Process Window Compensation versus Tool Steel Alterations for Heavy Wall Sections
Altering tool steel to eliminate heavy wall sections cuts cycle time and unit cost far more reliably than forcing process windows past physical thermal limits.
Tool Steel Alterations
Meaning
Mechanical and chemical modification of mold inserts and cavities is performed to improve the wear resistance, heat transfer, or surface finish of injection molding tools. Through tool steel alterations, mold-makers apply thermal treatments, surface coatings, or select alternative metal alloys to address specific processing challenges like mold corrosion or abrasive wear. This engineering process ensures the mold can withstand the high pressures and temperatures of a long production run.
Wear Resistance
Processing glass-filled or abrasive polymers causes rapid wear on the mold cavities, which leads to dimensional drift and flashing. Implementing tool steel alterations such as nitriding or physical vapor deposition of titanium nitride protects the steel from abrasive wear. This coating extends the tool life and ensures that the mold retains its tight tolerances over millions of cycles.
Thermal Optimization
High-conductivity copper alloys are often substituted for standard tool steel in regions of the mold that suffer from poor cooling. In tool steel alterations, swapping P20 or H13 steel for beryllium-copper inserts in deep cores helps accelerate heat extraction. This material swap reduces the cooling phase of the molding cycle and lowers the cost per part.
Polishing Process
High-gloss cosmetic parts require mold surfaces to be polished to a mirror finish. Applying tool steel alterations like through-hardening allows the steel to be polished to a high finish without pitting or blemishes.