(1) To ensure the precision of manufacture and installation of the storage tube and guide wheel, to control the axial and radial runout of the storage tube and the guide pulley, to be flexible in the guide wheel rotation, to prevent the guide wheel from jumping and swinging, and to reduce the molybdenum wire Vibration, to promote the stability of the processing process.
(2) When necessary, the wire speed of the molybdenum wire can be appropriately reduced, and the mobilities of the molybdenum wire can be increased in both positive and negative directions, and the smoothness of the wire can be increased.
(3) According to the characteristics of wire cutting work, the high-speed movement of the molybdenum wire requires frequent commutation for processing. Molybdenum wire will cause its elasticity at the instant of reversing, and the tension of the molybdenum wire is not uniform, thus causing molybdenum wire vibration, directly The roughness of the machined surface is affected, so the number of commutation times of molybdenum wire movement should be minimized. Tests have proved that under the same processing conditions, increasing the effective working length of molybdenum wire can reduce the number of commutation times of molybdenum wire, reduce the jitter of molybdenum wire, promote the stability of the processing process, and improve the surface quality of machining.
(4) Wrap the molybdenum wire around the storage tube with a dedicated mechanism to ensure that the molybdenum wire is tightly and evenly arranged. As far as possible, manual winding is not used, because it is difficult to ensure that the molybdenum wire is arranged evenly and elastically on the wire storage drum. Loose tightness, the tension of the molybdenum wire is not the same, it will cause the molybdenum wire jitter in the work, thereby increasing the surface roughness.
(5) The smoothness of the movement of the X-direction and Y-direction table and the uniformity of the feed also affect the roughness of the machined surface. The method of ensuring the smooth movement of the X-direction and Y-direction worktables: first test cut, uniform frequency conversion during the molybdenum wire reversal and wire moving, and walk the X-direction and Y-direction straight line separately, the stepping motor is in the forward and reverse direction of the molybdenum wire. The number of steps taken should be approximately equal, indicating that the frequency conversion adjustment is appropriate and that the molybdenum wire is tight and uniform, which can ensure the smooth movement of the table.
(6) For machine tools with adjustable wire racks, the wire rack span should be reduced as much as possible. If the span is too large, molybdenum wire will vibrate and the span is too small, which is not conducive to the coolant entering the processing area. Such as cutting 40mm thick workpiece, wire frame span between 50 ~ 60mm, the upper and lower wire rack cooling nozzle from the workpiece surface 6 ~ 10mm, this can improve the rigidity of the molybdenum wire in the processing area, to avoid molybdenum wire vibration, conducive to processing stable.
(7) The feed rate of the workpiece should be appropriate. In the online cutting process, if the feed rate of the workpiece is too large, the corroded metal particles are not easily discharged, which may cause short-circuiting of the molybdenum wire and increase the instability of the machining process. If the workpiece feed rate is too low, the production efficiency is high. low.
(8) Pulse power is also an important factor influencing the roughness of the machined surface. The pulse power source uses a rectangular wave pulse because its pulse width and pulse interval are continuously adjustable and are not easily affected by various factors. Reducing the energy of a single pulse can improve the surface roughness. The factors affecting the energy of a single pulse include the pulse width, the number of power amplifier tubes, and the peak current of the power amplifier tube. Therefore, reducing the pulse width and reducing the peak current can improve the surface roughness. However, reducing the pulse width, the production efficiency is greatly reduced, and is not available; reducing the peak current of the power amplifier tube, the production efficiency will also be reduced, but the impact degree is smaller than the reduction of the pulse width. Therefore, the author thinks that reducing the peak current of the power amplifier tube, appropriately increasing the pulse width, and adjusting the appropriate pulse interval can not only improve the production efficiency, but also obtain a low processing surface roughness.
(9) Maintain a stable power supply voltage. Because the power supply voltage is not stable, the voltage across the molybdenum wire and the workpiece may be unstable, resulting in unstable breakdown discharge process and increased surface roughness.
(10) The wire cutting fluid must be kept clean. If the working fluid is used for a long time, the metal particles will gradually become larger, so that the nature of the working fluid will change, the working fluid will be reduced, and the cooling system will be blocked. Therefore, it is necessary to filter the working fluid for a long time. Replace working fluid. The simplest method of filtration is to place a sponge at the pumping hole of the cooling pump. The working fluid preferably wraps the molybdenum wire in a spiral form to increase the absorbing effect of the working fluid on the vibration of the molybdenum wire, reduce the vibration of the molybdenum wire, and improve the surface roughness.
In short, as long as the instability of the machining process is eliminated and the working fluid is kept clean, better surface roughness can be obtained with higher production efficiency.
Measures to Improve the Surface Roughness of Wire Cutting
The main reason for the surface roughness of wire-cut electric discharge machining is that the machining process is unstable and the working fluid is not clean. The following improvement measures are proposed.