palestra 4 - avanços em tecnologia de fresamento: do fresamento convencional para o hsc
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Advances in milling Technologies: from convencional milling to HSC. Palestrante: Msc. Benedikt Gellissen - Instituto Fraunhofer de Tecnologias da Produção - FhG IPT - AlemanhaTRANSCRIPT
© WZL/Fraunhofer IPT
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
Page 1© WZL/Fraunhofer IPT
Outline of the presentation
What is the motivation for advanced milling technologies1
What is required to realize a successfull implementation of HSC?2
Advanced roughing possibilities3
Improved finishing results due to intelligent CAM-Systems and tool adaption4
Conclusion5
Page 2© WZL/Fraunhofer IPT
Importance of the milling technology for the molding industry -Comparability of tool types and use of technology
Injection moulding
Special featuresn Surfacen Precisionn Filigree
Solid forging
Special featuresn Material (Temperature)n Edge zonen Precision
Deep drawing
Special featuresn Surfacen Precisionn Geometrie
Stamping and bending
Special featuresn Materialn Precisionn Surface
Focus free-form surfacesPrismatic toolcomponents
Importance
Milling
Turning
Grinding
Sink EDM
Wire EDM
Process
Importance
Milling
Turning
Grinding
Sink EDM
Wire EDM
Importance
Milling
Turning
Grinding
Sink EDM
Wire EDM
Importance
Milling
Turning
Grinding
Sink EDM
Wire EDM
Process Process Process
Page 3© WZL/Fraunhofer IPT
Driver »tool steel«: Improved materials for the industryImpact of the defect size on the bending resistance
Source: Böhler
4
3
2
1
100 200 300 400 500
d
Kconst σ 1c
b =
powder metallurgical
conventional forging
conventional founded
σb[kN/mm2]
defect size [µm]
bend
ing
resi
sten
ceAims
n Reaching an homogeneous structure
n Low corn and carbide size for improved wear resistance and strength
n Reduction of material anisotropy in case of manufacturing
Page 4© WZL/Fraunhofer IPT
Melted steel } Inhomogenity} Segregations} Carbide size < 200 µm
Processing} Direct dependency of
durability and hardness} Big carbides provoke
breakouts
50 µm
Developments in tool steel
50 µm
Powder metal steel} Homogeneous structure} Nearly no segregation} Carbide size < 3 µm
Processing} Problem: hardness and
tenacity at the same time} Cutting edge build-up
possible
Spray formed steel} Nearly no segregations} Carbide size < 30 µm} High-carbide alloy
Processing} Homogeneous structure leads
to better accuracy} More abrasion because of
spreaded carbides
50 µm50 µm
X155 CrMoV 12 1 mit 62 HRC, different manufacturing processes; Source: Schneider, 2002
Page 5© WZL/Fraunhofer IPT
Motivation for complete hard milling processes:The tool manufacturer can “deliver” time
minimum throughput time
Tool componentdevelopment
Tool manufacturing
SOP
Product development
n In this time slot only the tool maker defines the Time-to-Market!
n During this period only necessary production steps are allowed which can not be standardized
n The hard milling process shortens the overall process and therefore the total lead time
Design freeze
Stop of changes
Tool detail-construction
Page 6© WZL/Fraunhofer IPT
Material
n Powder metallurgical high-speed steel S 6-5-3 PM
n Hardness 65 HRC
Demands
n Surface roughness Ra 0,3 µmn Minimum inner radius 1 mm
Process
n Complete machiningn Simultaneous five-axis-roughing and
-finishingn Solid carbide and CBN toolsn Complete hydrostatic five-axis-
machinen Process time: roughing 6h, finishing
5h
n Complete hard milling process of standardizes blanks and shortens process chains
Importance of CAX-processes in tool manufacturing
Page 7© WZL/Fraunhofer IPT
Outline of the presentation
What is the motivation for advanced milling technologies1
What is required to realize a successfull implementation of HSC?2
Advanced roughing possibilities3
Improved finishing results due to intelligent CAM-Systems and tool adaption4
Conclusion5
Page 8© WZL/Fraunhofer IPT
In the future: Growing importance of five-axis-processes in tool manufacturing
Development in tool manufacturing
100 % rate of milling processes
75
50
25
2000199019801970 1996
Copy milling
Measuring point/ grid lines 5-Axis 5-Axis
100
% C
NC
-inte
rsec
tion
HSC-Finishing3-Axis
3-Axis Roughing/Finishing
5-Axis-HSC
2010
Stand 1996forecast 2007
Page 9© WZL/Fraunhofer IPT
Importance of HSC<< declining growing >
0
15
30
45
60
75%
Technology often develops evolutionary – but not always predictable
Actual developmentInterview of 2002
0
5
10
15
20 %
rate
of H
SC
-mill
ing
in
man
ufac
turin
g
Years04/05 06/07 08/09
Importance of sink-EDM< declining growing >
0
15
30
45
60
75%
0
5
10
15
20 %
rate
of s
ink-
ED
M in
man
ufac
turin
g
Years04/05 06/07 08/09
Source: Interview of companies (Euromold 2002 and benchmarking database of awf)
Page 10© WZL/Fraunhofer IPT
Key-turn solutions quickly get into manufacturing
Source: Benchmarking database of awf
0
10
20
30
40
50
60
70 %
Ava
ilabi
lity
of p
oten
tial
auto
mat
ion
200820092010
»Milling«»Sink EDM«
»WireEDM«
< declining growing >Importance autom. process chain
0
15
30
45
60
75%
< declining growing >Importance autom. process chain
0
15
30
45
60
75%
CA
M-p
rogr
amm
ing
(mill
ing)
01530456075%
Years04/05 06/07 08/09
Actual development Interview of 2002
Page 11© WZL/Fraunhofer IPT
Process features of cutting process steps
Roughing (HPC)
Aim
n maximum metal removal rate Qt = vf • ae • ap
Process features
n Mechanical load limit for tools and cutting machine
n Use of big tool diameters and resistant cutting materials
n Three-axis machining
n (Rth = 0,1-0,5 mm)
Pre-finishing
Aim
n Machining a even stock allowance for the finishing step
Process features
n Critical process status because of uneven allowance
n Use of ambitious process strategies
n Use of different tool diameters
n (Rth = 0,05-0,1 mm)
Finishing (HSC)
Aim
n maximum metal removal rate At = vf • ae
Process features
n High dynamic and thermal stress for tool cutting materials and
n Use of small tool diameters and thermal resistant cutting materials
n Application from Pre-finishing programs for the finishing with reconfiguration
n High data volumes of theNC-programs
n (Rth = 0,002-0,005 mm)
Page 12© WZL/Fraunhofer IPT
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
n High variety of materials, hard materials
Machine requirements
n High spindle speed
n High feed rate and acceleration
Tool
n High-performance coating (cutting speed)
n High temperature resistance of the cutting edge
n Low tool heat influencespeed vc
Tool life travel path
Cutting forces
Surface quality
Metal removal
Influence of speed:
Source: Schulz; Hochgeschwindigkeitsbearbeitung
Page 13© WZL/Fraunhofer IPT
Influence of cutting speed on cutting temperaturesvc = 25 m/min JSS= 325°C
-10 0 20
-10
0
20
µm
µmvc= 150 m/min JSS= 690°C
-10 0 20
-10
0
20
µm
µm
vc = 300 m/min JSS= 910°C
-10 0 20
-10
0
20
µm
µm
vc = 600 m/min JSS= 1195°C
-10 0 20
-10
0
20
µm
µm
vc = 100 m/min JSS= 655°C
-10 0 20
-10
0
20
µm
µm
vc = 75 m/min JSS= 605°C
-10 0 20
-10
0
20
µm
µm
Material: X180VCrMo951PM (57 HRC) Source: Dissertation Steffen Knodt
Page 14© WZL/Fraunhofer IPT
Qualitive influence of different process parameters
time and costs quality barrier
Material removal rate [Q]
Tool life time [Lf]
surface [Rz]
precision Cutting forces [F]
Cutting speed [vc]
Cutting depth [ap]
Cut width [ae]
Feed rate per tooth [fz]
Number of teeth [Z]
4
X
2D
2D
R22
TTth -÷
øö
çèæ-=
Definitionen
n Spindle capacity:P = F * 0.5 * D * n
n Theoretical roughing depth:
n with X: fz or ae
Page 15© WZL/Fraunhofer IPT
Basic factor: Process control
300
20
100
140
180
0 50 100 150 200 250
Cutting speed vc [m/min]
60
350
220
mac
hin
ed a
rea
[cm
²]
Initial situation
coated carbide material
fz= 0,01 mm = const
Tool: Torus D3R0,5, CBN; Werkstoff: 1.2343, 55HRC
Page 16© WZL/Fraunhofer IPT
Basic factor: Process control
300
20
100
140
180
0 50 100 150 200 250
Cutting speed vc [m/min]
60
350
220
mac
hin
ed a
rea
[cm
²]
Initial situation
coated carbide material
fz= 0,01 mm = const
Tool: Torus D3R0,5, CBN; Werkstoff: 1.2343, 55HRC
CBN: Optimum cutting speed is fz= 0,01 mm
Page 17© WZL/Fraunhofer IPT
Basic factor: Process control
300
20
100
140
180
0 50 100 150 200 250
Cutting speed vc [m/min]
60
350
220
mac
hin
ed a
rea
[cm
²]
Initial situation
coated carbide material
20
100
140
180
0,01 0,008 0,006 0,004 0,002
Feed rate per tooth fz [mm]
60
220
mac
hin
ed a
rea
[cm
²]
0
selected point
vc= 200 m/min = const
fz= 0,01 mm = const
Tool: Torus D3R0,5, CBN; Material: 1.2343, 55HRC
Optimum cutting speed is fz= 0,01 mm
Page 18© WZL/Fraunhofer IPT
Basic factor: Process control
300
20
100
140
180
0 50 100 150 200 250
Cutting speed vc [m/min]
60
350
220
Mac
hin
ed a
rea
[cm
²]
Initial situation
coated carbide material
20
100
140
180
0,01 0,008 0,006 0,004 0,002
Feed rate per tooth fz [mm]
60
220
Mac
hin
ed a
rea
[cm
²]
0
Selected point
vc= 200 m/min = const
fz= 0,01 mm = const
Tool: Torus D3R0,5, CBN; Material: 1.2343, 55HRC
Optimum cutting speed is fz= 0,01 mm
n Studies show: Optimum results can be realized in a very little process windown Little process changes lead to significant losses in terms of economical efficiencyn To realize complex parts you need to use five-axis motion control to fulfill the demand
Page 19© WZL/Fraunhofer IPT
Technological core aspects in milling
Milling tools & Coatings Technological orintated NC-Programming
Machine & Controling
n Abrasions-resistance
n Geometrical variety
n Precision
n Stability and process reliability
n Technological knowledge
n Harmonic tool path
n Stock allowance
n Easy and quick operation
n Implementation of technological background concerning motion control
n Precision and repetition exactness
n No vibrations
n Harmonic motion control
n Low wear
n Reliable automation
Source: Hembrug
Page 20© WZL/Fraunhofer IPT
Outline of the presentation
What is the motivation for advanced milling technologies1
What is required to realize a successfull implementation of HSC?2
Advanced roughing possibilities3
Improved finishing results due to intelligent CAM-Systems and tool adaption4
Conclusion5
Page 21© WZL/Fraunhofer IPT
Technological optimized process planning – process modeling Multi-axial roughing of cavities
Track geometrie
n circle, ellipse, spline, …n track radius, infeedn Epizykloids,
hypozykloids
Tool geometrie
n Diameter, twist, number of teeth,
n cutting blade geometrie
Process parameter
n Feed rate per tooth, cutting speed
hsp
WZ-Rotat ion
Zustellung je Kreisbahn ae
WerkzeugHüllkurve
Werkzeug-mit telpunkt
n-teerzeugt Kontur
n+1-teerzeugt Kontur
Kontakt-zonen-winkel Fc
Rückwärt igeBewegung
Kreisbahn desWerkzeug-mit telpunktes
WZ-Rotat ion
Zustellung je Kreisbahn ae
WerkzeugHüllkurve
Werkzeug-mit telpunkt
n-teerzeugt Kontur
n+1-teerzeugt Kontur
Kontakt-zonen-winkel Fc
Rückwärt igeBewegung
Kreisbahn desWerkzeug-mit telpunktes
Fc
Asp 0
0,01
0,02
0,03
0,04 Chip thickness hsp [mm]
Wrap angle j [°]110 120 130 140 150 160 170 180
fz(increasing)
0
0,01
0,02
0,03 Chip thickness hsp [mm]
ae
Wrap angle j [°]100 120 140 160 180
(increasing)
Page 22© WZL/Fraunhofer IPT
Technological optimized process planning – ImplementationRoughing of hard materials
A maximum uniformity is given by a minimum variation of the cross section.
Wrap angle [°] ap [mm]
unifo
rmity
[-]
Helix angle l [°]
4
5
6
35,2
28,1
23,4
15
70,3
56,3
46,9
30
16,332,6
13,126,1
10,921,8
45
9,418,8
7,515,1
6,312,6
60
5,410,9
4,48,7
3,67,3N
um
ber
of
teet
h z
[-]
Optimal depth of cut fortool diameter = 12mm
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.
Page 23© WZL/Fraunhofer IPT
Technological optimized process planning – ImplementationRoughing of hard materialsn Tool JH170
n vc = 90 m/min
n ae = 0,25/ Fc = 30°
The metal removal rate is proportional to the cut depth, but there is no linear behavior of the cutting volume concerning cutting depth.
Tool life volume [cm³]
Tool life volume
Material removal rate
Material removal rate [cm³/min]
Page 24© WZL/Fraunhofer IPT
Technological optimized process planning – Implementation Roughing of hard materials
Tool Jabro Tools VHM JH120 / *JH170Diameter D=10mmTeeth Z=4
Slot millingSlot width 10 mmV‘ = 1,9 cm³/minap = 1 mm
Circular milling U=30°Slot width 13 mmV‘ = 2 cm³/minap = 10 mm
Material 1.2379S 600S 790 PMS 290 PM
40
80
120
160
200
240 µm tool flank wear land (VB)
10 20 30 40 50 60Machined volume [cm³]
Slot milling
40
80
120
160
200
240 µm tool flank wear land (VB)
10 20 30 40 50 60Machined volume [cm³]
Circular milling
*
200400600800
10001200140016001800
Fxy [N]
U/ae [°/mm]vc [m/min]
fz [mm]
V‘ [cm3/min] 1,9 0,58
ap [mm]
Material S600 S290
1,9
10030°
10
0,03
S790
60100
0,060,06
S600 S290S790
0,03 0,03 0,02
JH170JH120JH120
20311
50 50
JH1201,9 1,9 1,53
10mm
Page 25© WZL/Fraunhofer IPT
Further research and OutlookProcess 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°
Page 26© WZL/Fraunhofer IPT
Outline of the presentation
What is the motivation for advanced milling technologies1
What is required to realize a successfull implementation of HSC?2
Advanced roughing possibilities3
Improved finishing results due to intelligent CAM-Systems and tool adaption4
Conclusion5
Page 27© WZL/Fraunhofer IPT
Five-Axis-Finishing with torus milling tools:technological basics
Aimsn Economic process due to
high axial depth of cutn High surface qualityn Optimum process
conditions– Contact length– Cutting speed
a
a bZZb,a
Xb,a= Xß
Yb,a
bYß=Y
Source: Zander, Altmüller
Example for the optimal coordination of angle and lead angle
Tool radius RF = 20 mmCutting plate radius rp = 5 mm
Tilt angle a
Lead
ang
le b
24degree
12
6
012 degree6 240
Contour radius r (simple curved)
50 mm100 mm200 mm500 mm
z
a cos(b)
XZ
Y
cos(a)
q
b
z
1
r
úúú
û
ù
êêê
ë
é
÷÷ø
öççè
æ
×--××=
2
, 211sin
eff
eeffnth r
arR b
Theoretical roughness normal to feed rate direction
Page 28© WZL/Fraunhofer IPT
Process exampleUse of torus mill in the Five-Axis-Finishing
Conventional Five-axis
n Three-Axis-Process with ball-end mill, ae = 0,1 mm
n Process time ca. 120 min
n Reached surface quality ca. Ra = 1 µm
n Simultaneous Five-Axis-Process with torus mill, ae = 1 mm
n Process time of the surface ca. 25 min
n Reached surface quality ca. Ra = 0,25 µm
Machining task
n Rotating slider for a injection mould
n Surface has to be polished after process
n Material: 1.2379, 62 HRC
Page 29© WZL/Fraunhofer IPT
Development of process technology for hard millingIdentification 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 windowbsp(φ)
Seite 30© WZL/Fraunhofer IPT© WZL/Fraunhofer IPT
bsp(φ)
1
2
bsp(φ)
3
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 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]
- 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
Development of process technology for hard millingIdentification of optimum milling parameters for the systematic optimization of coating systems
Page 31© WZL/Fraunhofer IPT
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…
- Cutting speed vc,eff= 90 [m/min]
- Tool diameter D = 6 [mm]
- Number of teeth z = 2 [-]
bsp(φ)
Development of process technology for hard millingIdentification of optimum milling parameters for the systematic orientation of coating systems
Page 32© WZL/Fraunhofer IPT
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 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!
Source: IPT
Five-axis-process in tool manufacturing
Page 33© WZL/Fraunhofer IPT
10 µm
10 µm 10 µm
10 µm
ProcessexampleStamp for colt forming operations
Quelle: IPT
Page 34© WZL/Fraunhofer IPT
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
Process- and CAM development –Machining example: cold massive forging die
+ =
Source: IPT & ModuleWorks GmbH, Aachen
Page 35© WZL/Fraunhofer IPT
Hard milling: Net based tool path calculation»automatic programming: Three axis – five axis «
Programmingn 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
Page 36© WZL/Fraunhofer IPT
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
Hard milling: Net based tool path calculationCold massive forming die
Source: IPT
Page 37© WZL/Fraunhofer IPT
Hard milling: Net based tool path calculationCold massive forming die
n Ra,quer = 0,16 µm
n Ra, längs = 0,12 µm
n Ra,quer = 0,25 µm
n Ra, längs = 0,25 µm
n Ra,quer = 0,14 µm
n Ra, längs = 0,07 µm
n Ra,quer = 0,2 µm
n Ra, längs = 0,15 µm
Source: IPT
Page 38© WZL/Fraunhofer IPT
Questions
n What measures can increase the productivity of hard milling processing significantly?
n How can the required flexibility be retained?
n How is the machining mechanism influenced by the form of the operation zone?
Productivity
n Maximum adaption of tool geometry for surface properties
n Use of big line width to reduce the required process time
n Large ration of rv/rh, for end mill rh/rvà ¥
Geometric flexibility
n Use of milling tools with „universal“ geometry
n Low ratio of rv/rh, for ball head milling cutter rv/rhà 1
source: IPT
Fle
xib
ility
Productivity
Barell tool
End mill
Ball end mill
rv
rh
Geometry adaptive milling tools
Page 39© WZL/Fraunhofer IPT
Solution - combining both characteristics ofball end mill and end mill
Geometry adaptive milling tool ››barrel tool‹‹
§High process flexibility while simultaneously high productivity
§Production of complex free form surfaces and ruled geometries
1
2
3 Torus-/End mill
§High productivity with severely limited flexibility
§Only simple curved surfaces can be machined
Ball end mill
§Maximum flexibility and least productivity
§Fast programming due to simple geometry
Milling tool technology: geometric flexibility vs. productivity
Fle
xib
ility
Productivity
Barrel tool
Torus
Ball end mill1
2
3
workpiece
Source: IPT
Geometry adaptive milling tools
Page 40© WZL/Fraunhofer IPT
Outline of the presentation
What is the motivation for advanced milling technologies1
What is required to realize a successfull implementation of HSC?2
Advanced roughing possibilities3
Improved finishing results due to intelligent CAM-Systems and tool adaption4
Conclusion5
Page 41© WZL/Fraunhofer IPT
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 implementation of specific process knowledge
End of the journey?Hard milling
Source: IPT & ModuleWorks GmbH, Aachen
Page 42© WZL/Fraunhofer IPT
Your contact to Fraunhofer IPT
Dipl.-Ing. Benedikt Gellissen
Fraunhofer Institute for Production Technology IPTSteinbachstraße 17, 52074 AachenPhone: +49 241 89 04-256Fax: +49 241 89 04-6256Mail: [email protected]
Page 43© WZL/Fraunhofer IPT
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