Comparative experimental study of machining characteristics of air-mixed EDM and conventional EDM

A new method of electrical discharge machining （EDM） in air-mixed medium--air-mixed EDM was presented, and comparative experiments were carried out to compare the machining characteristics of air-mixed EDM with conventional EDM. The experimental results showed that better machining performances were obtained with tool electrode as the cathode and workpieee as the anode. It was found that the material removal rate （MRR） was higher, the tool electrode relative wear ratio （TWR） was lower and the surface roughness （SR） quality was better in the case of air-mixed EDM than that of conventional EDM, and the reasons bringing out the results were analyzed.

Effect of Free-cutting Additives on Machining Characteristics of Austenitic Stainless Steels

The machinability tests were conducted by using a YD-21 dynamometer on a CA6161A lathe.The experiments were conducted to determine the effect of free-cutting additives on machining characteristics of austenitic stainless steels.The conventional austenitic stainless steel 1Cr18Ni9Ti（steel A） and the free cutting austenitic stainless steel（steel B） were prepared.The results have shown that machinable inclusions were composed of MnS and CuO,and they might be also Ti4C2S2.The presence of Bi in the inclusion was detected by the atom map and electro-probe microanalysis（EPMA）,which might be one of the most important factors to improve the machinability of austenitic stainless steels.The cutting forces for steel B were lower than those of steel A at various cutting speeds;the abrasion depth of the flank of the tool for steel B was less than that of the steel A under the same cutting conditions.The machinability of austenitic stainless steel was visibly improved by adding free-cutting additives,such as S,Cu and Bi.Ultimate tensile,yield strength,and total elongation values of the free cutting austenitic stainless steel were improved due to the addition of these free-cutting additives.

CUTTING REGULARITY AND DISCHARGE CHARACTERISTICS BY USING COMPOSITE COOLING LIQUID IN WIRE CUT ELECTRICAL DISCHARGE MACHINE WITH HIGH WIRE TRAVELING SPEED

The analysis of cutting regularity is provided through using and comparing two typical cooling liquids. It is proved that cutting regularity is greatly affected by cooling liquid＇s washing ability. Discharge characteristics and theoretic analysis between two electrodes are also discussed based on discharge waveform. By using composite cooling liquid which has strong washing ability, the efficiency in the first stable cutting phase has reached more than 200 mm^2/min, and the roughness of the surface has reached Ra〈0.8 μm after the fourth cutting with more than 50 mm^2/min average cutting efficiency. It is pointed out that cutting situation of the wire cut electrical discharge machine with high wire traveling speed （HSWEDM） is better than the wire cut electrical discharge machine with low wire traveling speed （LSWEDM） in the condition of improving the cooling liquid washing ability. The machining indices of HSWEDM will be increased remarkably by using the composite cooling liquid.

从第七届中国国际机床展览会谈我国机床工业的挑战与对策

The seventh Chinese international machine tool exhibition is hold in Peking. This exhibition has such characteristic that the machine tools are mainly numerical controlled ones, and that it is the general trend, that the machine tools have some functions of the personal computers, and that the exhibition of the five axle joint movement machine tools show that we have made a great break-through on the field, and that the nanometer machine tools draw so much attention on it and that the cutting speed are becoming higher and higher. The developing direction of our machine tool industry depends on strengthening to adjust the calling and that the enterprise must complete the reformation to itself and carrying forward enterprise informationizing and strenthening scientific research.