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Performance of electrical discharge textured cutting tools

Performance of electrical discharge textured cutting tools. P . Koshy, J. Tovey. McMaster University Canada. chip. chip. tool. sliding. tool. chip. sticking. tool. Lubrication in cutting. Infiltration of lubricant is controlled by capillary action and chip velocity-induced shear flow

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Performance of electrical discharge textured cutting tools

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

  2. chip chip tool sliding tool chip sticking tool • 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 lubricant Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  3. Femtosecond laser texturing • Texture is to be preferably oriented normal to the chip flow direction Enomoto & Sugihara (2010) micro nano Kawasegi et al (2009) Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

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

  5. Electrical discharge texturing • Surfaces generated in electrical discharge machining (EDM) are isotropic and entail a positive skewness, which predisposes them towards effectively entraining lubricant frequency surface height +ve skew Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  6. 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 rake face linear texture machined with shim stock tooling cutting edge areal texture machined with a block electrode Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  7. Experimental - EDM • Pulse current and on-time were varied to alter the geometry of the characteristic crater Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  8. chip tool Fc Ff friction angle Experimental - Cutting • 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) Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  9. Texture parameters • Texture depth was limited to prevent the tool from functioning as a restricted rake tool • Distance de is to be optimized with respect to the uncut chip thickness relief on the rake face to restricttool chip contact • 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 d e restricted rake tool Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  10. Effectiveness of ED-texture lubricant application ground tool textured tool 32 32 28 28 Friction angle (°) 24 24 Friction angle (°) 20 20 16 16 0 30 60 90 120 150 180 0 30 60 90 120 150 180 Time (s) Time (s) Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  11. Force reduction in continuous cutting • Texturing decreases the forces and the variability, with the effect more pronounced in the feed direction 12 6.0 10 4.5 8 Cutting force (x102 N) 6 Feed force (x102 N) 3.0 4 non-textured textured 1.5 non-textured 2 textured 0 0 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  12. Force reduction in intermittent cutting 6 12 non-textured 10 5 8 4 Cutting force (x102 N) 6 Feed force (x102 N) 3 4 2 2 1 textured 0 0 0 1 2 3 4 5 0 1 2 3 4 5 Time (s) Time (s) • Feed force reduction is higher in intermittent cutting as the lubricant is directly replenished on the tool rake face during the non-cutting interval Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  13. Effect of cutting parameters on force reduction 30 50 intermittent 25 40 20 30 25 µm feed 15 % reduction in feed force 20 10 continuous 10 5 50 µm 0 0 0 15 30 45 60 75 90 0 5 10 15 20 25 Cutting speed (m/min) Cutting speed (m/min) • Texturing is more effective at the low end of typical cutting speeds, at fine feeds and in intermittent cutting Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  14. Force reduction in cutting of aluminum 2.5 5 2.0 4 1.5 3 Cutting force (x102 N) Feed force (x102 N) 1.0 2 non-textured textured 0.5 1 0.0 0 0 5 10 15 20 25 0 5 10 15 20 25 • Forces and the associated variability were significantly lower as the lubricant used was specifically formulated for cutting aluminum Time (s) Time (s) Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  15. chip tool • Effect of texture location 26 24 h = 25 µm 100 µm 50 µm 22 Friction angle (°) h 20 18 0 3 6 9 12 15 18 d • Force reduction is maximized when (de/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 (de/h) e Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  16. Comparison of linear and areal textures 30 areal 25 feed force 20 % reduction in force 15 cutting force 10 5 0 0 20 40 60 80 100 • Textured area was varied by altering the pitch in the linear texture linear % area textured • Results confirm that the areal texture is to be preferred over a linear one Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  17. Role of texture parameters on force reduction 35 35 feed force 30 30 25 25 20 20 cutting force % reduction in force 15 15 10 10 5 5 0 0 0.0 0.2 0.4 0.6 1.5 2.0 2.5 3.0 3.5 4.0 Skewness Kurtosis • Force reduction showed no systematic trends with respect to either the Ra roughness or the pulse parameters • Force reduction exhibited defined maxima with respect to skewness and kurtosis of the texture Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

  18. Conclusions • 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 Performance of electrical discharge textured cutting tools P. Koshy, J. Tovey 61st CIRP General Assembly Budapest, August 24, 2011

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

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