22 years of industry experience in mechanical parts manufacturing


Precision machining - - Introduction to spark machine processing principle

by:HENRY PARTS     2021-04-12
More for electrical discharge machining, the tool electrode and workpiece, respectively, after pulse power poles, and into working liquid, or the working fluid filling the discharge gap. Through clearance control tool electrode to the workpiece feeding automatic control system, when the gap reached a certain distance between the two electrodes, a pulse voltage applied on two electrodes will be working liquid breakdown, produce the spark discharge. Instantaneous concentration in the micro channel discharge a large amount of heat, the temperature can be as high as 10000 ℃ above, the pressure also has changed dramatically, which makes this work surface local trace metal material melt immediately, gasification, and explosive spatter to the working liquid, rapid condensation, form a solid metal particles, was taken away by working liquid. At this time in workpiece surface traces of a tiny pits, discharge brief pause, restoration of working liquid insulation state between the two electrodes. Then, the next pulse voltage and breakdown at these two electrodes are relatively close to another point, spark discharge, repeat the above process. So, while each pulse discharge removal in a little amount of metal, but because there are thousands of times per second pulse discharge effect, the more metal, can be certain productivity. In keeping the tool electrode and workpiece under the condition of constant discharge gap between the workpiece side be metal, while the tool electrode to the workpiece feeding, finally and work out corresponding to the shape of the tool electrode shape. Therefore, as long as change the shape of the tool electrode and the relative motion between the tool electrode and workpiece, it can work out all kinds of complex profile. Tool electrode used good electrical conductivity, high melting point, easy processing electrical erosion resistance of materials, such as copper, graphite, copper tungsten and molybdenum alloy, etc. In the process of machining, the tool electrode also has the loss, but less than the quantity of metal workpiece removal in, or even close to the lossless. Working liquid medium as a discharge, also in the process of machining plays a cooling and chip removal, and so on. Common working liquid is low viscosity, high flash point, stable performance of medium, such as kerosene, deionized water, emulsion and so on. Edm machine is a kind of self-excitation discharge, its characteristic is as follows: the spark discharge between two electrodes with high voltage before discharge, when the two electrodes is close to in medium is breakdown, the ensuing spark discharge. Along with the breakdown process, the resistance between the two electrodes decreases sharply, the voltage between two poles also sharply lower. Spark channels must remain in short time ( Usually 10 - 7 - 10 - 3s) In a timely manner after go out, only can keep the spark discharge characteristics of 'cold' ( The channel energy conversion of thermal energy too late to electrode depth) To channel energy in minimum range. Channel energy, can make the electrode local corrosion. Using the spark discharge when the size of materials processing, the method of corrosion phenomenon called edm. Edm is within the scope of the low voltage, spark discharge in liquid medium. Electric spark machining according to relative motion between tool electrode and the workpiece in the form of the characteristics of edm method can be divided into five categories: use of molding tool electrode, relative to the workpiece as simple feed movement of the electric spark forming processing; Axial moving of wire is used as the tool electrode and workpiece according to the required shape and size as trajectory, to cut conductive material in wedm processing; Metal wire or forming conductive wheel is used as the tool electrode, the small hole grinding or form grinding edm grinding; Used for processing thread ring gauge, thread plug gauge, gear and other conjugate rotary edm processing; Hole processing, carving the surface alloying and surface strengthening, and other types of processing. Electro discharge machining can normal machining method of cutting material and complex shape workpiece; When processing without cutting force; Don't produce the defect such as burr and daogen grooves; Tool electrode materials without hard than the workpiece material; Direct use of electricity processing, easy to realize automation; After processing surface metamorphic layer, in some applications to further remove; The working liquid purification and processing of smoke pollution more troublesome.
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