Micro EDM is an important micro manufacturing process because it is unconstrained by the hardness or material strength of the material being machined.
Micro Electrical Discharge Technologies
Micro EDM is an important micro manufacturing process because it is unconstrained by the hardness or material strength of the material being machined. Article by Sodick.
Micro electrical discharge machining is similar with the principals of electrical discharge machining (EDM), a thermal process that uses electrical discharges to erode electrically conductive materials. EDM has a high capability of machining the accurate cavities of dies and mould. It is an effective technique in the production of micro components that are smaller than 100µm.
The main differences between micro EDM and conventional EDM are the size of the electrode used, the power supply (current and voltage), and the resolution of the X-, Y- and Z- axes movement. Micro EDM is a process based on thermoelectric energy between workpiece and electrode. In micro EDM, the pulse generator produces very small pulses within a pulse duration of a few microseconds or nanoseconds. Therefore, micro EDM utilizes low discharge energies to remove small volumes of material.
Micro EDM is an important micro manufacturing process because it is unconstrained by the hardness or material strength of the material being machined. It has a wide implementation because there is no direct contact between the electrode and machined component; hence, no contact forces are induced during the machining process. Which is why it is highly suitable for machining all types of conductive metals and semiconductors.
One example is Sodick’s AP30L linear motor-driven die-sinker EDM, which features ultra-precision machining and achieves high speed and quality surface finish by adopting the stable EDM system Arc-less 4. This series has been developed for the purpose of improving the machining accuracy and productivity of small and miniaturized high precision moulds, such as components for electronic equipment, automobiles, and digital consumer electronics, among others. Various advanced technologies are implemented in this machine in order to achieve ultra-high precision machining in the range of 1μm.
Temperature Control
In micro EDM, changes in temperature impact the machining of high precision parts. Sodick’s AP30L will collectively manage all the ambient temperature changes and internal heat generation through the overall temperature control. It is capable of optimum high rigidity mechanical structure by CAE analysis, and built with a fully separate heat source structure integrated with ceramic components and machining-fluid for temperature control. This is the upgraded model of the die-sinker EDM, featuring a newly designed main body, tank, electric discharge power supply and NC unit. The comprehensive temperature control minimizes the effects from the temperature change in the installation environment and the heat generated during high-speed drive, which used to be an issue in high-precision machining.
In order to maintain extremely accurate positioning of the X, Y and Z axis, the machine is installed with Sodick’s in-house developed linear motor, which features high-speed axis motion and quick response, made possible by its ball screw-less design. Conventional drive systems use ball screws to convert the rotational motion of the motor into the linear motion of the axis stroke, leading to the unavoidable deterioration of the high-speed servo motors due to back-lash and mechanical lost motion. However, linear motors directly provide motion to each axis without converting rotational movements of the motor to linear motion. To achieve maximum performance with a linear motor, the K-SMC motor controller is also developed in-house, utilizing Sodick’s control know-how. The feedback from the spark gap is directly fed to the K-SMC board, allowing for instantaneous adaptation of the sparking conditions.
The machine is equipped with a newly developed carbon fibre reinforced polymer (CFRP) compact symmetrical head to achieve low weight and high rigidity. In addition to the fully separate heat source and precise cooling mechanism, a newly developed precise thermal displacement compensation system makes it possible to perform high-precision machining. The system also incorporates artificial intelligence (AI) technologies.
The system’s LP4 power supply NC unit, developed and manufactured in-house, has new discharge circuits and control that significantly improve machining speeds for all processes, from rough machining to finishing. The new Arc-less 4 EDM system offers stable, high-precision machining for all types of materials. The discharge state can be maintained steadily; but speeding up is possible. In addition, it realizes suppression of electrode consumption, achieves a wide variety of processed surface quality ranging from satin finish to mirror finish, and improves the overall performance of electric discharge machining.
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