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Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey McMaster University Canada.

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Presentation on theme: "Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey McMaster University Canada."— Presentation transcript:

1 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey McMaster University Canada

2 2/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Lubrication in cutting Infiltration of lubricant is controlled by capillary action and chip velocity-induced shear flow Retention of the lubricant in the interface is as critical as its ingress Lubrication may be enhanced through texturing the tool rake face surface sticking sliding tool chip tool chip tool chip lubricant

3 3/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, 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) micronano

4 4/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Electrochemical texturing anode (workpiece) metal layer (cathode) insulation layer Zhu et al (2009) dimpled texture

5 5/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, 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 6/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Objective of this work To prove the concept of ED-textured cutting tools Identify the envelope of EDM and cutting parameters in which such textures are effective areal texture machined with a block electrode cutting edge linear texture machined with shim stock tooling rake face

7 7/18 Experimental - EDM Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 copper electrodes with positive polarity oil based dielectric average 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 8/18 Experimental - Cutting continuous & intermittent orthogonal cutting AISI T-15 High Speed Steel ground inserts SPG 432 geometry with 0° rake angle annealed 1045 steel & 6061 Al workpieces cutting speed 2−75 m/min; feed 0.025−0.1 mm cutting width 3 mm; oil lubricant Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 tool chip FcFc FfFf 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 9/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, 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 d e Distance d e is to be optimized with respect to the uncut chip thickness Maximum 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 10/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Effectiveness of ED-texture 0306090120150180 16 20 24 28 32 Time (s) ground tool Friction angle (°) lubricant application 0306090120150180 16 20 24 28 32 Friction angle (°) Time (s) textured tool

11 11/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Force reduction in continuous cutting 0 1.5 3.0 4.5 6.0 Feed force (x10 2 N) non-textured textured 0 2 4 6 8 10 12 Cutting force (x10 2 N) textured non-textured Texturing decreases the forces and the variability, with the effect more pronounced in the feed direction

12 12/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Force reduction in intermittent cutting 012345 0 1 2 3 4 5 6 Feed force (x10 2 N) Time (s) 012345 0 2 4 6 8 10 12 Cutting force (x10 2 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 13/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Effect of cutting parameters on force reduction 0510152025 0 10 20 30 40 50 Cutting speed (m/min) continuous intermittent Cutting speed (m/min) 50 µm 0153045607590 0 5 10 15 20 25 30 % reduction in feed force 25 µm feed Texturing is more effective at the low end of typical cutting speeds, at fine feeds and in intermittent cutting

14 14/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Force reduction in cutting of aluminum 0510152025 0.0 0.5 1.0 1.5 2.0 2.5 Feed force (x10 2 N) Time (s) 0510152025 0 1 2 3 4 5 Cutting force (x10 2 N) Time (s) non-textured textured Forces and the associated variability were significantly lower as the lubricant used was specifically formulated for cutting aluminum

15 15/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Effect of texture location 0369121518 20 22 24 26 Friction angle (°) (de/h)(de/h) h = 25 µm 100 µm 50 µm tool chip h Force reduction is maximized when (d e /h) is ~2−3 As 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 d e

16 16/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011 Comparison of linear and areal textures linear Textured area was varied by altering the pitch in the linear texture 020406080100 0 5 10 15 20 25 30 % reduction in force % area textured feed force cutting force areal Results confirm that the areal texture is to be preferred over a linear one

17 17/18 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, 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 1.52.02.53.03.54.0 0 5 10 15 20 25 30 35 KurtosisSkewness 0.00.20.40.6 0 5 10 15 20 25 30 35 % reduction in force feed force cutting force Force reduction exhibited defined maxima with respect to skewness and kurtosis of the texture

18 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 interface The skewness and kurtosis of the texture are good indicators of the extent of force reduction The concept is attractive for application in broaches, taps, gear cutting tools and possibly forming tools Mechanical 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 tools P. Koshy, J. Tovey 61 st CIRP General Assembly Budapest, August 24, 2011

19 Thank you for your kind attention! Canadian Network of Centers of Excellence Natural Sciences & Engineering Research Council of Canada


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