Abrasion Assisted Wire EDM

I. Menzies, P. Koshy McMaster University, Canada

Assessment of Abrasion-Assisted Material Removal in Wire EDM

58th CIRP General Assembly, ManchesterAugust 25, 2008

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Assessment of abrasion-assisted material removal in wire EDMI. Menzies, P. Koshy

58th CIRP General AssemblyManchester, August 25, 2008

generator technologycoated wireshigh pressure flushingadaptive control

workpiece height & taper surface finishmachining accuracy & precision

1970

Kruth et al (2004)

cutting rate3/20



Machining speed & surface integrity continue to be issues of focus in current wire EDM research

~40X

Aspinwall et al (2008)

rough

trim

surface integrity

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The issues of machining speed and surface integrity are interlinked

Aspinwall et al (2003)

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Enhancing the ejection efficiency is the key to simultaneously improving the removal rate and the surface integrity

Need for innovation

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Hybrid machining entails the integration of processes with distinct mechanisms of material removal to exploit their synergy El-Hofy (2005)

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Grinding + EDMThermal softening of workpieceIn-process dressing & declogging

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Extension of the concept to wire EDM

Different from Wire Electro Discharge Grinding

wire rod

discharge area

Masuzawa et al (1985)

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ph > gw

Material removal by melting/vaporization and two-body abrasion

wire

reference voltagedielectric strength

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Fixed abrasive diamond wire used in the electronics industryIssues with wire guide and electrical power feed

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wire failure by embrittlementexperiments using wire with no abrasives for comparison of removal rate & recast layer, and estimation of gap-width

average voltage 108 –162 Vpeak current 1.2 – 8 Aopen voltage 180 V

on time 4.9 μs

off time 100 μs

wire tension 6.8 N

wire speed 5.5 m/min

SAE 1018 steel & Nickel 600

dielectric oil; 1 bar flushing pressure

machining gap 8 – 20 µmremoval rate 0.02 – 0.10 mm2/min

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50 m

180 micron core 50 micron (nominal) diamond

Wire characterization

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Force measurement by considering force equilibrium in reference to wire bow and wire tension

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edm

Order of magnitude enhancement in the removal ratewire sawing

Steepest gradient in the increase in removal rate is in line with the maximum force gradient

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Increase in the removal rate is due to abrasion

20 m

162 V, 8 A

108 V, 8 A

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abrasion-assisted

Wire performance degrades rapidly

with repeated use

wire-EDM

108 V, 8 A

Machined surface

used wire

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Comparison of recast material

nickel steel

wire-EDM

abrasion-assisted

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Wire feed strategies

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Conclusions & OutlookProof-of-concept of an innovative abrasion-assisted wire EDM process has been presentedThe process has the potential to significantly enhance the removal rate and the quality of the machined surface, particularly for metal matrix composites that are difficult to wire EDMThe process is perhaps best implemented on a twin-wire machine toolResearch effort is required to formulate wires with aluminum oxide abrasives, with a core that has good sparking and grain retention characteristicsElectrical discharges could possibly enhance wire sawing of brittle materials through controlled thermal shock-induced fracture

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Thank you for

your attention! Natural Sciences & EngineeringResearch Council of Canada

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Abrasion Assisted Wire EDM

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