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.
Mold Parting Line Re-Spotting
Meaning
Tool maintenance is necessary when the mating surfaces of the cavity and core plates develop wear or minor deformities that allow polymer flash to escape. Through mold parting line re-spotting, toolmakers apply a thin layer of transfer pigment to one half of the tool, close the press under clamp pressure, and manually grind down high spots revealed by the transfer pattern. This iterative process restores the perfect seal along the parting line to prevent flashing during high-pressure injection.
Process Execution
Manual benching is a highly skilled craft that ensures the tool plates seal tightly along complex three-dimensional contours. During mold parting line re-spotting, the transfer dye indicates exactly where the metal-to-metal contact is too heavy, which would prevent other areas of the parting line from sealing. By carefully scraping or polishing these areas, the toolmaker achieves a uniform seal across the entire surface.
Flash Prevention
Flashing is a common defect that occurs when the pressure of the polymer melt forces the mold plates apart at the parting line. Applying mold parting line re-spotting cures this defect by ensuring that the clamp force is distributed evenly across the sealing surfaces of the tool. This repair is particularly important when running low-viscosity resins like nylon, which can flash through gaps as small as a few microns.
Production Downtime
Scheduled tool maintenance must balance the cost of press downtime against the risk of producing defective parts. While mold parting line re-spotting requires the tool to be removed from the press, it extends the overall life of the mold.