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How to control the color difference of products injected by high-speed precision injection molding machine

Jun 22, 2020

1. Eliminate the influence of high-speed precision injection molding machine and mold factors

    To choose an injection molding machine with the same capacity as the main product of the injection molding, if the injection molding machine has problems such as material dead angle, it is best to replace the equipment. For the color difference caused by the mold pouring system and the exhaust groove, it can be solved by the maintenance mold of the corresponding part of the mold. The problems of the injection molding machine and the mold must be solved before the production can be organized to reduce the complexity of the problem.


2. Eliminate the influence of raw resin and color masterbatch

    Controlling the raw materials is the key to completely solve the color difference. Therefore, especially when producing light-colored products, the obvious influence of the thermal stability of the raw resin on the color fluctuation of the product cannot be ignored. Since most injection molding manufacturers do not produce plastic masterbatches or masterbatches themselves, the focus of attention can be placed on production management and raw material inspection.


That is to strengthen the inspection of raw materials into the warehouse; the same product in production is produced using the same manufacturer, the same brand masterbatch, color masterbatch as far as possible; for color masterbatch, we must carry out random inspection and color test before mass production, both with the last proofreading, and In this comparison, if the color difference is not large, it can be considered as qualified, as if the batch masterbatch has a slight color difference, the color masterbatch can be 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 the manufacturer to exchange them.


3. Reduce the effect of barrel temperature on color difference

    In production, it is often encountered that a certain heating ring is damaged or fails, or the heating control part is out of control and burns, causing the barrel temperature to change drastically, resulting in color difference. The color difference caused by this kind of reason is easy to determine. Generally, the color difference caused by the failure of the heating ring is 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 during production, and replace and repair the heating part in time when it is found to be damaged or out of control, so as to reduce the probability of such color difference.


4. Reduce the impact of injection molding process adjustment

    When the injection molding process parameters need to be adjusted for non-color difference reasons, the injection temperature, back pressure, injection cycle, and the amount of color masterbatch should not be changed as much as possible. At the same time, the effect of the process parameter change on the color should also be observed. If the color difference is found, it should be adjusted in time. As far as possible, avoid the use of high injection speed, high back pressure and other injection molding processes that cause strong shearing to prevent color differences 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.


5. Master the influence of cylinder temperature and color masterbatch amount on product color change

    Before adjusting the color difference, you must also know the trend of the product color with temperature and the amount of color masterbatch. Different color masterbatch varies with the production temperature or the amount of color masterbatch. The change rule can be determined through the color test process. It is impossible to adjust the color difference quickly unless you already know the color law of this masterbatch.