textured cutting tools
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Performance of electrical discharge textured cutting tools
P. Koshy, J. ToveyMcMaster University
Canada
2/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Lubrication in cutting
Infiltration of lubricant is controlled by capillary action and chip velocity-induced shear flowRetention of the lubricant in the interface is as critical as its ingressLubrication may be enhanced through texturing the tool rake face surface
sticking
slidingtool
chip
tool
chiptool
chip
lubricant
3/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Femtosecond laser texturing
Enomoto & Sugihara (2010)
Texture is to be preferably oriented normal to the chip flow direction
Kawasegi et al (2009)
micro nano
4/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Electrochemical texturing
anode (workpiece)
metal layer(cathode)
insulation layer
Zhu et al (2009)
dimpled texture
5/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Electrical discharge texturing
Surfaces generated in electrical discharge machining (EDM) are isotropic and entail a positive skewness, which predisposes them towards effectively entraining lubricant
surface height
frequency
+ve skew
6/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Objective of this work
To prove the concept of ED-textured cutting toolsIdentify the envelope of EDM and cutting parameters in which such textures are effective
areal texture machinedwith a block electrode
cutting edge
linear texture machinedwith shim stock tooling
rake face
7/18
Experimental - EDM
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
copper electrodes with positive polarityoil based dielectricaverage gap voltage 100 V; duty factor 50%Pulse current <72 A; pulse on-time <133 µs
Pulse current and on-time were varied to alter the geometry of the characteristic crater
8/18
Experimental - Cutting
continuous & intermittent orthogonal cuttingAISI T-15 High Speed Steel ground insertsSPG 432 geometry with 0° rake angleannealed 1045 steel & 6061 Al workpiecescutting speed 2−75 m/min; feed 0.025−0.1 mm cutting width 3 mm; oil lubricant
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
toolchip
Fc
Ff
friction angle
In comparison to surface roughness and tool life, machining force is a better indicator of lubrication effectiveness, in terms of repeatability and resolution
De Chiffre & Belluco (2000)
9/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Texture parameters
Texture depth was limited to prevent the tool from functioning as a restricted rake tool
relief on the rake face to restrict tool chip contact
restricted rake tool
de
Distance de is to be optimized with respect to the uncut chip thicknessMaximum force reduction referred to the texture with a roughness of 12 µm Ra, generated at a current of 39 A and an on-time of 42 µs Texturing time is ~10 seconds
10/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Effectiveness of ED-texture
0 30 60 90 120 150 18016
20
24
28
32
Time (s)
ground tool
Fric
tion
angl
e (°
)
lubricant application
0 30 60 90 120 150 18016
20
24
28
32
Fric
tion
angl
e (°
)
Time (s)
textured tool
11/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Force reduction in continuous cutting
0
1.5
3.0
4.5
6.0
Feed
forc
e (x
102 N
)
non-
text
ured
text
ured
0
2
4
6
8
10
12
Cut
ting
forc
e (x
102 N
)
text
ured
non-
text
ured
Texturing decreases the forces and the variability, with the effect more pronounced in the feed direction
12/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Force reduction in intermittent cutting
0 1 2 3 4 5
0
1
2
3
4
5
6
Feed
forc
e (x
102 N
)
Time (s)0 1 2 3 4 5
0
2
4
6
8
10
12
Cut
ting
forc
e (x
102 N
)Time (s)
textured
non-textured
Feed force reduction is higher in intermittent cutting as the lubricant is directly replenished on the tool rake face during the non-cutting interval
13/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Effect of cutting parameters on force reduction
0 5 10 15 20 25
0
10
20
30
40
50
Cutting speed (m/min)
continuous
intermittent
Cutting speed (m/min)
50 µm
0 15 30 45 60 75 90
0
5
10
15
20
25
30%
redu
ctio
n in
feed
forc
e
25 µm feed
Texturing is more effective at the low end of typical cutting speeds, at fine feeds and in intermittent cutting
14/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Force reduction in cutting of aluminum
0 5 10 15 20 250.0
0.5
1.0
1.5
2.0
2.5
Feed
forc
e (x
102 N
)
Time (s)0 5 10 15 20 25
0
1
2
3
4
5
Cut
ting
forc
e (x
102 N
)
Time (s)
non-texturedtextured
Forces and the associated variability were significantly lower as the lubricant used was specifically formulated for cutting aluminum
15/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Effect of texture location
0 3 6 9 12 15 18
18
20
22
24
26
Fric
tion
angl
e (°
)
(de/h)
h = 25 µm100 µm 50 µm
toolchip
h
Force reduction is maximized when (de/h) is ~2−3As the tool chip contact length is typically 4−6 times the feed h, this implies that texturing needs to correspond to just the sliding region
de
16/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Comparison of linear and areal textures
linear Textured area was varied by altering the pitch in the linear texture
0 20 40 60 80 10005
1015202530
% re
duct
ion
in fo
rce
% area textured
feed force
cutting forceareal
Results confirm that the areal texture is to be preferred over a linear one
17/18
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Role of texture parameters on force reduction
Force reduction showed no systematic trends with respect to either the Ra roughness or the pulse parameters
1.5 2.0 2.5 3.0 3.5 4.0
05
101520253035
KurtosisSkewness0.0 0.2 0.4 0.6
05
101520253035
% re
duct
ion
in fo
rce feed force
cutting force
Force reduction exhibited defined maxima with respect to skewness and kurtosis of the texture
18/18
Electrical discharge texturing has been demonstrated to bring about a significant (15−40%) reduction in machining force through enhanced lubrication at the tool-chip interfaceThe skewness and kurtosis of the texture are good indicators of the extent of force reductionThe concept is attractive for application in broaches, taps, gear cutting tools and possibly forming toolsMechanical imprinting of said texture during the compaction phase of tool inserts (as opposed to EDM of inserts) may be explored
Conclusions
Performance of electrical discharge textured cutting toolsP. Koshy, J. Tovey
61st CIRP General AssemblyBudapest, August 24, 2011
Thank you for your kind attention!
Canadian Network of Centers of Excellence
Natural Sciences & Engineering Research Council of Canada
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