Influence of dielectric conductivity on corner error in wire electrical discharge machining of Al 7075 alloy

Comprehensive research has been carried out to investigate the effect of electrical conductivity (ĸ) of dielectric along with other process parameters in wire electrical discharge machining (WEDM) of Al 7075 alloy. Taguchi based design using L9 orthogonal array has been used to analyse the effect of open circuit voltage (VOC), pulse on time (TON), pulse frequency (fP) and servo sensitivity (SC) on corner accuracy including different other response criteria. The experimental result shows that dielectric conductivity plays a significant role in respect to corner error and surface finish in a single pass cutting operation. Surface topography and elemental analysis of the machined surface has been carried out for depth understanding of the influence of dielectric conductivity in WEDM. Experimental investigation and subsequent analysis of results showed that for a broad range of response variables (e.g. corner accuracy and surface finish) 12 mho conductivity setting gives the optimum result. However, to attain corner error (CE) and surface roughness (Ra) below a certain critical limit (i.e. CE = 0.101 mm & Ra = 2.671 µm), 4 mho conductivity setting is found to be the best setting for this alloy.

Research on Corner Control Strategy of the WEDM

Corner machining accuracy has always been one of the important properties of WEDM. In this paper, the reasons for the corner error of the WEDM were discussed. Then the mathematical deflection model of the electrode wire was established. By experimental measurements, the kerf width and the deflection of the electrode wire were obtained. Then the corner control strategy of the WEDM was proposed. Through experiment of the Comparison of corner error between control strategy with corner control and the one without corner control, it shows that the processing accuracy was improved effectively.

Analysis and Design of Wire Transport System in Microwire-Electronic Discharge Machining

A dynamic model for analyzing the wire transport system of micro w-EDM (wire electronic discharge machining) is proposed. Based on the model, two mechanisms are proposed to stabilize the wire tension. The first mechanism is the active wire feed apparatus where the wire spool is fed by a motor actively, instead of passively pulled by the windup motor. Hence, the inertia loading of the wire spool can be isolated from the system. The second mechanism is mounting a multilayer damped vibration absorber (MDVA) on the system. As the wire tension variation occurs, the MDVA oscillates to attenuate the wire tension variation. The performances of both mechanisms on the wire tension variation are theoretically investigated and experimentally validated through corner cutting on the 1.0 mm thickness tungsten carbide. Results show that the wire tension variation can be reduced from 10.3 gf to 3.3 gf after mounting the active wire feed apparatus and the oscillation frequency is increased from 13 Hz to 21 Hz. The wire tension variation can be further reduced to 1.9 gf after mounting the MDVA on the system and the high frequency perturbation is significantly attenuated. The 30-deg corner cutting shows that the corner error are significantly reduced from 26.0 μm to 12.0 μm; the standard deviation of kerf is reduced from 4.34 μm to 0.96 μm, and the surface roughness Ra is reduced from 1.15 μm to 0.63 μm after employing both developed mechanisms.

A Fast Method for Analyzing the Effect of Mask Error on Photolithography Pattern Quality

As an important factor the error of mask pattern is often ignored in the lithography simulation model. To investigate the impact of mask errors on the lithographic pattern, effects of how the wave-front on different mask pattern region affects the field points in resist is first introduced, and based on this analysis a method is proposed to quickly judge the affection of round corner error of mask pattern on the photo-resist pattern. By comparing the actual effect area and the effective wave-front area around the corner on mask pattern, the method can illustrate the quantitative relationship between variation in photo-resist pattern and the related mask error. Finally the simulation results are verified by experiments. The study results may contribute to the fast and accurate judgments of error in the lithography, and provide important theoretical basis for lithography error correction.

Analysis of the Corner Error in WEDM

This paper introduced some current researches on the corner error in WEDM and put forward the factors that have an influence on the corner error. The deflection of the wire-electrode that has been caused by discharge force, feeding directions of the wire-electrode and radial flops of the guide pulley was analyzed in detail. To minimize corner errors, the energy control strategy and the trace control strategy are presented. Especially in WEDM-HS processing, the methods improving the processing precision are given as follows: Using the over-cutting and retract program, controlling the wire-electrode tension and improving the guiding and allocation parts.