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N. Z. Yussefian, P. Koshy McMaster University, Canada S. Buchholz, F. Klocke

Electro-erosion edge honing of cutting tools. N. Z. Yussefian, P. Koshy McMaster University, Canada S. Buchholz, F. Klocke RWTH Aachen University, Germany. Edge preparation of cutting tools. hone. chamfer. ~ µm. Influences chip formation Affects surface integrity

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N. Z. Yussefian, P. Koshy McMaster University, Canada S. Buchholz, F. Klocke

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  1. Electro-erosion edge honing of cutting tools N. Z. Yussefian, P. Koshy McMaster University, Canada S. Buchholz, F. Klocke RWTH Aachen University, Germany

  2. Edge preparation of cutting tools hone chamfer ~ µm • Influences chip formation • Affects surface integrity • Precludes catastrophic tool failure • Enhances tool life & coatability • Ensures consistent tool performance nose radius chip tool work edge radius measured in X-Xplane Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  3. Influence of edge radius on carbide inserts Bouzakis et al (2002) • An increase in edge radius from 8 µm to 35 µm • Delay in the onset of coating fracture • Four-fold improvement in tool life Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  4. Enhancement in high speed steel tool life Rech et al (2005) • Edge honing enhanced the life of ground tools by ~400% • Existence of an optimal cutting edge radius Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  5. Edge honing processes brush honing micro blasting www.comcoinc.com www.osborn.com • As high as ~50% variability in edge radius (Schimmel et al, 2000) • Variability between edges as well as along the same edge • Manufacturers hence generally specify edge hones in a range • Somewhat limited when processing polycrystalline diamond tools Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  6. Edge rounding in EDM tool wear in EDM rounded edges Possibility of honing cutting edges by sink EDM hone sharp honing Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  7. Electro-erosion edge honing • Honing of tools by sinking them into an appropriate counterface • The high level of precision in EDM could address the variability issue • Tools could be processed irrespective of material hardness tool counterface The volume of material removal associated with hone generation is very minimal The relatively low material removal rate of sink EDM is of little consequence Conservative EDM parameters may be employed with a view to preserving the integrity of the surface Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  8. Kinematic configurations feed Y tool symmetric hone X Z counterface rotation of tool aboutZaxis rotation aboutXaxis asymmetric hone increasing radius along the edge Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  9. Experimental • Proof of concept & shape evolution • Assessment of tool performance & edge geometry Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  10. Measurement of edge radius NURBS model point cloud data circular regression on profile data confocal microscope Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  11. Effect of counterface material on edge geometry cutting edge • Aluminum counterface • Honed edge • Wear ratio = 0.5 counterface • Copper counterface • Chamfered edge • Wear ratio = 7.5 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  12. Geometric simulation of electro-erosion honing sparking across closest gap material removal from electrodes as per wear ratio electrode feed to restore gap width Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  13. Comparison of simulation with experiment wear ratio = 0.5 wear ratio = 7.5 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  14. Mechanism of edge generation chamfer “high” wear ratio tool counterface hone “low” wear ratio Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  15. Concept of a threshold wear ratio • A wear ratio much higher than the threshold results in the generation of a chamfer • A wear ratio much lower than the threshold results in extensive in-feed of the tool into the counterface wear ratio = 7.5 feed tool rβ For β = 90°, rβ = 40 µm & s = 15 µm, threshold wear ratio = 0.4 s β wear ratio = (Vt /Vc) counterface Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  16. Electro-erosion honed surfaces ground EE-honed high speed steel cemented carbide 200 µm extensive in-feed of cutting edge into counterface (wear ratio ~ 0.01) Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  17. Time evolution of edge geometry • Absolute radial deviation from fit circle is ~5% of edge radius fit circle a tool a work 120 s (rβ= 40 µm) b b ground edge 30 s (rβ= 22 µm) 60 s (rβ= 33 µm) • Concept of relative duty (Crookall & Fereday, 1973) Greater rate of recession on b-b compared to a-a Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  18. 100 10 1 20 25 30 35 40 45 50 • Comparison of tool life • Variable speed tool life test (Armarego & Brown, 1969) Annealed AISI 1045; dry cutting 0.15 mm feed; 0.5 mm depth of cut 300 µm max. flank wear tool life criterion EE-honed edge Tool life (min) ground edge Cutting speed (m/min) • Significant increase in tool life due to: • Electro-erosion edge honing offsetting the negative influence of grinding-induced micro-chipping • Reduction in the maximum tool temperature on account of enhanced heat transfer associated with larger contact area Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  19. Variability in edge geometry Boxes and whiskers refer to 25/75 and 1/99 percentiles, respectively 45 40 Edge radius (µm) 35 30 25 1 2 3 4 5 6 Edge number • 140 measurements over an edge length of 10 mm (edge 1 above) indicated a mean of 32.1 µm and standard deviation of 1.6 µm, which refers to a variability of ~15% • This is a significant improvement over conventional processes wherein the corresponding variability could be on the order of 50% about the mean radius Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60thCIRP General Assembly Pisa, August 25, 2010

  20. Conclusions • The application of electrical spark discharges for edge honing has been demonstrated • The counterface material plays a critical role in the geometry of the generated edge • Edge hones generated by electro-erosion honing significantly improved the life of ground tools • Electro-erosion honing corresponds to robust edge geometry generation as compared to conventional processes Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60th CIRP General Assembly Pisa, August 25, 2010

  21. Thank you for your kind attention! C4 Consortium of Ontario Canadian Network of Centers of Excellence Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60th CIRP General Assembly Pisa, August 25, 2010

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