Measures to Improve the Surface Roughness of Wire Cutting

In the context of wire-cut electric discharge machining (EDM), surface roughness is often attributed to process instability and impure working fluid. To address these issues, several improvement strategies have been proposed. Firstly, ensuring precise manufacturing and installation of the wire storage tube and guide wheel is essential. Controlling axial and radial runout, as well as maintaining smooth rotation of the guide wheel, helps prevent jumping or swaying, which in turn reduces molybdenum wire vibration and enhances machining stability. Secondly, adjusting the wire speed can be beneficial. Slowing down the molybdenum wire when necessary and increasing its mobility in both directions can improve the wire’s smoothness, leading to a more consistent cutting process. Thirdly, the frequent reversal of the high-speed molybdenum wire during cutting can cause elasticity and uneven tension, resulting in vibration. This directly affects surface finish. Minimizing the number of reversals by increasing the effective wire length has been shown to reduce jitter and improve overall surface quality. Fourthly, using a dedicated mechanism to wrap the molybdenum wire around the storage tube ensures even and tight arrangement. Manual winding should be avoided, as it may lead to uneven tension and wire movement, thus increasing surface roughness. Fifthly, the smooth movement of the X and Y-axis tables, along with uniform feed rates, plays a crucial role in surface finish. Ensuring proper frequency conversion during wire reversal and maintaining equal steps in both directions helps achieve a stable and smooth motion. Sixthly, for machines with adjustable wire racks, reducing the span between them improves rigidity and minimizes vibration. A suitable span of 50–60 mm for a 40 mm thick workpiece, with cooling nozzles positioned 6–10 mm from the workpiece surface, helps maintain stability. Seventhly, the workpiece feed rate must be balanced. Too high a feed rate can hinder chip removal, leading to short circuits, while too low a rate reduces efficiency. Eighthly, pulse power significantly impacts surface roughness. Using a rectangular wave pulse allows for better control over pulse width and interval. Reducing peak current, rather than pulse width, helps maintain production efficiency while improving surface finish. Ninthly, a stable power supply is critical. Fluctuating voltage can disrupt the breakdown process, causing unstable discharges and increased roughness. Lastly, keeping the working fluid clean is vital. Over time, metal particles can accumulate, reducing fluid effectiveness and potentially clogging the system. Filtering the fluid regularly, using simple methods like sponges at the pump inlet, and ensuring the fluid flows in a spiral around the wire can enhance its damping effect on wire vibration. In summary, by addressing process instability and maintaining clean working fluid, it is possible to achieve improved surface roughness without sacrificing production efficiency. These adjustments not only enhance the quality of the machined surface but also contribute to a more reliable and efficient machining operation.

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