Palestra 4 - Avanços em tecnologia de fresamento: do fresamento convencional para o HSC.

Advances in milling Technologies:
from conventional milling to HSC
Benedikt Gellissen

Fraunhofer-Institut für Produktionstechnologie IPT

International Seminar: Application of new technologies in
the metal mechanic sector

Joinville, Brazil, September 2011
© WZL/Fraunhofer IPT

Outline of the presentation
1 What is the motivation for advanced milling technologies

2 What is required to realize a successfull implementation of HSC?

3 Advanced roughing possibilities

4 Improved finishing results due to intelligent CAM-Systems and tool adaption

5 Conclusion

© WZL/Fraunhofer IPT Page 1

Importance of the milling technology for the molding industry -
Comparability of tool types and use of technology
Injection moulding Solid forging Deep drawing Stamping and bending

Special features Special features Special features Special features
n Surface n Material (Temperature) n Surface n Material
n Precision n Edge zone n Precision n Precision
n Filigree n Precision n Geometrie n Surface

Process Process Process Process
Milling Milling Milling Milling
Turning Turning Turning Turning
Grinding Grinding Grinding Grinding
Sink EDM Sink EDM Sink EDM Sink EDM
Wire EDM Wire EDM Wire EDM Wire EDM
Importance Importance Importance Importance

Prismatic tool
Focus free-form surfaces
components

Driver »tool steel«: Improved materials for the industry
Impact of the defect size on the bending resistance
Aims
bending resistence
σb
[kN/mm2] powder metallurgical
n Reaching an
homogeneous structure
4
n Low corn and carbide size
for improved wear
conventional forging resistance and strength
3
n Reduction of material
anisotropy in case of
2 manufacturing
conventional founded

1
K 1c
σ b = const
d

100 200 300 400 500
defect size [µm]
Source: Böhler


Developments in tool steel

50 µm 50 µm
µm 50 µm
Melted steel Spray formed steel Powder metal steel
} Inhomogenity } Nearly no segregations } Homogeneous structure
} Segregations } Carbide size < 30 µm } Nearly no segregation
} Carbide size < 200 µm } High-carbide alloy } Carbide size < 3 µm

Processing Processing Processing
} Direct dependency of } Homogeneous structure leads } Problem: hardness and
durability and hardness to better accuracy tenacity at the same time
} Big carbides provoke } More abrasion because of } Cutting edge build-up
breakouts spreaded carbides possible
X155 CrMoV 12 1 mit 62 HRC, different manufacturing processes; Source: Schneider, 2002


Motivation for complete hard milling processes:
The tool manufacturer can “deliver” time

Product development

minimum throughput time

Tool component Tool detail-
development construction

Tool manufacturing
n In this time slot only the tool maker defines the Time-
to-Market!
Design freeze
n During this period only necessary production steps
are allowed which can not be standardized
Stop of changes SOP
n The hard milling process shortens the overall process
and therefore the total lead time


Importance of CAX-processes in tool manufacturing
Material
n Powder metallurgical high-speed
steel S 6-5-3 PM
n Hardness 65 HRC

Demands
n Surface roughness Ra 0,3 µm
n Minimum inner radius 1 mm

Process
n Complete machining
n Simultaneous five-axis-roughing and
-finishing
n Solid carbide and CBN tools
n Complete hydrostatic five-axis-
machine n Complete hard milling process of standardizes
n Process time: roughing 6h, finishing blanks and shortens process chains
5h






5 Conclusion


In the future:
Growing importance of five-axis-processes in tool manufacturing
Development in tool manufacturing
forecast1996
Stand 2007
100 % rate of milling processes

100 % CNC-intersection
3-Axis Roughing/Finishing
75

50 Copy milling

HSC-Finishing
3-Axis
25

5-Axis-HSC
5-Axis
Measuring point/ grid lines 5-Axis

1970 1980 1990 1996 2000 2010


Technology often develops evolutionary – but not always predictable
75% 20 %
60

rate of HSC-milling in
15
45
30 10

manufacturing
15 5
0 0
< declining growing > 04/05 06/07 08/09
Importance of HSC Years

Interview of 2002 Actual development

75% 20 %
60

rate of sink-EDM in
15
45

manufacturing
10
30
15 5

0 0
Importance of sink-EDM Years
Source: Interview of companies (Euromold 2002 and benchmarking database of awf)


Key-turn solutions quickly get into manufacturing
75% 70 %

Availability of potential
60 60
45 50

automation
30 40 2008
15 30 2009
0 2010
20
< declining growing > 10 »Wire »Sink
Importance autom. process chain »Milling«
0 EDM« EDM«

Interview of 2002 Actual development
75% 75%

CAM-programming
60 60
45 45

(milling)
30 30
15 15
0 0
Importance autom. process chain Years
Source: Benchmarking database of awf


Process features of cutting process steps
Roughing (HPC) Pre-finishing Finishing (HSC)
Aim Aim Aim
n maximum metal removal rate Qt n Machining a even stock n maximum metal removal rate
= vf • ae • ap allowance for the finishing step At = vf • ae
Process features Process features Process features
n Mechanical load limit for tools n Critical process status because n High dynamic and thermal
and cutting machine of uneven allowance stress for tool cutting materials
and
n Use of big tool diameters and n Use of ambitious process
resistant cutting materials strategies n Use of small tool diameters and
thermal resistant cutting
n Three-axis machining n Use of different tool diameters
materials
n (Rth = 0,1-0,5 mm) n (Rth = 0,05-0,1 mm)
n Application from Pre-finishing
programs for the finishing with
reconfiguration
n High data volumes of the
NC-programs
n (Rth = 0,002-0,005 mm)


What is HSC?
Engagement conditions
n Finishing process
n Low chip cross section
n High speed (factor 2 bis 10)
n low cutting forces
Work piece
n Very good surface quality for curved areas

Influence of speed:
n High variety of materials, hard materials

Metal removal Machine requirements
n High spindle speed
n High feed rate and acceleration
Surface quality
Tool
Cutting forces n High-performance coating (cutting speed)
Tool life travel path n High temperature resistance of the cutting edge
n Low tool heat influence
speed vc
Source: Schulz; Hochgeschwindigkeitsbearbeitung


Influence of cutting speed on cutting temperatures
vc = 25 m/min JSS 325°C
= v = 75 m/min
c JSS 605°C
= v = 100 m/min
c JSS 655°C
=
20 20 20

µm µm µm

0 0 0

-10 -10 -10
-10 0 µm 20 -10 0 µm 20 -10 0 µm 20
vc = 150 m/min JSS 690°C
= vc = 300 m/min JSS 910°C
= v = 600 m/min
c JSS 1195°C
=
20 20 20

µm µm µm

0 0 0

-10 -10 -10
-10 0 µm 20 -10 0 µm 20 -10 0 µm 20

Material: X180VCrMo951PM (57 HRC) Source: Dissertation Steffen Knodt


Qualitive influence of different process parameters
Definitionen time and costs quality barrier
n Spindle capacity:
Material Tool life surface precision Cutting
P = F * 0.5 * D * n removal time [Lf] [Rz] forces [F]
rate [Q]

n Theoretical roughing depth: Cutting
speed [vc]
n with X: fz or ae
Cutting
depth [ap]
2 2
DT æ DT ö X
Rth = - ç ÷ - Cut width
2 è 2 ø 4 [ae]

Feed rate
per tooth
[fz]
Number of
teeth [Z]


Basic factor: Process control
machined area [cm²]

220
fz= 0,01 mm = const
180

140

100

60
Initial situation
20
coated carbide material

0 50 100 150 200 250 300 350
Cutting speed vc [m/min]

Tool: Torus D3R0,5, CBN; Werkstoff: 1.2343, 55HRC


CBN: Optimum cutting speed is
220
fz= 0,01 mm = const fz= 0,01 mm
180

140

100

60
Initial situation
20
coated carbide material

0 50 100 150 200 250 300 350
Cutting speed vc [m/min]

Tool: Torus D3R0,5, CBN; Werkstoff: 1.2343, 55HRC



Optimum cutting speed is fz= 0,01
220 220
fz= 0,01 mm = const mm
180 selected point 180

140 140

100 100

60 60
Initial situation 20
20
coated carbide material vc= 200 m/min = const

0 50 100 150 200 250 300 350 0,01 0,008 0,006 0,004 0,002 0
Cutting speed vc [m/min] Feed rate per tooth fz [mm]

Tool: Torus D3R0,5, CBN; Material: 1.2343, 55HRC


Machined area [cm²]
Machined area [cm²]

Optimum cutting speed is fz= 0,01
220 220
fz= 0,01 mm = const mm
180 Selected point 180

140 140

100 100

60 60
Initial situation 20
20
coated carbide material vc= 200 m/min = const

0 50 100 150 200 250 300 350 0,01 0,008 0,006 0,004 0,002 0
Cutting speed vc [m/min] Feed rate per tooth fz [mm]

n Studies show: Optimum results can be realized in a very little process window
n Little process changes lead to significant losses in terms of economical efficiency
n To realize complex parts you need to use five-axis motion control to fulfill the demand

Tool: Torus D3R0,5, CBN; Material: 1.2343, 55HRC

Technological core aspects in milling
Milling tools & Coatings Technological orintated Machine & Controling
NC-Programming

Source: Hembrug

n Abrasions-resistance n Harmonic tool path n Precision and repetition
exactness
n Geometrical variety n Stock allowance
n No vibrations
n Precision n Easy and quick operation
n Harmonic motion control
n Stability and process reliability n Implementation of technological
background concerning motion n Low wear
n Technological knowledge
control
n Reliable automation






5 Conclusion


Technological optimized process planning – process modeling
Multi-axial roughing of cavities
0,04 Chip thicknesshsp [mm]

Tool geometrie 0,03
f z(increasing)

n Diameter, twist, 0,02
number of teeth,
n cutting blade geometrie 0,01

Asp hsp 0
Process parameter 110 120 130 140 150 160 170 180
Wrap angle j [°]
n Feed rate per tooth,
cutting speed Fc
WZ- Kont akt - Werkzeug n+1-t e n-t e
Rot at ion zonen- Hüllkurve erzeugt erzeugt 0,03 Chip thicknesshsp [mm]
w inkel Fc Kont ur Kont ur
Werkzeug- a e (increasing)
Track geometrie mit t elpunkt
Zust ellung je 0,02
Kreisbahn ae
n circle, ellipse, spline, …
n track radius, infeed 0,01

n Epizykloids,
hypozykloids 0
Rückw ärt ige Kreisbahn des 100 120 140 160 180
Bew egung Werkzeug-
Wrap angle j [°]
mit t elpunkt es


Technological optimized process planning – Implementation
Roughing of hard materials
A maximum uniformity is given by a minimum Optimal depth of cut for
variation of the cross section. tool diameter = 12mm

Helix angle l [°]

Number of teeth z [-]
15 30 45 60

4 35,2 16,3 9,4 5,4
70,3 32,6 18,8 10,9

28,1 13,1 7,5 4,4
5
56,3 26,1 15,1 8,7
uniformity [-]

23,4 10,9 6,3 3,6
6
46,9 21,8 12,6 7,3

Depending on material L/D relations of
maximum 1,5 – 2 were reached.
As a consequence there are limitations for
the choice of the geometry of the optimal
tool.
Wrap angle [°] ap [mm]


n Tool JH170 Tool life volume [cm³] Material removal rate [cm³/min]
n vc = 90 m/min Tool life volume
n ae = 0,25/ Fc = 30° Material removal rate

The metal removal rate is proportional to the cut depth, but
there is no linear behavior of the cutting volume concerning
cutting depth.


Fxy [N] 240 µm tool flank wear land (VB)
1800
1600
1400 200 * Slot milling
1200
1000 160
800
600 120
400
200
80
fz [mm] 0,06 0,06 0,03 0,03 0,03 0,02
U/ae [°/mm] 30° 10mm 40
vc [m/min] 100 100 60 50 50 20
ap [mm] 10 1 1 3
10 20 30 40 50 60
Material S600 S790 S290 S600 S790 S290
Machined volume [cm³]
V‘ [cm3/min] 1,9 1,9 0,58 1,9 1,9 1,53
JH120 JH120 JH120 JH170
240 µm tool flank wear land (VB)
Tool Jabro Tools Material 1.2379 200 Circular milling
VHM JH120 / *JH170 S 600
Diameter D=10mm S 790 PM
160
Teeth Z=4 S 290 PM 120
80
Slot milling Circular milling U=30° 40
Slot width 10 mm Slot width 13 mm
V‘ = 1,9 cm³/min V‘ = 2 cm³/min
ap = 1 mm ap = 10 mm
10 20 30 40 50 60
Machined volume [cm³]

Further research and Outlook
Process verification on different workpieces
n The circular milling was successfully applied on the complex slot geometries of a Blisk
workpiece made of Ti-6Al-2Sn-4Zr-6Mo (b-processed)
– Large increase of tool life
– Different algorithms for the optimization of the tool paths
– Nearly constant engagement angle of ΦC = 41°






5 Conclusion


Five-Axis-Finishing with torus milling tools:
technological basics
Example for the optimal coordination of angle and lead angle
Zb,a Z
a b degree
1 Contour radius r 24
(simple curved)
50 mm
100 mm
200 mm

Lead angle b
a 500 mm
Yb,a q cos(b) 12
a r
cos(a)
b b z
Xb,a= Xß Yß=Y 6

z
Z
X 0
Aims 0 6 12 degree 24
Y Tool radius RF = 20 mm
n Economic process due to Cutting plate radius rp = 5 mm
Tilt angle a
high axial depth of cut
n High surface quality Theoretical roughness normal to feed rate direction
n Optimum process é æ a ö
2 ù
conditions Rth ,n = reff × sin b × ê1 - 1 - ç e ÷ ú
ê ç 2×r ÷ ú
– Contact length ê
ë è eff ø ú
û
– Cutting speed Source: Zander, Altmüller


Process example
Use of torus mill in the Five-Axis-Finishing
Machining task Conventional Five-axis

n Rotating slider for a injection n Three-Axis-Process with ball-end n Simultaneous Five-Axis-Process
mould mill, ae = 0,1 mm with torus mill, ae = 1 mm
n Surface has to be polished n Process time ca. 120 min n Process time of the surface ca. 25
after process min
n Reached surface quality ca.
n Material: 1.2379, 62 HRC Ra = 1 µm n Reached surface quality ca. Ra =
0,25 µm


Development of process technology for hard milling
Identification of optimum milling parameters for the systematic orientation of coating systems

Motivation
n Complex and challenging material profiles require specific, concrete and
stable process parameters
n Variation of cutting parameters with numeric analysis of cutting to affiliate
mechanic and thermal applied load of the cutting edges and with it abrasion,
impact and temperature resistance

Aim
n Raising of chip thickness Asp(φ) , max. cutting thickness hsp(φ), cutting width
bsp(φ) and reduction of cutting length lsp(k) to reduce abrasive wear
n Necessary condition φ → min

Solution
n Systematic identification of optimum process windows with numeric analysis

n Implementation of analog surveys with identified parameter window
bsp(φ)


Identification of optimum milling parameters for the systematic optimization of coating systems

Hypothesis
n Coatings protect the substrate from thermal but not from mechanical applied
loads
n A minimum applied load on the cutting edges comes along with…
- the most possible cross section area Asp(φ)1, which distributes the normal pressure
1 towards the edge with an even cutting force amplitude and a minimized total load on the
tool while reaching a high productivity due to high material removal rate [3]
2 bsp(φ) - the most possible unformed chip thickness hsp(φ) and width of undeformed chip
thickness bsp(φ), to ensure a high cross section area [2]
- And the smallest possible chip length lsp(k) or wrap angle φ, to reduce the impact time
and therefore minimize the abrasion impact on the cutting edge
3

bsp(φ)

© WZL/Fraunhofer IPT Seite 30

Identification of optimum milling parameters for the systematic orientation of coating systems

Modification of parameters
n Integration of tilt angle Theta (QFB) and Psi (YB) which
become additional degrees of freedom due of the five-axis-
process
n …only with five-axis-process the optimum cutting
parameters can be defined and configured
n Variation of…
- Feed rate per tooth fz = 0,01 … 0.1 [mm]

- Cutting depth ap,n= 0.01 … 0.1 mm

- Axial depth of cut ae,n = 0.01 … 0.1 [mm]

- Theta QFB = 25 … 50 [°]

- Psi YB = 0 … 90 [°]

n Constant Parameters…
bsp(φ)
- Cutting speed vc,eff= 90 [m/min]

- Tool diameter D = 6 [mm]

- Number of teeth z = 2 [-]


Five-axis-process in tool manufacturing
Challenges
n ball end mill tools can machine nearly every component geometry

n Due to ever-changing machining situation is this essential for the
finishing process
Problem
n Different contact conditions in chip formation of three-axis-cutting
with ball mill tool
n »Freedom of geometry« can lead to unfavorable contact conditions
Source:
IPT
in terms of process technology
Solution
n Five-axis-processes allow to influence the process parameters actively,
even with complex geometries
n To use additional degrees of freedom »favorable« and »unfavorable«
process parameters need to be known!


Processexample
Stamp for colt forming operations

10 µm 10 µm

10 µm 10 µm
Quelle: IPT


Process- and CAM development –
Machining example: cold massive forging die
Application
n Cold massive forming: great significance of surface quality for the lifetime
of the tools
n Continuous and fast process chains are demanded

Hart milling processing
n 5-axis machining offers technological advantages
n Optimal availability and stable process management

Objectives
n Transfer and establishment of research results in hard milling in practice
n Exclusively through the use of simultaneously 5-axis hard milling
machining a holistic process stability can be guaranteed.
+ = n Component spectrum
–Complex component geometry
–Bad quality of the CAD-data
n Economic aspects
–Maximum process performance and robust processes
–Optimized component- and clamping devices
–Intuitive CAM- Programming
Source: IPT & ModuleWorks GmbH, Aachen


Hard milling: Net based tool path calculation
»automatic programming: Three axis – five axis «
Programming
n Net-based conversion of 3-axis
tool path into 5-axis path
motion
n Reduction of programming
effort
n Bo support structure is
required
n Less dependent on the CAD
quality

+ =
Quelle: ModuleWorks GmbH, Aachen


Cold massive forming die
Result
n Enhanced surface quality

n Harmonic tool path motion reduces visual
defects caused by the axis
n Ra < 0,15 µm

conventional Net-based

Source:
IPT


Cold massive forming die

n Ra,quer = 0,16 µm

n Ra, längs = 0,12 µm





n Ra,quer = 0,2 µm


Source:
IPT


Geometry adaptive milling tools
Ball end mill
Questions
Flexibility

n What measures can increase the productivity of hard milling processing
Barell tool
significantly?
n How can the required flexibility be retained?

n How is the machining mechanism influenced by the form of the operation
zone?
Productivity
End mill n Maximum adaption of tool geometry for surface properties
Productivity n Use of big line width to reduce the required process time

n Large ration of rv/rh, for end mill rh/rv à ¥

Geometric flexibility
n Use of milling tools with „universal“ geometry

n Low ratio of rv/rh, for ball head milling cutter rv/rh à 1
rh

rv source: IPT


Geometry adaptive milling tools

Milling tool technology: geometric flexibility vs. productivity
1 Ball end mill 1 Ball end mill
Flexibility

§ Maximum flexibility and least productivity
Barrel tool
§ Fast programming due to simple geometry

2 2 Geometry adaptive milling tool ››barrel tool‹‹
§ High process flexibility while simultaneously high productivity
§ Production of complex free form surfaces and ruled
geometries
3 3 Torus-/End mill
workpiece Torus § High productivity with severely limited flexibility
§ Only simple curved surfaces can be machined Source:
Productivity IPT

Solution - combining both characteristics of
ball end mill and end mill






5 Conclusion


End of the journey?
Hard milling
Summary
n Due to simultaneous 5-axis processes - reduction of critical time-to-
market lead times
n Utilization of latest machine equipment and milling tools for the
optimization of the holistic process performance
n Further simplification of the CAM-programming

n Addressing the correct process windows and ensuring constant processes
is essential for the further introduction of simultaneous 5-axis processes
Outlook
n Further implementation tool contact situations and process forces into the
tool motion planning
n Optimized process planning via CAM integrated simulation and
Source: IPT & ModuleWorks GmbH, Aachen implementation of specific process knowledge


Your contact to Fraunhofer IPT
Dipl.-Ing. Benedikt Gellissen

Fraunhofer Institute for Production Technology IPT
Steinbachstraße 17, 52074 Aachen
Phone: +49 241 89 04-256
Fax: +49 241 89 04-6256
Mail: benedikt.gellissen@ipt.fraunhofer.de


:


Palestra 4 - Avanços em tecnologia de fresamento: do fresamento convencional para o HSC.

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Palestra 4 - Avanços em tecnologia de fresamento: do fresamento convencional para o HSC.