How to clean injection molds properly when maintaining them?

Mold cleaning is a key process in mold maintenance and a bottleneck that restricts mold maintenance. Because the speed of mold manufacturing and development is much faster than the speed of mold cleaning, and after rapid mold cleaning, it is necessary to prepare for the next production immediately, 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 almost occupy the limited operating space of the workshop, waiting for cleaning.

Some companies directly reset the mold after the first production without any cleaning treatment and continue to use it for reproduction. If the plastic parts produced are clean, it indicates that the mold is running smoothly. Over time, a cultural concept of "temporary firefighting" will emerge within the company. Only when the accumulated residue in the mold affects the quality of the parts or the wear of the mold, it is necessary to clean the mold, and the cleaning process is only a passing process.

Some factories hire junior technicians or apprentices from the mold workshop to do miscellaneous tasks such as cleaning and repairing molds, and then the maintenance technicians will separate the molds and templates. But in fact, when cleaning molds and templates, the traces will be washed away, making it difficult for maintenance technicians to detect and correct defects in molds and parts.

Admittedly, cleaning molds does not require the talent of a senior mold manufacturer, but it is completely thoughtless to have a novice who is not familiar with the special functions and defects of molds or the characteristics of key sealing areas of molds responsible for mold cleaning work. Unreasonable allocation of mold cleaning work can lead to continuous production of molds with performance defects, and the addition of seams, burrs, edges, premature electroplating or steel displacement, mixing, etc. can also greatly increase the budget of the mold. This type of problem often stems from the maintenance culture of "temporary firefighting", which never monitors or accounts for defects, nor identifies the root cause of the problem.

The mold maintenance of the system is based on maintenance requirements and continuity of maintenance operations. In order to achieve the goal of "cost-effectiveness", it is necessary to pay attention to developing a detailed mold cleaning plan. When cleaning different parts of the mold, such as internal cleaning of the press, edge cleaning, routine cleaning, and cleaning of the main parts, different cleaning methods are used.

After the mold has been running for a certain period of time, technicians can determine the cleaning procedure and frequency of the mold through visual inspection of electroplating wear, magnetic marks, and residual content in the exhaust and non exhaust areas of the mold. Therefore, it is very important to understand the safe operation cycle of the mold and archive observation reports on residual accumulation and wear inside the mold.

Due to the certain operating cycle of molds, all molds should be accompanied by relevant maintenance procedures and maintenance cycle documents. Generally speaking, controlling the internal grease level and the operating conditions of moving components such as pullers, sliders, inner shaft pins, and bushings is the key to ensuring stable production. Other factors that affect production include pollution or blockage of water lines and nozzles, leakage of manifolds, rust and corrosion caused by water leakage or condensation, etc. What level of cleanliness is sufficient?

Usually, after the completion of the molding process, dirt or residue (with certain chemical composition and physical properties) will be left on the mold. The requirements for cleaning vary depending on the type of residue. PVC and other resins can produce hydrogen chloride gas, which can corrode various types of mold steel.

Other residues are separated from flame retardants and antioxidants, which can corrode steel. Some pigments and colorants can rust steel, and rust is difficult to remove. Even ordinary sealing water can cause damage to the mold if left on the surface of the untreated mold for too long.

So the mold needs to be cleaned according to the established production cycle. Every time the mold is removed from the press, the first step is to open the pores of the mold and remove all oxidation dirt and rust from the non critical areas of the mold and template to prevent them from slowly corroding the steel surface and edges. In many cases, even after cleaning, some uncoated or rusted mold surfaces will quickly rust again. So, even if it takes a long time to brush unprotected molds, surface rust cannot be completely avoided.

Nowadays, many molds have "self-cleaning" vent pipes with high glossiness. Clean and polish the exhaust hole to the polishing level of SPI # A3, or discharge the residue into the waste area of the exhaust pipe through milling or grinding to prevent the residue from adhering to the surface of the rough rolling frame. However, if the operator manually rubs the mold with coarse scrubbing pads, sandcloth, sandpaper, grinding stones or nylon bristles, brass or steel brushes, it will cause excessive "cleaning" of the mold.

Generally, hard plastics, glass bead, walnut shells, aluminum balls, etc. are used as abrasives for high-pressure grinding and cleaning of mold surface. If these abrasives are used too frequently or improperly, this grinding method will also cause pores on the mold surface, resulting in more mold residues, wear or premature damage or burrs, which is not conducive to mold cleaning.

Therefore, by searching for suitable cleaning equipment for molds and processing processes, and referring to the cleaning methods and cycles recorded in the archived documents, more than 50% of the maintenance time can be saved, effectively reducing mold wear and tear.