Color difference of plastic products is a common defect in injection molding. There are numerous factors that affect color difference, such as raw resin, masterbatch, mixing of color masterbatch and raw materials, injection molding process, injection molding machine, etc. Injection moulding processing manufacturers generally control the color difference from the following five aspects in the actual production process.
It is necessary to choose an injection molding machine with the same capacity as the injection molding products. If the injection molding machine has problems such as material dead ends, it is best to replace the equipment. The chromatic aberration caused by the mold gating system, exhaust groove, etc., it can be solved by the maintenance of the corresponding part of the plastic mold by injection molding accessories suppliers. The problem of injection molding machines and mold must be solved first before production can be organized to reduce the complexity of the problem.
Controlling injection moulding raw material list is the key to completely solving chromatic aberration. Therefore, especially in the production of light-colored products, the obvious influence of the thermal stability of the raw resin on the color fluctuation of injection molding products cannot be ignored. Given that most injection molding manufacturers do not produce plastic masterbatches or color masterbatches themselves, the focus can therefore be placed on production management and raw material inspection.
That is to strengthen the inspection of raw material storage. In production, the same product should be produced by the same manufacturer, the same brand masterbatch and color masterbatch as much as possible. For the color masterbatch, we need to conduct random inspection and test color before mass production. It is not only necessary to proofread with the last time, but also to be compared in this time. If the color difference is not large, it can be considered qualified. Just like the batch color masterbatch has a slight color difference, it can be The color masterbatch is re-mixed before use to reduce the color difference caused by the uneven mixing of the color masterbatch itself. At the same time, we also need to focus on testing the thermal stability of the raw resin and color masterbatch. For those with poor thermal stability, we recommend that the manufacturer replace them.
In production, injection moulding supplies are often encountered that a heating ring is damaged and failed, or the heating control part is out of control and the temperature of the barrel changes drastically, resulting in chromatic aberration. The color difference caused by such reasons is easy to determine. Generally, the color difference caused by the failure of the heating ring will be accompanied by uneven plasticization, and the uncontrolled long burning of the heating control part is often accompanied by product gas spots, severe discoloration, and even coking. Therefore, it is necessary to check the heating part frequently in production and replace and repair it in time when it is found that the heating part is damaged or out of control, so as to reduce the probability of such chromatic aberration.
When it is not necessary to adjust the injection process parameters due to non-chromatic aberration, the injection temperature, back pressure, injection cycle and the amount of color masterbatch added should not be changed as much as possible. At the same time, it is necessary to observe the influence of process parameter changes on the color. If the color difference of injection molding products is found, it should be adjusted in time. Avoid using high injection speed, high back pressure, and other injection molding processes that cause strong shearing effects as much as possible to prevent color difference caused by local overheating or thermal decomposition. Strictly control the temperature of each heating section of the barrel, especially the nozzle and the heating part close to the nozzle.
Before adjusting the color difference, it is also necessary to know the trend of the product color changing with temperature and color masterbatch. Different color masterbatches change with the production temperature or color masterbatch amount, and the color change rules of automotive plastic injection molding products are different. The change rule can be determined through the color test process. It is impossible to quickly adjust the color difference unless the color change law of the masterbatch is known.