EDM Overview – EDM – Machine Tool Industry
EDM equipment is CNC machine tools The scope of EDM in some liquid medium, the use of pulsed electric discharge on the corrosion of the conductor material to ablation of material, so that parts of the size, shape and surface quality for the intended technical requirements of a processing method. In machining, electrical discharge machining is widely used, especially in mold manufacturing, aerospace and other fields has a very important position. 1, Principles and characteristics of EDM
EDM is shown in the processing system as carried out. Process, a pulsed power pole access tool electrode, the workpiece electrode connected to another pole, poles are immersed in a liquid with a certain degree of isolation medium (used kerosene or mineral oil or deionized water). Tool electrode feed from the automatic adjustment device control to ensure that tools and workpiece in the normal working hours to maintain a small discharge gap (0.01 ~ 0.05mm). When the pulse voltage is added between the two poles, they put under extreme time between the nearest point of the liquid dielectric breakdown, the formation of plasma channel. As the channel cross-sectional area is small, the discharge time is short, resulting in a high concentration of energy (10 6 10 7 W / mm 2 ), Discharge zone, resulting in the instantaneous high temperature enough to melt even the material evaporation, resulting in a small pit. After the first pulse discharge, after a very short time interval, the second pulse it in another very recent Breakdown of discharge between. Such a high frequency, the cycle continues again and again, the tool electrode to the workpiece to keep it on the shape of the final copy in the workpiece, the formation of the required surfaces. At the same time, a small portion of total energy is also released into the tool electrode, resulting in tool wear.
EDM schematic From the above description can be seen, for EDM must have three conditions: pulse power must be used; must use automatic feed adjustment device to maintain tool electrode and workpiece electrode discharge gap between the minor; spark discharge must have certain dielectric strength (10 3 10 7 ? M) to the liquid medium. EDM has the following characteristics: can process any high-strength, high hardness, high toughness, high brittleness and high purity conductive material; processing without obvious mechanical force applied to the low stiffness of the workpiece and the micro-structure processing: pulse parameters can be based on adjustment is required, can be conducted on the same machine roughing, semi-finishing and finishing; EDM surface display after the pits, oil storage and help reduce noise; productivity than cutting; discharge some Energy consumption in the tool electrode, the electrode loss, affecting the precision forming. 2, the application of EDM EDM is mainly used for the production of type mold hole, cavity machining, mold manufacturing industry has become the leading processing methods, the mold industry to promote technological progress. EDM in 3000 the number of parts below, than die stamping parts economically more reasonable. Process by process tool and the workpiece relative motion of the characteristics and use different EDM can be divided into: EDM machining, EDM wire cutting, EDM grinding, EDM, non-metallic electric spark electrical discharge machining and surface enhancements. (1) EDM electrode that is relative to the workpiece through the tool for feed motion, the workpiece electrode shape and size reproduction of the workpiece, thereby processing the necessary parts. It includes spark perforation cavity machining and processing of two kinds. EDM cavity machining is mainly used for processing various types of hot forging dies, die casting dies, extrusion dies, plastic and bakelite membrane cavity. EDM machining is mainly used for piercing type hole (round hole, square hole, polygon hole shaped holes), curve hole (curved hole, screw hole) and small and micro processing. In recent years, in order to solve the cross-section of small hole machining electrodes, deformation, hole depth to diameter ratio, chip removal difficult issues such as perforation of the EDM machining process in the development of high-speed small hole made good social and economic benefits. (2) WEDM the method is the use of mobile tools for fine wire electrode, according to a predetermined trajectory pulse discharge cutting. By moving the speed wire electrodes were divided into low-speed High Speed Wire and Wire Cutting. China's general use of high-speed WEDM in recent years is the development of low-speed Wire Cutting, High Speed Wire, the wire electrode is 0.02 ~ 0.3mm diameter high-strength molybdenum wire, reciprocating speed of 8 ~ 10m / s . Low-speed wire walking, the more use of copper wire, wire electrode to less than 0.2m / s speed for one-way low speed. Line cutting, the electrode wire constantly moving, their loss is very small, and therefore higher precision. The average precision of up 0.0lmm, much higher than the EDM. Surface roughness R a Values up to 1.6 or less. Most CNC WEDM abroad have adopted different levels of computer CNC System Basically realized NC WEDM. WEDM is widely used in the current processing of various stamping die (punching and blanking with a), model, and various forms of complex holes, such as surface and narrow. 3, EDM trends EDM in improving the accuracy and automation, it is also the structure of miniaturization. To improve machining accuracy, similar to the Machining Center Precision multi-function micro-EDM machine by the favor, in this machine, from the production of micro electrodes to the micro-machining, the electrode in a single setup, thus reducing the number of clamping electrodes caused by error, and can be re-processed through the electrode to modify the shape of the electrode by loss, thus enhancing the machining accuracy. In this machine, it can be achieved EDM wire electrode grinding, EDM micro hole machining complex shapes and functions such as electrical discharge milling, and is expected to realize three-dimensional shape of micro-EDM machining. Current advanced multi-axis EDM CNC trend is multi-functional in one of these features include rotary indexing, automatic exchange of electrodes, automatic discharge gap compensation, current adaptive control and real-time intelligence processing Criteria selection, in order to achieve the criteria may choose from the process to automate the whole process of machining parts, Chamier company, Archie, Mitsubishi Electric Corporation, Sodick EDM famous foreign companies have mature product machine manufacturers, the domestic machine tool plant Hanchuan , Chengdu, Beijing Dimon radio companies and special equipment factory are producing such products. Small direct-drive electrode EDM system 90 before the 20th century, the appearance of a
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