How to deal with the color difference in the processing of injection products
Aug 06, 2021
Chromatic aberration is a common defect in injection molding, it will seriously affect the appearance of the product and may even cause loss due to chromatic aberration. There are many reasons for the formation of chromatic aberration, such as: the selection of plastic materials, the mixing method of color masterbatch, the injection molding process, and the rationality of mold design For various reasons, such as the operability of the personnel, the color difference control technology is recognized as one of the difficult technologies in injection molding. Today, let’s talk about how to deal with the color difference in the processing of injection molded products.
1. Machinery and equipment
When choosing an injection molding machine, you should consider an injection molding machine with the same capacity as the injection product. If the injection molding machine has problems such as material dead ends, the equipment must be replaced. The chromatic aberration caused by the mold gating system and the exhaust groove can be solved by the maintenance mold of the corresponding part of the mold. The injection molding machine and mold problems can be solved before the production can be made to reduce the complexity of the problem.
2. Selection of raw material masterbatch
Controlling raw materials is the key to solving chromatic aberration. Therefore, especially when producing light-colored products, the obvious influence of the different thermal stability of the raw material resin on the color fluctuation of the product cannot be ignored.
In view of the fact that most injection molding manufacturers do not produce plastic masterbatch or color masterbatch themselves, the focus of attention can be placed on production management and raw material inspection. That is to strengthen the inspection of raw materials storage; the same product in the production is produced by the same manufacturer, the same brand of masterbatch, and color masterbatches;
For the color masterbatch, we need to conduct random inspections before mass production. Both the same proofreading and comparison in this time. If the color is not much different, it can be considered qualified. Just as the batch of color masterbatch has a slight color difference, Use the color masterbatch after remixing to reduce the color difference caused by uneven mixing of the color masterbatch itself. At the same time, we also need to check the thermal stability of the raw resin and color masterbatch. For those with poor thermal stability, we recommend that the manufacturer replace them.
3. Color masterbatch mixing method
Poor mixing of plastic masterbatch and color masterbatch will also make the product color change impermanent. After the masterbatch and color masterbatch are mechanically mixed and sent into the hopper through the lower suction material, the color masterbatch is separated from the masterbatch due to static electricity and is easily adsorbed on the hopper wall. This will inevitably cause the amount of color masterbatch in the injection cycle to change, resulting in Chromatic aberration.
In this case, the raw materials can be sucked into the hopper and then manually stirred. For the production of colored products by adding toner, the effective way is not to use a suction machine, but to use a hot air dryer, and use manual feeding to prevent the color difference caused by separation of the toner from the master batch.
4. Standardized operation of personnel
In the production process, it is necessary to eliminate the undesirable errors caused by personnel errors, and check the key links, not let the novice control, and find the experienced master to assist in the completion.
5. Grasp the influence of the barrel temperature and the amount of color masterbatch on the color change of the product
Before adjusting the color difference, it is also necessary to know the trend of the product color with the temperature and the amount of color masterbatch. With the change of the production temperature or the amount of color masterbatch, the color change law of the product is different. The color test process can be used to determine its changing law.
Unless the color change law of this color masterbatch is known, it is impossible to adjust the color difference quickly, especially when using a new color masterbatch.
When the injection molding process parameters need to be adjusted for non-chromatic aberration reasons, try not to change the injection temperature, back pressure, injection cycle, and the amount of masterbatch added. At the same time, the adjustment also needs to observe the effect of the process parameter changes on the color. If the color aberration is found, it should be adjusted in time.
Avoid the use of injection molding processes that cause strong shearing effects such as high injection speed and high back pressure 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.
