internal presentation aide. The point is that it is important to win
acceptance of the design from all the individuals involved. A model can be used after the
competitive stage to win over any reservations. Access to a model would help any dissenting
individuals to constructively voice their subconscious reservations. The value of this last
point cannot be overlooked. The approach has a much greater likelihood of being ‘Right First
Time’.

5. THE FUTURE
5.1. THE INTERFACE
The STL interchange format can only have a limited future because of the problems described
in section “2.1.2.2. STL Manipulation by the Specialist”. Probably the longest term
development is by the Brunel University Consortium. The objective of this is to develop an
intelligent converter between STEP and any form of proprietary Rapid Prototyping format,
e.g. STL. Any manipulation required is carried out by the converter using the original STEP
data. This avoids the problems of using a more limited Rapid Prototyping format. The
intelligence of the converter would optimise the model, e.g. facet densities in the case of
STL.
Is this of any use to the Thorn Lighting Group? The STEP format is the long term future of
CAD. The company has two three dimensional CAD systems: ME30 and only recently, Solid
Designer. Neither of these use STEP; however Hewlett Packard is developing a STEP
interface for Solid Designer. This will be demonstrated late in this year. The most important
aspect of such a system is what it can do for Rapid Prototyping's major limitation - surface
finish. It would also be useful if it automatically generated supports if necessary; and
automatically packed a machine with multiple parts as efficiently as is possible. If the
company feels that it needs to redirect any research to better suit its own needs, then it should
join the appropriate consortia.
5.2. PROCESSES
The future of Rapid Prototyping systems will split down two pathways that shall be referred
to as ‘high end’ and ‘low end’ in this report. All the machines currently available are high
end, i.e. expensive. These will develop to the high fidelity systems required for Rapid Tooling
as described in section “4.1.2. Rapid Tooling”. The requirements for testing favour processes
that can model in the correct materials. Therefore the selective laser sintering process is
probably the process with the longest future. DTM is current working on partially sintering
ceramics and metals in new machines. The high end of the market will also see the
introduction of spray metal deposition processes.
The low end of the market is not yet available, but imminent. These are the desktop machines
that become CAD terminal peripheries. This market was created by the US Ford Motor
Company when it claimed that they would equip every designers' workstation throughout
Ford with one of these systems, provided that they cost less than $30000. Ford have a very
large number of workstations! Models produced on low end would not have good material
properties but they would be cheap.
The low end processes are generally referred to as 3D Printing. This name belongs to a
process developed by MIT. It is used in the Soligen machine presently but it is expected that
it can be put to low end use. The name is unfortunate because it is much better suited to some
alternative technologies. These are based on inkjet techniques: the model is sprayed down in
layers along with a support material. These shall be given the name ‘twin jet processes’

throughout the remainder of this report. The 3D Printing process by MIT is a more general
form of the process described in section “2.2.5. Selective Binding”.
Low end processes lower the barriers to entry into Rapid Prototyping techniques. It is difficult
to say how useful they are to the Thorn Lighting Group. The specifics of the products are not
known to the author; but the low end processes are likely to have the following traits:
• Low end models will have material properties that are worse than high end processes.
This point has a high degree of certainty.
• Low end processes are likely to be capable of producing small components only. It
should be remembered that the processes are aiming at desktop application. A
successful technique may be expanded to a larger machine in the longer term.
• Low end does not necessarily mean a low quality finish. The machines may or may
not start with low quality finish to reduce costs. Ironically it is probably easier to raise
the quality of the low end processes than it is the various high end ones. Quality is
therefore a complete unknown regarding low end processes.
The new suppliers and technologies known to the author are summarised in the following
table. This contains information on both high end and low end processes.
Table 10 ‘New Rapid Prototyping Systems’.
Supplier Product Details
DTM New
machines
Ceramic and metallic modelling facilities.
The models are selectively sintered to a
low sinter density; then they are fired in a
post processing operation to achieve full
density.
The ceramics are coated with a material
that selectively sinters more easily than a
pure ceramic.
BPM
Technology
(Incre Inc.)
BPM (previously Perception Systems) is
developing a twin jet product. BPM stands
for Ballistic Particle Manufacture.
Incre Inc. has a spray metal process that
uses technology licensed from BPM. This
represents a large diversity of expertise on
the part of BPM.
Texas
Instruments
ProtoJet Twin jet process.
Visual Impact
Corp.
Sculptor Twin jet process.
Carnegie
Mellon
(Research) Spray metal techniques for Rapid Tooling.

5.3. SPECIALIST PRODUCTION
Rapid Prototyping's freeform geometric capabilities give it a unique production capability. It
is capable of producing components that are impossible to manufacture any other way. The
applications of this are only limited by one's imagination. Two broad groups of applications
are apparent: articulation and structural. The articulation applications are sealed units with
moving parts, e.g. a high strength ball and socket joint. The structural applications are more
versatile; these will probably be used by the aerospace industry in the not too distant future. It
will be possible to produce structural components with higher stiffness to weight ratios than
are currently possible. This will be achieved by producing shapes with extremely complex
internal geometries - three dimensional honeycomb and sponge like constructions. This is the
construction that nature uses for the high stress areas in bones. For these applications the
component must be built directly in the required material because replication processes are
not feasible. Selective laser sintering would generally not be suitable - this application will
mostly be the province of spray metal techniques.
Such production applications are high cost, high performance. It is unlikely that the Thorn
Lighting Group will need these capabilities.

6. CONTACTS
Supplier Contact Details
3D Systems Inc. Ltd Andrew Chantrill
Unit 7, The Progression Centre,
Mark Road,
Hemel Hempstead,
Herts. HP2 7DW.
(0442)66699
(0442)234535 (fax)
Richard Aubin of United Technologies (Pratt & Whitney).
0101 203 727 1697
He did not return my call regarding contacting
the Visual Impact Corporation.
BPM Technology Box 8002,
1110 Powdersville Road,
Easley,
SC 29640.
0101 803 282 0033 They are 5 hours behind.
They did not return my call.
Bridgeport Machine Tools Jez Luing.
(0533)531122
(0533)539960 (fax)
Brunel University Consortium Consists of:
the university - Prof. A.J. Medland,
CIMIO Ltd.,
Formation Engineering Services Ltd.,
Rolls Royce Ltd.,
Metal Box Plc.,
For contact see Prof. A.J. Medland
California Polytechnic State
University
For contact see Mr Martin Koch
Carnegie Mellon Institute Len Weiss.
Pittsburgh.
CMET No details known.

CIMIO Ltd. Supplier of STEP integrated CAD facilities.
Adrian Laud, Managing Director.
Brunel Science Park,
Coopers Hill Lane,
Englefield Green,
Surrey. TW20 0JZ
(0784)438038
(0784)472870 (fax)
Cranfield Institute of Technology (0324)750111
Cubital Ltd. Israel
13 Hasanda St.
(P.O.B. 2375),
Industrial Zone North,
Raanana, 43650
Israel.
010 972 52 906888
010 972 52 919987 (fax)
Germany
Liebigstrausse 3,
6369 Nidderau-Heldenbergen,
Germany.
01049 6187 22037
01049 6187 25155
Dr P.M. Dickens (The most prolific UK academic on the subject
of Rapid Prototyping)
Department of Manufacturing Engineering and
Operations Management,
University of Nottingham,
University Park,
Nottingham. NG7 2RD
(0602)514063
(0602)514000 (fax)
DMEC No details known.

DTM Corporation Bureau services USA
Kent Nutt, Marketing Manager.
161 Headway Circle,
Building Two,
Austin,
Texas 78754.
USA.
0101 512 3392922
0101 512 3390634 (fax)
Germany
Klauss J. Eβer
01049 210352265 (fax)
EOS GmbH Johann Oberhofer
Pasingerstrasse 2,
D-8033 Planegg bei Münich,
Germany.
01049 89 8991310
01049 89 8598402 (fax)
Formation Engineering Services Ltd. Mr J.R. Andrzejewski, Systems Manager.
Nigel Bethell (regarding materials etc.)
Unit A3, Spinnaker House,
Hempsted,
Gloucester,
Gloucestershire. GL2 6JA
(0452)380336
(0452)380497 (fax)
Geoff Lart of ProtoMod Ltd.
(0234)750875 (fax)
For the phone number see Cranfield Institute of
Technology.
Helisys Inc. 2750 Oregon Court,
Building M-10,
Torrance,
CA 90503.
USA.
0101 310 782 1949
0101 310 782 8280 (fax)

IMechE Seminar papers - Rachel Parkinson
Library - Millie Fitzgerald
Inter library loan - Miss Emily Lloyd
(071)2227899
(071)2228762 (Library fax)
Incre Inc. Dave Gore, President.
Corvallis,
Oregon.
Mr Martin Koch Research into Rapid Tooling
Industrial Engineering Department,
California Polytechnic State University,
San Luis Obispo,
CA 93407.
USA.
Faxed response lost.
Light Sculpting Inc. 4851 North Marlborough Drive,
Milwaukee,
WI 53217.
USA.
010 414 964 9860
Massachusetts Institute of Technology 77 Massachusetts Avenue,
Cambridge,
MA 02139.
USA.
010 617 253 5381
Prof. A.J. Medland of Brunel Consortium
Centre for Geometric Modelling and Design,
Department of Manufacturing and Engineering
Systems,
Brunel University,
Uxbridge,
Midds. UB8 3PH
(0895)274000 #2943
(0895)812556 (fax)
Dr Unny Menon Rapid Prototyping authority at CALPOL.
For contact see Mr Martin Koch
Mitsubishi No details known.
Nottingham University For contact see Doc. P.M. Dickens

Quadrax Laser Technologies Inc. 300 High Point Avenue,
Portsmouth,
RI 02871.
USA.
010 401 683 6600
Rolls Royce No details known.
Rover Group Graham Tromans
Stereolithography,
Building 41,
Fletchampstead Highway,
Canley,
Coventry. CV4 9DB
(0203)874086
(0203)874750 (fax)
RP&T Consortium David Wimpenny,
Lee Styger.
Advanced Technology Centre,
University of Warwick,
Coventry. CV4 7AL
(0203)523687
(0203)523387 (fax)
Schneider No details known.
Sherbrook Automotive Ltd. Richard C. Smith, Sales Manager.
Sherbrook House,
Swan Mews,
Lichfield,
WS13 6TX
(0543)257131
(0543)263816 (fax)
(0753)864898 (home base - phone/fax)
Soligen Inc. Chick Lewis, Vice President.
Northridge,
California.
Sony No details known.

Stratasys Inc. 14950 Martin Drive,
Eden Prairie,
MN 55344-2019.
USA.
0101 612 937 3000
0101 612 937 0070 (fax)
Kevin Stubbs of Thorn Lighting Group
3, King George Close,
Eastern Avenue West,
Romford,
Essex. RM7 7PP
(0708)730888
(0708)727370 (fax)
(0831)304715 (car)
7-268-6252 (internal network)
Teijin Seiki Co. Ltd. Kenichi Ikari
Shinjuku NS Bldg.
4-1, 2-Chome,
Nishishinjuku,
Shinjuku-ku,
Tokyo. 163-08
Japan.
01081 3 3348 2227
01081 3 3348 1050 (fax)
Texas Instruments Inc. Steve Penn, Project Manager.
McKinney,
Texas.
Umak Bureau and sole UK agent to Helisys.
P.H. Graham, Managing Director.
BSA Business Park,
Armoury Road,
Birmingham,
Midlands. B11 2RQ
(021)766 8844
(021)766 8998 (Fax)

Visual Impact Corporation George McKinney, Director.
Windham,
New Hampshire.
International directory enquiries cannot locate
them.
Warwick University For contacts please see RP&T Consortium
Table 11 ‘Contacts’.

7. RECOMMENDATIONS
Rapid Prototyping can either be used as part of a Concurrent Engineering strategy, or it can be
used as a simple prototyping tool for some companies' products. The best examples of the
latter are engine manifolds. There is no such application within the Thorn Lighting Group as
is the case for most companies. There are tremendous opportunities however as part of a
Concurrent Engineering strategy.
7.1. THE SHORT TERM
The Thorn Lighting Group is not ready to take advantage of Rapid Prototyping. The company
has a target development time that it should achieve by other means. Applying Rapid
Prototyping techniques now will not have sufficient benefit to justify the costs. Model
production time is not the limiting factor of the current system. The company must more fully
develop its concurrent approach. When the company has achieved the current target it will be
ready to take advantage of Rapid Prototyping to halve the development time from the present
target!
In the mean time it will be possible to apply Rapid Prototyping on a project by project basis.
In order for this to be effective the designers must be aware of the issues described in section
“2.1. Model Production”. The success rate of this application will be low - as testified by the
quotations in section “3. Trials”. The most likely area for success in the short term is in
Custom Products for large projects, such as the Jubilee Line Extension.
The most important objective in the short term is spreading awareness of Rapid Prototyping
throughout the company.
7.2. THE LONG TERM
The pressures that will drive the company to Rapid Prototyping are described in section
“4.3.1. Concurrent Engineering”. Now is not necessarily the time to get on board, but it is
certainly the time to try to develop the company's Concurrent Engineering techniques in
preparation. ‘Come the revolution’ the company does not want to be a slow one in a fast
moving world. Before this the company should try to maximise its current resources of CAD
visualisation and concept drawings. As soon as the company does this Rapid Prototyping will
drift in as long as people are aware of it.
The Thorn Lighting Group is striving to be a World Class company. At this time Rapid
Prototyping is a technology that is above World Class. In a short time it will descend to a
World Class technology. This is the point when the Group should be ready to take up the
technology seriously. In the more distant future Rapid Prototyping could become a necessity
for survival.
The best scenario is for the company to develop its concurrent approach over the next two
years. If this was successfully completed then the timing to buy a machine would be perfect.
The low end market should have developed; while the first metal capability machine from

DTM would be available - sole UK user of this would represent a very interesting bureau
opportunity. Investment in plant before the company has met its current target, even in two
years time, would be a mistake.

8. CONCLUSIONS
The most general conclusions are to be found in the report's recommendations. The most
immediate point is that there is a need for people to be aware of this new technology. The
reader is directed towards section “1.3. What is Rapid Prototyping?” for a general description.
Designers should be aware of the issues raised in section “2.1. Model Production” while the
management needs a perspective on sections “4. Approaches” and “5. The Future”. The rest
of the report is reference material.
It is felt that the report has been successful in all its objectives. It had been hoped that more
could be done in the way of concrete financial justification, but the company has not recorded
the information that would be required. It may be possible to analyse some future projects, but
people are defensive about the type of information required.
In summary it can be concluded that this exercise was worthwhile. Rapid Prototyping is a
technology that the company needs to be aware of, and that in all likelihood will play a part in
its World Class future.
Document Reference:
Filename: RP2.DOC
Printed on: 19/03/13

INDEX
FIGURES
1. ‘Free Hand Sketch of a Non 3 Axis Geometry’.................................................................6
2. ‘Lamina Model Construction’............................................................................................7
3. ‘Stacking in a Rapid Prototyping Machine’.......................................................................10
TABLES
1. ‘Currently Available Rapid Prototyping Machines’. .........................................................19
2. ‘Chrysler's Rapid Prototyping Benchmark’. ......................................................................20
3. ‘UK Rapid Prototyping Bureaux’. .....................................................................................21
4. ‘Popular Pack Spine End Cap History’..............................................................................22
5. ‘Ian Thorniwell's Son Pak Quotations’..............................................................................23
6. ‘Rover Group's Quotation for the Adagio Arm’. ...............................................................24
7. ‘Formation Engineering's Quotation for the Adagio Arm’................................................25
8. ‘Cost of the Two Halves of the Adagio Arm without Using Rapid Prototyping’..............25
9. ‘Quotations for Jubilee Line Extension Platform Fittings’................................................27
10. ‘New Rapid Prototyping Systems’...................................................................................40
11. ‘Contacts’.........................................................................................................................46
PLATES
1. ‘The Adagio Arm (half)’....................................................................................................24

GENERAL INDEX
3
3D Printing............................................38
3D Systems .........................11, 17, 21, 41
SLA Machines...............17, 21, 23, 27
A
Adagio Arm ..................22, 23, 24, 25, 26
Aircraft Carrier......................................31
B
Ballistic Particle Manufacture...............40
BPM Technology............................40, 41
Bridgeport .........................................6, 41
Brunel University Consortium........38, 41
C
California Polytechnic State
University..........................................41
Carnegie Mellon....................................41
Chrysler Motor Corporation............19, 20
Ciba-Geigy............................................17
CIMIO Ltd. ...........................................42
CMET .............................................19, 41
CNC Machining..........................5, 25, 29
Coca Kola................................................6
Competitive Designs.............................36
Concurrent Engineering 28, 29, 33, 35, 47
Cranfield Institute of Technology.........42
Cubital.................................17, 19, 21, 42
Curved detail.........................................10
D
DMEC.............................................19, 42
DTM..............................18, 23, 38, 40, 43
du Pont ..................................................18
E
Electrode Discharge Machining
(EDM) .........................................30, 31
EOS.................................................18, 43
F
Field Repairs.........................................31
Ford Motor Company ...........................38
Formation Engineering Services21, 23, 25, 35, 43
Freeform Geometry.........................28, 40
Fused Deposition Modelling.................17
G
Geometry.....5, 6, 8, 11, 12, 13, 15, 25, 28
H
Height..............................................10, 11
Helisys.......................................18, 21, 43
Hewlett Packard........................13, 21, 38
I
IMechE..................................................44
Incre Inc. .........................................40, 44
J
Jubilee Line Extension..............26, 27, 47
L
Laminated Object Manufacture ............23
Laminated Object Manufacture
(LOM) .................15, 18, 21, 23, 26, 30
Light Sculpting Inc..........................18, 44
M
Massachusetts Institute of
Technology............................18, 38, 44
Material Properties........14, 15, 31, 38, 39
Mazda....................................................28
ME30 ....................................................38
Mitsubishi .......................................19, 44

N
Nottingham University..........................44
O
Orientation ........................................9, 11
Overhangs ...............................................9
P
Post Curing............................................14
Prosthetics.............................................28
ProtoJet .................................................40
Q
Quadrax Laser Technologies Inc.....19, 45
R
Renault....................................................6
Rolls Royce.....................................21, 45
Rover Group............21, 24, 26, 27, 32, 45
RP&T Consortium ....................21, 32, 45
S
Schneider.........................................21, 45
SCS .......................................................19
Sculptor.................................................40
Selective Laser Sintering (SLS)14, 15, 16, 18, 38, 40
Sherbrook Automotive........21, 23, 27, 45
Solid Creation System...........................19
Solid Designer.......................................38
Solider...........................17, 19, 21, 23, 27
Soligen ......................................18, 38, 45
SOMOS.................................................18
Son Pak ...........................................23, 36
Sony ................................................19, 45
SOUP ....................................................19
Space Station.........................................31
Spray Metal Techniques..................38, 40
STEP .....................................................38
Stereolithography..................................13
STL File Format............11, 12, 13, 23, 38
Stratasys ..........................................17, 45
Surface Finish .......................7, 12, 29, 38
T
Teijin Seiki......................................18, 46
Testing ....................22, 33, 34, 35, 36, 38
Texas Instruments...........................40, 46
Twin jet processes...........................39, 40
Type-E Ballast ......................................33
U
Umak.........................................21, 23, 46
V
Visual Impact Corporation..............40, 46
W
Warwick University........................21, 46
X
Xedos 6 .................................................28

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