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When maintaining the injection mold, how to clean it in place?

Update:02-09-2022
Summary:

Mold cleaning is a key process in mold maintenance, and […]

Mold cleaning is a key process in mold maintenance, and it is also a bottleneck restricting mold maintenance. Because the speed of mold manufacturing and development is much faster than the speed of mold cleaning, and the mold is ready for the next production immediately after the rapid cleaning, so the time left for mold cleaning is quite limited. Through the investigation of the factory, it was found that the molds arranged in the corridors and workshops in the workshop almost filled the limited operating space of the workshop, and were just waiting to be cleaned.

Some companies directly reset the mold without any cleaning after the end of a production, and continue to use it for reproduction. If the plastic part produced is clean, then there is no problem with the operation of the mold. Over time, a cultural concept of "temporary fire fighting" will form within the company. Only when the accumulated residues in the mold affect the quality of the parts or the mold is worn, the mold needs to be cleaned, and the cleaning process is only a pass. .

When cleaning and repairing the Helmet Mold, some factories will hire some junior mechanics or apprentices in the mold shop to do some chores of cleaning the mold and template, and then the mold and template will be disassembled by maintenance technicians. But in fact, cleaning the molds and stencils also washes away the track marks, making it difficult for service technicians to spot and properly repair defects in the molds and parts.

It's true that cleaning molds doesn't require the aptitude of an advanced mold maker, but it would be completely ill-advised to have a novice who is unfamiliar with the special features and defects of the mold or the characteristics of the critical sealing areas of the mold responsible for mold cleaning. Decide. Unreasonable distribution of mold cleaning work will result in continued production of molds with performance defects, and at the same time will greatly increase due to increased seams, burrs, corners, premature plating or steel shifting and mold mixing, etc. Mold budget. These types of problems often originate in a “fire-fighting” maintenance culture that never monitors or accounts for defects and pinpoints the source of the problem.

Standardized cleaning procedures

Systematic mold maintenance is based on the continuity of maintenance needs and maintenance operations. In order to achieve the goal of "cost-effectiveness", cleaning molds must pay attention: develop a detailed mold cleaning plan. When cleaning different parts of the mold, such as internal cleaning of the press, wiping along the edge, conventional cleaning, and main part cleaning, the cleaning operation methods used are also different.

After the mold has run for a certain period of time and has undergone visual testing of electroplating wear, track marks, and mold residue content in vented and non-vented areas, technicians can determine the program and frequency of mold cleaning through visual inspection. Therefore, it is very important to understand the cycle of safe operation of the mold and to document the observation reports of the accumulation of residues and wear inside the mold.

Since molds have a certain operating cycle, all molds should be accompanied by relevant maintenance procedures and documentation of maintenance cycles. In general, controlling internal grease levels and the operation of gear broaching, sliders, internal shaft pins and bushings, and other moving parts is key to ensuring stable production. Other factors that affect production include contamination or blockage of water lines and sprinkler drinking ports, leaking manifolds, rust and corrosion due to water leaks or condensation.

How much cleaning is enough?

Usually, when the molding process operation is completed, dirt or residue (with certain chemical composition and physical characteristics) tends to be left on the mold. For different types of residues, cleaning requirements are also different. Resins like polyvinyl chloride produce hydrogen chloride gas that corrodes many types of die steel.

Other residues are separated from flame retardants and antioxidants and can corrode the steel. There are also pigment colorants that can rust steel, and the rust can be difficult to remove. Even ordinary sequestered water can cause damage to the mold if left on the untreated mold surface for too long.

Therefore, the necessary cleaning of the mold should be carried out according to the established production cycle. Every time a mold is removed from the press, the mold blowholes first need to be opened to remove all oxidized dirt and rust from non-critical areas of the mold and formwork to prevent it from slowly corroding steel surfaces and edges. In many cases, some uncoated or rust-prone mold surfaces quickly reappear with rust, even after cleaning. Therefore, even if it takes a long time to brush an unprotected mold, surface rust cannot be completely avoided.

Many molds now feature "self-cleaning" vent lines that have a high gloss finish. Prevent residues from adhering to the surface of the roughing stand by cleaning and polishing the vent holes to a SPI#A3 finish, or by milling or grinding and discharging the residue to the trash area of ​​the vent line . However, excessive "cleaning" of the mold occurs when the operator manually grinds the mold with coarse-grained scrubbing pads, emery cloth, sandpaper, grindstones, or brushes with nylon bristles, brass, or steel.

Generally, when using hard plastics, glass beads, walnut shells and aluminum pellets as abrasives for high-pressure grinding and cleaning of the mold surface, if these abrasives are used too frequently or improperly used, this grinding method will also make the mold. Pores are generated on the surface and residues are easily attached to it, resulting in more residues, wear, or premature mold breakage or burrs, which is even more unfavorable for mold cleaning.

Therefore, by looking for cleaning equipment suitable for the mold and processing technology, and referring to the cleaning method and cleaning cycle recorded in the archived documents at the same time, more than 50% of the maintenance time can be saved, and the wear of the mold can be effectively reduced.

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