Injection molding mold cleaning requirements

Time:2019-09-06 13:59:00 / Popularity: / Source:

Injection molding tool are the most important molding equipment for products made by injection moulding, and their quality is directly related to quality of products. Moreover, since mold occupies a large proportion in production cost of plastic injection molding factory, its service life directly affects cost of products made by injection moulding. Therefore, by improving quality of injection molding manufacturing process, maintaining it, and extending its life cycle, more products can be produced.
Injection molding mold 
Mold cleaning is a key process in mold maintenance, and is also a bottleneck restricting mold maintenance.
Injection molding tool is one of main equipments for injection molding manufacturing process. Therefore, mold inspection and maintenance methods are developed to effectively maintain mold precision and stabilize production operations, ensure quality of products made by injection moulding, reduce occurrence of failures in production process, and ensure normal production of mold in injection molding manufacturing process workshop, reduce mold failure and product quality issues, so that mold can maintain the best performance state and prolong life to ensure normal production.
Due to variety of products and frequent replacement of molds, after plastic injection molding factory completes a production cycle, molds are generally stored in warehouse until next production cycle comes out. However, some plastic injection molding factory pay insufficient attention to preservation of molds, causing rust and surface roughness during storage period, resulting in a decline in product quality and high scrap rate. Some injection molding mold are even difficult to reuse, and it is necessary to reinvest a large amount of money to set up a new mold, resulting in great waste.

Standardized cleaning procedure

Systematic mold maintenance is based on consistency of maintenance requirements and maintenance operations. In order to achieve "cost-effective" goal, cleaning molds must be careful: develop a detailed mold cleaning program. When cleaning different parts of mold, such as internal cleaning of press, wiping along edge, regular cleaning, and main cleaning, cleaning operation method is also different.
After a certain period of operation of injection molding tool and after visual inspection of plating wear, track marks, and mold residue content in venting and non-venting areas, technician can determine procedure and frequency of mold cleaning by visual inspection. Therefore, it is important to understand cycle of safe operation of mold and to document observations of residual residue and wear in mold.
Based on mold having a certain operating cycle, all molds should be accompanied by documentation of relevant maintenance procedures and maintenance intervals. In general, controlling internal grease level, operation of gear broaching, sliders, internal shaft pins and bushings, and other moving parts is key to ensuring stable production. Other factors affecting production include contamination, blockage of waterline and sprinklers, leakage of manifolds, rust and corrosion due to water leakage or condensation.

What level of cleaning is OK?

Injection molding mold 
Usually when injection molding manufacturing process is completed, it tends to leave dirt or residue on mold (having certain chemical composition and physical properties). Final cleaning requirements are different for different types of residues. Resins such as polyvinyl chloride produce hydrogen chloride gas, which can corrode many types of die steel. Some other residues are separated from flame retardant and antioxidant, which can cause corrosion to steel. There are also some pigment colorants that can rust steel and rust is difficult to remove. Even ordinary sealed water, if placed on surface of an untreated mold for a long time, will also cause damage to mold.
Therefore, injection molding tool should be cleaned as necessary according to established production cycle. Each time mold is removed from press, it is first necessary to open mold vents to remove all oxidizing dirt, rust from mold and non-critical areas of stencil to prevent it from slowly corroding steel surface and edges. In many cases, even if cleaning is completed, some uncoated or rust-prone mold surfaces will soon appear rust again. Therefore, even if it takes a long time to brush unprotected mold, surface rust cannot be completely avoided.
Many injection molding tool now have "self-cleaning" vent lines that have a high gloss. By rinsing and polishing vents to degree of polishing of SPI#A3, or by milling or grinding, residue is discharged to waste area of vent line to prevent residue from adhering to surface of roughing stand. However, if operator uses a coarse brushing pad, emery cloth, sandpaper, grindstone or a brush with nylon bristles, brass or steel to manually grind mold, it will cause excessive "cleaning" of mold.
Generally, when hard plastic, glass beads, walnut shells, and aluminum pellets are used as abrasives to perform high-pressure pulverization cleaning on surface of mold, if abrasive is used too frequently or improperly used, this grinding method also create voids on surface of mold and tend to adhere to residue, resulting in more residue, wear, or premature rupture or burrs of mold, which is more detrimental to mold cleaning.
A well-maintained mold can shorten mold assembly, test time, reduce production failures, stabilize production, ensure product quality, reduce waste loss, and reduce operating costs and fixed asset investment. When the next production cycle begins, plastic injection molding factory was able to produce quality products. Therefore, for plastic injection molding factory, in current fierce market competition, maintenance of good molds can help enterprise.

Go To Top