Electro Erosion Edge Honing
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Transcript of Electro Erosion Edge Honing
N. Z. Yussefian, P. KoshyMcMaster University, Canada
S. Buchholz, F. Klocke RWTH Aachen University, Germany
Electro-erosion edge honing of cutting tools
2/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Edge preparation of cutting tools
toolchip
work
Influences chip formationAffects surface integrityPrecludes catastrophic tool failureEnhances tool life & coatabilityEnsures consistent tool performance
~ µm
chamferhone
X
X
nose radius
edge radius measured in X-X plane
3/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
An increase in edge radius from 8 µm to 35 µmDelay in the onset of coating fractureFour-fold improvement in tool life
Bouzakis et al (2002)
Influence of edge radius on carbide inserts
4/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, 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)
5/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
As high as ~50% variability in edge radius (Schimmel et al, 2000)Variability between edges as well as along the same edgeManufacturers hence generally specify edge hones in a rangeSomewhat limited when processing polycrystalline diamond tools
Edge honing processes
micro blasting
ww
w.c
omco
inc.
com
brush honing
ww
w.o
sbor
n.co
m
6/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Possibility of honing cutting edges by sink EDM
tool wear in EDM
rounded edges
Edge rounding in EDM
honesharphoning
7/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Honing of tools by sinking them into an appropriate counterfaceThe high level of precision in EDM could address the variability issueTools 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
8/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Kinematic configurations
symmetric hone
tool
counterface
feed
increasing radiusalong the edge
rotation about X axis
X
Y
Z
asymmetric hone
rotation of tool about Z axis
9/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Experimental
average voltage 80 V
peak current 1.8 A
polarity tool (−)
pulse on-time 0.6 µs
duty factor 50%
machining time 80 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 evolutionAssessment of tool performance & edge geometry
10/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Measurement of edge radius
confocal microscope
NURBS model
100 150 200 250 300 350 400-50
0
50
100
150
X [m]
Y [
m]
Knot PointsEdge Cross SectionFitted Circle
circular regression on profile data
point cloud data
11/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
cutting edge
counterface
Effect of counterface material on edge geometry
Aluminum counterfaceHoned edgeWear ratio = 0.5
Copper counterfaceChamfered edgeWear ratio = 7.5
cutting edge
counterface
cutting edge
counterface
12/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, 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
wear ratio = 0.10.5
2.07.515 µm
Fig. 3. Simulated effect of wear ratio on edge geometry.
13/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Comparison of simulation with experiment
wear ratio = 0.10.5
2.07.515 µm
Fig. 3. Simulated effect of wear ratio on edge geometry.
cutting edge
counterface
wear ratio = 0.5
cutting edge
counterface
wear ratio = 7.5
14/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
tool
counterface
Mechanism of edge generation
“high” wear ratio
“low” wear ratio
chamfer
hone
15/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Concept of a threshold wear ratio
tool
counterface
s
rβfeed
β
For β = 90°, rβ = 40 µm & s = 15 µm, threshold wear ratio = 0.4
cutting edge
counterface
wear ratio = 7.5 A wear ratio much higher than the threshold results in the generation of a chamferA wear ratio much lower than the threshold results in extensive in-feed of the tool into the counterface
wear ratio = (Vt /Vc)
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Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, 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)
17/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Time evolution of edge geometry
Fig. 5. Profilometer traces of HSS edges showing their evolution.
-60 -40 -20 0 20 40 60-70
-60
-50
-40
-30 B D F H J N10 µm
-60 -40 -20 0 20 40 60-70
-60
-50
-40
-30 B D F H J N
-60 -40 -20 0 20 40 60-70
-60
-50
-40
-30 B D F H J N
unprepared edge
30 s (rβ = 22 µm)
60 s (32.6 µm)
120 s (40.3 µm)
circle fit (40.3 µm)
30 s (rβ = 22 µm) 60 s (rβ = 33 µm)
120 s (rβ = 40 µm)ground edge
a a b b
Greater rate of recessionon b-b compared to a-a
tool
workb b
aa
Concept of relative duty (Crookall & Fereday, 1973)
fit circle Absolute radial deviation from fit circle is ~5% of edge radius
18/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, 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-chippingReduction in the maximum tool temperature on account of enhanced heat transfer associated with larger contact area
20 25 30 35 40 45 501
10
100
To
ol li
fe (m
in)
Cutting speed (m/min)
EE-honed edge
ground edge
Annealed AISI 1045; dry cutting0.15 mm feed; 0.5 mm depth of cut300 µm max. flank wear tool life criterion
19/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, 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
1 2 3 4 5 625
30
35
40
45
Edg
e ra
dius
(µm
)
Edge number
Boxes and whiskers refer to 25/75 and 1/99 percentiles, respectively
20/20
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
The application of electrical spark discharges for edge honing has been demonstratedThe counterface material plays a critical role in the geometry of the generated edgeEdge hones generated by electro-erosion honing significantly improved the life of ground toolsElectro-erosion honing corresponds to robust edge geometry generation as compared to conventional processes
Conclusions
Thank you for yourkind attention!
Electro-erosion edge honing of cutting toolsN.Z. Yussefian, P. Koshy, S. Buchholz, F. Klocke
60th CIRP General AssemblyPisa, August 25, 2010
Canadian Network of Centers of Excellence
C4 Consortium of Ontario