Len Graham Consulting

The success of any replacement/duplicate moldbuilding program is determined at the mold design stages. There is no better baseline to be able to make incremental performance improvements than an existing mold

Many mold issues can be addressed in a mold design for a replacement/duplicate mold. For molds with issues, one or more of the following examples perhaps were not appropriately applied or were not applied at all (certainly not all can be listed here, and each mold program is unique unto itself, but these are good examples of what years of practical molding production experience has told us to look for).

Wear/maintenance issues or mold foundation is not built to perform for the cycles prescribed in its SPI mold classification:

  • Improper allowance in mold components for heat expansion (primarily hot manifold applications)
  • Individual cavity alignment not used or improperly applied - plastic part P/L (parting line) has flash issues resulting from one-sided shut-off wear in alignment features
  • Steel (material) selection incompatible for high wear situations
  • Tapered shut-offs not applied where needed
  • Improper running clearances/surface finishes applied in wear areas
  • Venting location/application choice causes undue wear on other inserts or flashing
  • Improper use of platings plating is chipping
  • Latch mechanism choice too weak-unduly stressing plates and mold components
  • Shut-off areas not appropriately protected through piloting - not incorporating primary/secondary alignment
  • Slides and/or lifters are of straight and/or non-guided design and wearing prematurely
  • Unscrewing mechanism is not a good design and components are wearing prematurely
  • Not enough steel outside cavity areas for core/cavity support
  • Mold plates not appropriate thickness P/L flash mold component fracturing issues
  • Improper pre-load on inserts

Part quality issues and/or cycle is affected:

  • Previous mold steel dimensions can be changed in new mold design to bring critical part dimensions closer to center of tolerance window
  • Cavity/core cooling can be improved better part quality faster cycles
  • Plate cooling can be added
  • Features can be incorporated in design to assure part will positively stay on desired half of mold upon mold open improve cycle/part quality
  • More venting in all necessary areas secondary vents added - escaping to atmosphere
  • Inserting can be applied and secondary venting verified to allow for atmospheric bleeding of gas/air in cavity
  • Self-cleaning venting principles utilized, especially in moving situations
  • Hot manifold choice examined to assure most appropriate for plastic/part requirements
  • Part cooling issues (hot manifolds)
    • Add W/C (water-cooled) gate inserts
    • Add W/C plate cooling
    • Establish proper air insulation distance
    • Decrease manifold/drop contact area
    • Add insulator plates

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