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Injection mould maintenance

Posted by admin on Dec 11th, 2015

There are 5 levels of injection mould maintenance:

level 1. Routine Maintenance

Before the mold is removed from the press, it is to be heated so that all surface condensation is evaporated. With the mold still warm, internalmold surfaces should be gently cleaned with shop safety solvent to remove any residual dirt and grime, the ejector system moved fully forward, then sprayed with approved rust preventive before the ejector system is retracted and the mold closed. Lenses and highly polished surfaces should be protected following specificinstructions. All water lines should be drained and blown free of all residual water to avoid buildup of rust due to standing water. It is imperative that no water be trapped insidemold. Check and assure all bolts, plates, clamps etc. are in place and tight. Bag the last shot as an example of the typical quality of this run. Store these partswith the mold.

level 2. Simple Preventive Maintenance

Open the mold. Using properly approved safety shop solvent, remove the mold preservative with a lint free pad. It is bad practice to immediately run parts on the assumption that the first shots will scrape away the protective coating and will therefore be used to clean out the mold preservative.

level 3. Inspection Maintenance

This maintenance is performed by the lead operator or a tool maker at the end of aproduction run. Using the check list and visual inspection techniques, the mold is looked over and any minor repairs that are necessary are noted for the convenienceof the General Maintenance procedure. If not, needed repairs or future required touch up notations are kept with the mold history log for future evaluation. Any components missing or cavity blocked off should be noted and attended to. A sample from the blocked cavity should be retained for the mold maker to make repairs. The mold should be washed with safety solvent to remove the varnish and build upfrom the molding process. The vents should be checked for depth in a minimum of four clockface places aroundthe cavity face. Notations for work to be done during the General Maintenance procedure should be noted on the form for future work Bent, worn or broken ejector pins should be noted. The mold should be removed from production and the pins replaced.

Level 4. General Maintenance

Only competently trained tool room technicians should perform this maintenance. All plates are separated and their faces cleaned. Caution: Highly polished surfaces should not be cleaned with brushes or rags. Use only uncontaminated facial tissues or cotton balls. Loosen dirt by spraying cleaning fluid into cavity and wipe clean with clean cotton balls. Do not touch with fingers, dust on fingertips may scratch apolished surface. Be careful when blowing a cavity out, there may be dust or rust in the air lines which may damage the polished cavity. All components are checked for wear. Any excessive wear is noted and a determination is made to repair, replace or continue to use. All rough areas outside the cavity detail area are to be worked out. Any area insidethe cavity detail area with dings, dents or other signs of wear or abuse should beconsidered critical and should be carefully analyzed before replacements or repairs are commenced. All moving parts are to be lubricated if required. Use lubricant sparingly on all moving parts which make contact with plastic partsVents should be checked for depth, width and land as compared to the tool drawing specifications. This data should be recorded on the check list and a determinationmade to repair if required. They should also be checked for corrosion and vent burns “O” rings, seals and gaskets should be checked for integrity. All water lines are to be pressure tested for leaks and recertified for flow capacity.Water lines that have built up scale and are restricted should be pressure cleanedwith a descaling agent. The ejector system is to be examined for proper alignment. If the ejector pin holes have become egg shaped it must be determined if they should be redrilled and bored to a larger size and the existing pins replaced with over size pins. Broken return springs, replating or retexturing as a result of the material eroding the mold surface, replacement of gates or gate inserts, new runner blocks etc. must be analyzed and determined. Replace all springs after 50,000 cycles.

level 5. Major Maintenance

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 wherere 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.

Posted by Margaret

Company Name: Huangyan Zhilian Mould & Plastic Co.,Ltd
Website: http://www.zhilianmould.com



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