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

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Presentation on theme: "N. Z. Yussefian, P. Koshy McMaster University, Canada S. Buchholz, F. Klocke RWTH Aachen University, Germany Electro-erosion edge honing of cutting tools."— Presentation transcript:

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

2 2/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Edge preparation of cutting tools tool chip work Influences chip formation Affects surface integrity Precludes catastrophic tool failure Enhances tool life & coatability Ensures consistent tool performance ~ µm chamfer hone nose radius edge radius measured in X-X plane

3 3/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 An increase in edge radius from 8 µm to 35 µm Delay in the onset of coating fracture Four-fold improvement in tool life Bouzakis et al (2002) Influence of edge radius on carbide inserts

4 4/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Edge honing enhanced the life of ground tools by ~400% Existence of an optimal cutting edge radius Enhancement in high speed steel tool life Rech et al (2005)

5 5/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 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 Edge honing processes micro blasting brush honing

6 6/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Possibility of honing cutting edges by sink EDM tool wear in EDM rounded edges Edge rounding in EDM hone sharp honing

7 7/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 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 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 counterface tool Electro-erosion edge honing The volume of material removal associated with hone generation is very minimal

8 8/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Kinematic configurations symmetric hone tool counterface feed increasing radius along the edge rotation about X axis X Y Z asymmetric hone rotation of tool about Z axis

9 9/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Experimental average voltage80 V peak current1.8 A polaritytool (−) pulse on-time0.6 µs duty factor 50% machining time80 s AISI T-15 High Speed Steel Aluminum counterface Finish ground SNEA 320 inserts 10 mm edge length; 90° wedge angle Dielectric oil; no external flushing Proof of concept & shape evolution Assessment of tool performance & edge geometry

10 10/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Measurement of edge radius confocal microscope NURBS model circular regression on profile data point cloud data

11 11/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Effect of counterface material on edge geometry Aluminum counterface Honed edge Wear ratio = 0.5 Copper counterface Chamfered edge Wear ratio = 7.5 cutting edge counterface

12 12/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Geometric simulation of electro-erosion honing sparking across closest gap material removal from electrodes as per wear ratio electrode feed to restore gap width

13 13/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Comparison of simulation with experiment wear ratio = 0.5wear ratio = 7.5

14 14/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 tool counterface Mechanism of edge generation “high” wear ratio “low” wear ratio chamfer hone

15 15/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Concept of a threshold wear ratio tool counterface s rβrβ feed β For β = 90°, r β = 40 µm & s = 15 µm, threshold wear ratio = 0.4 wear ratio = 7.5 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 = (V t /V c )

16 16/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 cemented carbide 200 µm high speed steel ground EE-honed Electro-erosion honed surfaces extensive in-feed of cutting edge into counterface (wear ratio ~ 0.01)

17 17/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Time evolution of edge geometry 30 s (r β = 22 µm) 60 s (r β = 33 µm) 120 s (r β = 40 µm) ground edge Greater rate of recession on b-b compared to a-a tool work b b a a Concept of relative duty (Crookall & Fereday, 1973) fit circle Absolute radial deviation from fit circle is ~5% of edge radius

18 18/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Variable speed tool life test (Armarego & Brown, 1969) Comparison of tool life 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 Tool life (min) Cutting speed (m/min) EE-honed edge ground edge Annealed AISI 1045; dry cutting 0.15 mm feed; 0.5 mm depth of cut 300 µm max. flank wear tool life criterion

19 19/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 Variability in edge geometry 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 Edge radius (µm) Edge number Boxes and whiskers refer to 25/75 and 1/99 percentiles, respectively

20 20/20 Electro-erosion edge honing of cutting tools N.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke 60 th CIRP General Assembly Pisa, August 25, 2010 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 Conclusions

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


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