There are many ways and methods to improve the machining accuracy of electrical discharge machining (EDM) machines. Here are a few of the more influential ones.

Reduce the vibration of molybdenum wire

The vibration sources of molybdenum wire include commutation vibration of the wire storage drum, vibration of the guide wheel (including radial runout and yaw, etc.), and electric spark discharge force. The vibration of the wire frame caused by the reversing of the wire storage drum also affects the dynamic stability of the molybdenum wire. The following analysis is carried out from the aspects of guide wheel, wire frame, wire speed, tension and wire retaining mechanism.

Guide wheel

The vibration of the guide wheel has a direct and serious effect on the vibration of the molybdenum wire. The radial runout and swing of the guide wheel should be strictly controlled, especially the radial runout and yaw after the guide wheel and the guide wheel seat are assembled on the upper and lower line arms, which are often quite different from the original accuracy of the guide wheel. The middle plane of the V-groove of all guide wheels in the wire feeding system should be strictly in the same plane. The middle plane of the V-groove of any guide wheel deviates from this plane, or the axis of the guide wheel is not perpendicular to the plane, which will be aggravated Vibration of molybdenum wire. Therefore, it is better to have fewer guide wheels. The working environment of the guide wheel bearing is very poor. Good grease should be used and the bearing clearance should be eliminated as much as possible.

Molybdenum wire frame tool

Under the action of external vibration, the wire frame has bending deformation in addition to the overall swing. Properly increasing the size of the wire frame column in the X direction and the wire frame beam in the Z direction is beneficial to improving the dynamic stability of the molybdenum wire during operation. In addition, the connection stiffness between the wire frame column and the upper and small beams is also very important.

Molybdenum wire feeding and cutting speed

If the molybdenum wire speed is too high, the frequency of the radial circle jump of the guide wheel is also high, and the vibration amplitude of the molybdenum wire increases in a certain proportion with the frequency of the radial circle jump of the guide wheel. It can be seen that appropriately reducing the wire speed under possible conditions will help improve the accuracy of wire cutting.

The tension of molybdenum wire

If the tension is too small, it will cause frequent short circuits; it will cause unstable processing, reduce the cutting efficiency, and seriously affect the processing accuracy. If higher processing accuracy is required, the magnitude and stability of the tension must be considered. The amount of tension will cause changes in the position of the fulcrum of the molybdenum wire on the guide wheel. When the tension is too high, the fulcrum will be near the horizontal bus bar of the guide wheel. The position drifts by ΔX, and the experiment proves that when the tension is 9.8N, ΔX≈8~10 microns, when the tension increases, ΔX decreases, and when the tension decreases, ΔX increases rapidly. In addition, the difference between the molybdenum wire on the winding side and the unwinding side of the wire storage drum is different, and there is a difference between the tightening side and the loosening side of the winding side. When running forward and backward, the tension of the molybdenum wire on the upper and lower guide wheels The state is different, which forms a periodic change of ΔX, which affects the position of the molybdenum wire in space, so too little tension is not acceptable. Some manufacturers have added a constant tension mechanism to the newly produced wire-cutting machine tools, which has certain advantages in improving the slack of the molybdenum wire due to elongation, reducing the amount of molybdenum wire shaking, and making the processing stable.

The blocking mechanism of molybdenum wire

The wire blocking mechanism can indeed effectively block the vibration transmitted to the processing area. The wire blocking mechanism is very important for the WEDM machine to improve the cutting accuracy.

Reduce the thermal distortion

Heat sources such as pulse power supply, machine tool electrical appliances and working fluid tank should not be installed in the bed. If necessary, good ventilation and cooling measures should be taken.

The notes during processing of wire cut machines

In order to obtain good accuracy and roughness, all parts of the machine tool (including the wire mechanism, each guide wheel, the wire barrel, discharge parameters, working fluid, etc.) must be adjusted to a good working condition. Therefore, it is necessary to frequently maintain and adjust the machine tool to produce products with good precision and roughness.

For parts of different materials, the cutting effect is very different. When cutting general parts, the cutting effect is better; when cutting parts of some special materials (such as cemented carbide, aluminum and copper and other materials), the cutting effect is very poor, mainly as follows: the cutting efficiency is significantly reduced; Cutting dimensional accuracy and roughness become worse; the molybdenum wire, guide wheel and conductive block wear significantly faster; when cutting hard alloy, the upper and lower gem main wheels are not suitable (outer edge damage) must use ceramic guide wheels or steel main wheels ( The steel capstan must be equipped with an insulating sleeve). When cutting small arcs, special attention should be paid to the fact that the accuracy of the cutting arc will deteriorate due to the influence of materials and discharge parameters. When cutting special materials (copper, aluminum, etc.), its effect is more obvious. According to the experiment, when cutting small arcs, choosing smaller discharge parameters can better meet the machining accuracy requirements.

After 12 hours of processing, move the left and right travel switches of the wire barrel to the center by 3~5mm respectively to shorten the running stroke of the wire barrel and prevent possible wire clamping in the cutting gap.