I. Menzies, P. Koshy McMaster University, Canada

I. Menzies, P. Koshy McMaster University, Canada

Assessment of Abrasion-Assisted Material Removal in Wire EDM

58th CIRP General Assembly, ManchesterAugust 25, 2008

2/20

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

58th CIRP General AssemblyManchester, August 25, 2008

generator technology

coated wires

high pressure flushing

adaptive control

workpiece height & taper

surface finish

machining accuracy & precision

1970

Kruth et al (2004)

cutting rate

3/20



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

~40X

Aspinwall et al (2008)

rough

trim

surface integrity

4/20



The issues of machining speed and surface integrity are interlinked

Aspinwall et al (2003)

5/20



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

Need for innovation

6/20



Hybrid machining entails the integration of processes with distinct mechanisms of material removal to exploit their synergy

El-Hofy (2005)

7/20



Grinding + EDMThermal softening of workpiece

In-process dressing & declogging

8/20



Extension of the concept to wire EDM

Different from Wire Electro Discharge Grinding

wire rod

discharge area

Masuzawa et al (1985)

9/20



ph > gw

Material removal by melting/vaporization and two-body abrasion

wire

reference voltagedielectric strength

10/20



Fixed abrasive diamond wire used in the electronics industry

Issues with wire guide and electrical power feed

11/20



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 V

peak current 1.2 – 8 A

open 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 µm

removal rate 0.02 – 0.10 mm2/min

12/20



50 m

180 micron core 50 micron (nominal) diamond

Wire characterization

13/20



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

14/20



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

15/20



Increase in the removal rate is due to abrasion

20 m

162 V, 8 A

108 V, 8 A

16/20



abrasion-assisted

Wire performance degrades rapidly

with repeated use

wire-EDM

108 V, 8 A

Machined surface

used wire

17/20



Comparison of recast material

nickel steel

wire-EDM

abrasion-assisted

18/20



Wire feed strategies

19/20



Conclusions & OutlookProof-of-concept of an innovative abrasion-assisted wire EDM process has been presented

The 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 EDM

The process is perhaps best implemented on a twin-wire machine tool

Research effort is required to formulate wires with aluminum oxide abrasives, with a core that has good sparking and grain retention characteristics

Electrical discharges could possibly enhance wire sawing of brittle materials through controlled thermal shock-induced fracture

20/20



Thank you for

your attention! Natural Sciences & EngineeringResearch Council of Canada

Documents

I. Menzies, P. Koshy McMaster University, Canada