5 Levels Of Plastic Mold Maintenance-5.Major Maintenance

- Sep 19, 2018-

This maintenance should be performed by skilled tool and die personnel. It should be done when triggered either by the mold fulfilling  required number of cycles for maintenance, excessive wear or damage to the tool. Record keeping here is quite important. Before maintenance begins, there should be four complete shots (Parts,sprues and runners) delivered with the tooling for study. Two shots should be from the initial mold qualification. This gives a visual record of what was acceptable when the mold was new and fully functioning. The second two shots should be the most recent parts produced before the tool was pulled for maintenance. Comparison of the before and after shots will give an excellent indication of wear and abuse the tool has suffered.All components determined and authorized to be replaced should be removed and new components constructed and installed in accordance to the original designs if previously certified spare components are not available.Worn leader pins, bushings and all bearing moving surfaces should be checked for wear and replaced/repaired as required.Plates and mold cavity surfaces should be checked for parallelness and ground flat if required.Mold cavity surface should be cleaned and polished as required to the original surface requirements. Galling, dings and dents should be worked out until the surfaceis fully in compliance to the original print specifications.All components not meeting the part print’s original specifications should be repaired, replaced and requalified as required.All components that have been plated should be stripped and replated where quired. All components that have had special surface treatments for corrosion resistance, lubricity, hardness and the like should be retreated to insure the original intent of the tool.All moving components should be checked for ease of movement. Adjustments should be made as required. All return springs in the ejector plate should be replaced with new springs to avoid fatigue.All water lines should be flushed with descaling agent to remove scale build up. All”O” rings, internal plugs, seals and gaskets should be replaced.For tools requiring high production, the cavities should be removed and stress relieved to remove work hardening and material embrittlement. The entire mold/cavity set must be reinspected and requalified as though it was a new cavity.The mold base is to be inspected for cracks, work hardening, corrosion, etc. If the mold base was plated or painted for corrosion resistance, the coating is to be stripped, the base cleaned and the coating reapplied. The mold’s ID is to be redone indicating the tool was rebuilt.
The cavity surface is to be inspected for wear or erosion of plating or texturing. When determined necessary, the cavity surfaces are to be stripped and replated, or the texture is to be polished off and then new texture applied 250,000 cycles or half the anticipated life time volume