How does precision machining of plastic mold parts achieve its legendary status through the combined use of wire EDM and mirror EDM?
Publish Time: 2026-02-20
Behind the mass production of plastic products, mold precision directly determines product quality and production efficiency. The dimensional tolerances, surface finish, and wear resistance of precision machining of plastic mold parts directly affect injection molding results and mold lifespan. Traditional machining methods struggle to meet micron-level precision requirements, while the synergistic application of wire EDM and mirror EDM is becoming the golden combination for precision manufacturing of plastic molds.1. Process Positioning: Division of Labor and Collaboration between Wire EDM and EDMWire EDM and mirror EDM each have their strengths in mold manufacturing. Wire EDM is mainly used to process the contours, holes, and complex curves of mold inserts. Utilizing a continuously moving fine metal wire as an electrode, it removes material through pulsed discharge, achieving a dimensional accuracy of ±0.002mm. Mirror EDM focuses on the finishing of the core surface, using copper or graphite electrodes to perform contour discharge on the workpiece surface, achieving a mirror effect with a Ra of less than 0.1μm. The two processes have a clear division of labor and complementary advantages: wire EDM is responsible for the "shape," while EDM is responsible for the "surface," together constructing a complete precision system for mold parts.2. Advantages of Wire EDM: Precise Shaping of Micron-Level ContoursWire EDM has unique advantages in the manufacturing of mold inserts. The filament diameter can reach 0.03 to 0.3 mm, enabling the machining of extremely small rounded corners and narrow gaps, suitable for the complex contours of precision inserts. Slow wire EDM employs a multi-cutting process, with an initial rough cut leaving a margin, followed by 2 to 3 finishing cuts to gradually improve precision, ultimately controlling the dimensional tolerance within 0.005 mm. During machining, the workpiece and electrode wire do not directly contact each other, eliminating cutting force and preventing deformation of thin-walled parts. Simultaneously, wire EDM can machine quenched materials with a hardness of HRC60 or higher, eliminating the need for pre-machining followed by heat treatment of inserts, reducing the risk of heat treatment deformation, and ensuring stable and reliable final precision.3. Mirror-Finish EDM: The Ultimate Pursuit of Surface QualityMirror-finish EDM is a key guarantee for the surface quality of mold cores. Traditional electrical discharge machining (EDM) leaves noticeable discharge marks on the surface, requiring subsequent polishing. Mirror EDM, however, optimizes pulse parameters, using extremely short pulse widths and high-frequency discharge to reduce the discharge pit diameter to the micrometer level, directly achieving a mirror finish. The surface Ra value can reach 0.05 to 0.2 μm, meeting high-gloss injection molding requirements without polishing. This is particularly important for transparent and exterior molds, avoiding dimensional changes and rounded edges caused by polishing. Mirror finishing also creates a uniform micro-dimpled structure on the surface, facilitating demolding, reducing wear, and significantly extending mold life.4. Material Compatibility: Perfect Match Between Carbide and Tool SteelPrecision machining of plastic mold parts commonly uses materials including carbide, SKD61 tool steel, and S136 stainless steel, which are high in hardness and difficult to machine. Both wire cutting and mirror EDM are non-contact thermal processing methods, not limited by material hardness, and can easily machine carbide inserts with a hardness of HRC65 or higher. Wire EDM uses deionized water as the working fluid, providing excellent cooling and suitable for cutting high-hardness materials. Mirror EDM uses a specialized oil-based working fluid, ensuring stable discharge and superior surface quality. The combination of these two processes allows mold parts to be precision-machined after heat treatment, eliminating the effects of heat treatment deformation and ensuring that the final dimensional accuracy and surface quality meet design requirements.5. Precision Control: Comprehensive Guarantee from Programming to InspectionPrecision machining of plastic mold parts relies on comprehensive precision control throughout the entire process. Before machining, a coordinate measuring machine (CMM) is used to inspect the blank and establish a precise machining datum. During the programming stage, CAD/CAM software is used for path optimization to avoid overcutting or undercutting. During machining, discharge parameters are monitored in real time, automatically compensating for electrode wear and wire diameter changes. Wire EDM employs a tension control system to maintain stable electrode wire operation; mirror EDM is equipped with an adaptive control module that dynamically adjusts pulse energy according to the machining status. After machining, a CMM is used again for inspection; key dimensional tolerances must reach IT5 level, and surface roughness is measured using a profilometer to ensure that every indicator meets the drawing requirements.6. Extended Lifespan: Dual Benefits of Low Wear and High StabilityThe synergistic application of wire EDM and mirror EDM ultimately results in a significant extension of mold lifespan. High-precision inserts and cores have uniform clearance, resulting in a more rational stress distribution during injection molding and reducing localized wear. The mirror surface reduces flow resistance of the plastic melt, lowering demolding force and preventing tearing or sticking. The machined surface is free of micro-cracks and residual stress, improving fatigue resistance and allowing the mold to withstand more injection cycles. Actual statistics show that mold parts manufactured using these two processes can have a 30% to 50% longer service life than those manufactured using traditional methods, reducing maintenance frequency and significantly lowering overall production costs.Wire EDM and mirror EDM perfectly complement each other in the precision machining of plastic mold parts. From contour accuracy to surface quality, from material compatibility to lifespan extension, they jointly construct a high-precision technological barrier. They are not merely choices of processing techniques, but core guarantees of mold quality and competitiveness, providing solid support for the high-quality production of plastic products and continuing the high-precision legend in the field of precision manufacturing.
