Early prototyping using 3D printing and CNC machining can increase your speed to market. Learn about key design considerations and benefits of using both processes as well as injection molding during early prototyping stages.
Taking prototyping one step further, we will discuss how using low-volume injection molding for engineering-grade parts can help bridge you into large-scale production. You will learn valuable design considerations that are often overlooked in early product development that concern draft, wall thickness, coring, material selection and rib design.
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Prototype Smarter – transitioning to production faster and more effectively
1.
2. q This webinar will be available afterwards at
www.designworldonline.com & email
q Q&A at the end of the presentation
q Hashtag for this webinar: #DWwebinar
Before We Start
3. Meet your Speakers
MODERATOR FEATURED SPEAKER
Tony Holtz
Technical Specialist
Proto Labs
Leslie Langnau
Managing Editor
Design World
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§ What are you making?
§ What is its function?
§ What will be the material?
§ How many will you need?
§ What is your expected price?
Second
First
§ How do you want the parts manufactured?
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3D CAD
Form + Fit
Testing
Functional
Testing
Low
Volume
High
Volume
Design for Production
CAD allows us to design with production in mind
3D Printing CNC Machining Injection Molding
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3D Printing: Desktop vs. Industrial
§ Desktop
§ Hobbyists or concept of design
§ Fast and easy to use
§ Poor surface finishes and small build frame
§ Responsible for maintenance, scheduling and limited material
§ Industrial
§ Applications range from prototypes to production parts
§ Engineering-grade materials available
§ Thermoplastics, rubbers and metals
§ High and micro-resolution possible
§ Good surface finish; multi-colored and secondary finishing available
§ Service bureau maintains maintenance, scheduling and material to avoid
downtime
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Design Considerations for DMLS
§ Support structures
§ Overhangs
§ Self-supporting angles
§ Bridges
§ Internal stress and warpage
§ Channels and holes
§ Internal features
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§ DMLS parts require
supports to connect part
to platform and hold
features in place
§ Supports prevent part
from warping during
rapid melting and
cooling process
Support Requirements
Photo courtesy of Concept Laser.
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§ Design large, flat, down-facing surfaces
§ Work with manufacturer for proper part orientation
§ If orientation is locked, create features that are
“self-supporting”
§ Reduce hole diameters or create diamond- or tear
drop-shaped channels instead of round
§ Minimize the amount of overhang — use proper
angles or decrease the gap between features
Minimizing Supports
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§ Unlike other additive processes,
DMLS has a small allowance for
unsupported overhangs (0.020 in./
0.5mm)
§ If left unsupported, large overhangs
may lead to build crash or
deterioration of part detail
Overhangs
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§ A bridge is any flat
down-facing surface
that is supported by
2 or more features
Bridges
§ Minimum allowable
unsupported bridge
distance is small
(~0.080 in./2mm)
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§ Changes in cross-sectional areas can lead
to warpage between features
Internal Stress and Warpage
DESIGN TIP: Use solid connections between sharp changes in
cross-sectional area, and then remove with secondary operations
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§ Channels and holes are
self-supporting features
§ Great for conformal
cooling applications
Channels and Holes
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Channels and Holes
§ As the hole diameter increases,
the overhangs increase near the
closing of the hole
§ Unsupported holes larger than
0.31 in. (8mm) diameter will suffer
downfacing distortion or curl,
potentially creating other build
issues
DESIGN TIP: Use diamond or
tear drop shapes for larger diameter
channels
Hole diameters in mm
15 12 10 8 6 5 4 3 2 1
15mm
(0.6 in.) 12mm
(0.47 in.)
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§ A huge benefit of DMLS is the ability to create complex internal features
§ Channels, overhangs, self supporting angles and bridge dimensions must
all be taken into consideration when designing areas that may be hard to
access
§ If an internal feature requires supports but allows no access, the supports
remain inside, and the geometry may not function as intended
§ Accessibility for powder removal should also be taken into consideration
DESIGN TIP: Lattice structures can be used internally to reduce weight and
provide support
Internal Features
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Design Considerations for SL
§ Horizontal holes
§ Overhang supports
§ Sharp points
§ Build orientation
§ Support structures
§ Holes
§ Microfluidics
§ Replacing metal with metal-plated SL
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Holes:
§ Ø 0.020 in. Normal Res
§ Ø 0.015 in. High Res
§ Ø 0.008 in. Micro Res
Channels:
§ 0.025 in. for High Res
§ 0.013 in. for Micro Res
Small Gaps: (negative spaces)
§ <0.025 in. can seal shut and
should be reviewed
Feature Recognition
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Microfluidics Sidewall surfaces will be moderately clear, but will have
distortion from the layer lines. These surfaces are slightly
more clear than downfacing, non-substrative surfaces. Typically upfacing surfaces will be the most clear
Downfacing surfaces that are not in contact
with the substrate will be moderately cloudy
due to the overcure on downfacing surfaces.
If built on a substrate, surfaces flush to the
substrate will be comparably clear to upfacing.
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Stereolithography Compared to Injection-Molded PC
Accura 5530 Accura 60 Somos NanoTool PC (Molded)
Hardness, Shore D 88 86 94 118-120 (R-Scale)
Heat Deflection 338-482° F 127° F 185-437° F 250-280° F
Tensile Strength 47-61 MPa 58-68 MPa 66-80 MPa 50-72 MPa
Flexural Strength 96-108 MPa 87-101 MPa 103-149 MPa 82-93 MPa
Stereolithography Compared to Injection-Molded PP
Accura Xtreme White Somos 9120 PP (Molded)
Hardness, Shore D 78-80 80-82 80-100 (R-Scale)
Heat Deflection 117° F 126 - 142°F 124-203° F
Tensile Strength 45-50 MPa 30 - 32 MPa 27-40 MPa
Flexural Strength 75-79 MPa 44-46 MPa 41 MPa
Stereolithography Compared to Injection-Molded ABS
RenShape 7820 MicroFine Green Somos Watershed ABS (Molded)
Hardness, Shore D 87 85 -- 109 (R-Scale)
Heat Deflection 122° F 138° F 115-130°F 185-215° F
Tensile Strength 39-51 MPa 45 MPa 47-54 MPa 32-42 MPa
Flexural Strength 62-80 MPa 74 MPa 63-74 MPa 60-72 MPa
Know the Material Properties
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Replacing Metal with SLArmor
Stereolithography compared to Die-cast Aluminum
SLArmor Die-cast
Aluminum10% metal volume 20% metal volume 30% metal volume
Heat Deflection 122-516° F >500° F
Tensile Strength 100 MPa 145 MPa 200 MPa 300 MPa
Elongation at Break 0.9% 1.04% 1% 2-5%
Mod. Of Elasticity 21,000 MPa 31,000 MPa 42,000 MPa 70,000 MPa
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CNC Machining
§ Processes for CNC machining include milling, turning,
routing, and lasers and plasma cutting
§ Wider range of materials versus 3D printing
§ Material properties comparable to injection molding
§ More established technology than 3D printing
§ Higher quantities and surprisingly faster
lead time over 3D printing
§ Challenges can occur with complex geometries,
endmill sizes and fixturing
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Injection Molding
§ You prototype with 3D printing and CNC machining, so why
not with injection molding?
§ Low-volume injection molding provides actual molded
thermoplastics the same way your production parts would
be produced
§ 25 to 10,000+ parts are typically possible from rapid
aluminum tooling
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Material Selection
Characteristics to consider when selecting a material:
§ Chemical resistance
§ UV concerns
§ Temperature
§ Flammability
§ Strength
§ Stiffness
§ Impact resistance
§ Compatibility
Characteristics to consider during design process:
§ Warp
§ Sink
§ Porosity
§ Assembly
§ Material memory
§ Appearance
§ Tolerance
§ Gate and ejection
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Material Selection
Resin generic name Some brand names Strength Impact resistance High temperature Relative cost
Acetal Delrin, Celcon Medium Medium Medium-Low Medium
Nylon 6/6 Zytel Medium High Low Medium
Nylon 6/6, glass filled Zytel High Medium High Medium
Polypropylene Maxxam, Profax Low High Low Low
High Density
Polyethylene (HDPE)
Dow HDPE, Chevron HDPE Low High Low Low
Polycarbonate Lexan, Makrolon Medium High Medium High Medium High
Acrylonitrile Butadiene Styrene
(ABS)
Lustran, Cycolac Medium-Low High Low Low
Polycarbonate/ABS Alloy Cycoloy, Bayblend Medium High Medium Medium
Polybutylene Terephthalate Valox, Crastin Medium High Low Medium High
Polybutylene and Polyethylene
Terephthalate, glass-filled
Valox, Crastin, Rynite High Medium Medium Medium High
Polystyrene Styron Medium-Low Low Low Low
Thermoplastic Elastomer Isoplast, Santoprene Low High Low Medium-Low
Acrylic Plexiglas, Acrylite Medium Low Low Medium
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Wall Thickness by Resin Type
The table shows wall thickness that Proto Labs recommends according to resin. Please note that thin
walls only work on small parts and thicker walls are required where the resin has a long way to flow.
Proto Labs makes parts with dimensions of about 0.25 in. to 29.6 in. (6.3mm to 752mm).
Resin Inches
ABS 0.045 – 0.140
Acetal 0.030 – 0.120
Acrylic 0.025 – 0.500
Liquid crystal polymer 0.030 – 0.120
Long-fiber reinforced plastics 0.075 – 1.000
Nylon 0.030 – 0.115
Polycarbonate 0.40 – 0.150
Polyester 0.025 – 0.125
Polyethylene 0.030 – 0.200
Polyethylene sulfide 0.020 – 0.180
Polypropylene 0.025 – 0.150
Polystyrene 0.035 – 0.150
Polyurethane 0.080 – 0.750
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Core out parts to eliminate thick walls
You get the same functionality in a well-molded part.
Original
Geometry
Cored Geometry
Coring Out Thick Area
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Thermoplastic
LSR / Elastomeric
Metal Die Casting
Metal Sand Casting
Machining
3D printing
1-3°
1-3° (hand removal)
3-5° minimum
5-7° minimum
0° possible (but not recommended)
0° possible (but not recommended)
Recommended Draft
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Part Design
§ What is its function?
§ What are your preferred materials?
§ How many parts do you need?
§ What is your budget?
51. Questions?
MODERATOR FEATURED SPEAKER
Tony Holtz
Technical Specialist
Proto Labs
customerservice@protolabs.com
@ProtoLabs
Leslie Langnau
Managing Editor
Design World
llangnau@wtwhmedia.com
@DW_3DPrinting
52. q This webinar will be available at
designworldonline.com & email
q Tweet with hashtag #DWwebinar
q Connect with Design World
q Discuss this on EngineeringExchange.com
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