The production of high-quality parts is indeed daily business for the plastics processing industry. In production, it is not uncommon to fall back on the moulds of the customers. It is indispensable to treat the tools provided with care, because if damages occur, the reputation of the processing company naturally suffers. But that’s not all: competitive pressure is also forcing thermoplastics processors to achieve maximum efficiency and constantly rising quality standards.
During thermoplastic processing, small amounts of the polymer, additives and pigments usually remain on the surface. Over time, this leads to deposits that also affect the surface quality of the parts. This threatens an increase in rejects – and creates a clear economic risk. In fact, just a few defective parts can affect an entire batch.
If such a batch is nevertheless delivered, there is a risk of consequences such as complaints or a poorer supplier rating. And in its worst case, the customer relationship is in jeopardy. The formation of such residues is a slow and steady process that is by no means always synchronous. For example, certain polymers, additives and pigments have a greater tendency to form deposits during long production cycles, others less so. Polyamides, PVC, acetals and numerous other substances, for example, accumulate more, polyolefins leave wax and trapped pigments on cavity surfaces.
How To Proceed With Maintenance?
The question of how to proceed with maintenance is by no means trivial. The differences in quality only become apparent in the final analysis. In order to reduce the unavoidable and often considerable maintenance costs and downtimes, the regular use of mould cleaners is recommended. The advantage is that plastics processors can save a lot of money, time and waste with a small amount of material and only a few minutes for regular cleaning.
What is particularly important to look out for? Checking for weld lines, bubbles and surface defects is still comparatively simple. This can be done directly at the machine and in a timely manner. Partially blocked vents (such as vent pins) can be much more difficult to detect. But they are very important in the process, because contaminated mould parts and tools can significantly impair filling. A good indication is also when an increasing surface gloss appears on structured surfaces – but this is often difficult to detect.
Source: Laurent Saleur (Chem-Trend) in the trade journal Plastverarbeiter 9/2021
Photo: Всеволод Чуванов