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How to control the color difference of products in the process of plastic mold processing

Update:20-01-2022
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The color difference of products in plastic mold proces […]

The color difference of products in plastic mold processing plants is a common defect in injection molding. It is not uncommon for injection molding machines to be scrapped in batches due to the different colors of matching parts. There are many factors that affect color difference, including the mixing of raw resin, color masterbatch, color masterbatch, and homogeneous materials. Injection molding products, injection molding machines, molds, etc., because of the extensive involvement, the chromatic aberration control skills are also recognized as one of the difficult skills to master in injection molding. Next, I will introduce them in detail.
1. Eliminate the influence of injection molding machines and mold elements
It is necessary to select an injection molding machine with an appropriate capacity for the main product of plastic mold processing, assuming that there are problems such as material dead ends in the injection molding machine, and replace the equipment. The color difference caused by the mold casting system, exhaust grooves, etc. can be dealt with by the repaired mold of the corresponding part of the mold. It is necessary to first deal with the injection molding machine and the mold head to be able to organize production to reduce the complexity of the problem.
Eliminating the influence of raw resins and color masterbatches and controlling raw materials is the key to dealing with chromatic aberration. Therefore, especially when producing light-colored products, the significant impact of different thermal stability of raw resins on product stability cannot be ignored. In view of most injection molding production, The manufacturers themselves do not produce plastic masterbatches or color masterbatches. In this way, the focus of attention can be placed on production management and raw material inspection. That is to strengthen the inspection of raw materials entering the warehouse; the same product in production should use the same manufacturer and the same trademark masterbatch as much as possible. , production of color masterbatches; for color masterbatches, we need to conduct random inspections and test colors before mass production, which is not only corrected with the previous one, but also compared in this time. If the color difference is not big, it can be qualified, as if the batch color The masterbatch has a slight color difference, and the masterbatch can be re-mixed and then used to reduce the color difference caused by the uneven mixing of the masterbatch itself. At the same time, we also need to check the thermal stability of the raw resin and color masterbatch. , we recommend that manufacturers exchange.
2. Eliminate the influence of uneven mixing of color masterbatch and masterbatch
Poor mixing of the plastic masterbatch with the color masterbatch will also cause the color of the product to change. Wall, which will inevitably lead to changes in the amount of color masterbatch in the injection cycle, and then color difference. In this case, the material can be sucked into the hopper and then mixed manually. Now many companies use feeders to add color. This saves a lot of manpower and provides great assistance for color difference control. However, due to improper use by many companies, the results are often unsatisfactory. The amount of color masterbatch added by the feeder at a fixed speed depends on the plasticization. time and the plasticizing time itself is fluctuating, sometimes even relatively large, so to ensure a stable feeding amount, the feeding time of the feeder needs to be fixed, and the setting time is less than the plasticizing time. When using the feeder It is necessary to pay attention when feeding, because the outlet of the feeder is small, after a period of use, the material powder accumulated in the screw of the feeder may be blocked from feeding, or even the feeder will stop, so it needs to be sorted out regularly.
3. Reduce the influence of barrel temperature on chromatic aberration
In the production of plastic mold processing plants, it is often encountered that the temperature of the barrel changes drastically due to the failure of a heating ring or the uncontrolled long-burning of the heating control part. The occurrence of chromatic aberration 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 during production and find that the heating part is damaged or out of control. Replace and repair to reduce the chance of such chromatic aberration.
4. Reduce the influence of injection molding process adjustment
When the injection molding process parameters need to be adjusted for reasons other than a 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, the influence of the process parameter changes on the product should be investigated. If chromatic aberration is found, it should be adjusted in time. As far as possible, avoid the use of high injection speed, high backpressure, and other injection molding processes that cause strong shearing effects, and avoid chromatic aberration caused by some factors such as overheating or thermal differentiation. Strictly control the temperature of each heating section of the barrel, especially the nozzle and the nozzle close to the nozzle. the heating part.
5. Master the influence of barrel temperature and color masterbatch on product color change
Before making color difference adjustment, it is also necessary to know the trend of product color change with temperature and color masterbatch. Different color masterbatches change with production temperature or color masterbatch, and the rules for product color change are different. It can be obtained through the color test process. Confirm the change rules. Unless you know the change rules for this master color, it is impossible to adjust the color difference quickly, especially when using the color produced by the new master color.