Black spot is a common problem in the use of three screw pelletizer. It should be solved in this way.

In the process of pumping, it is a common problem to encounter the black spots of the fine particles, and how to teach you how to deal with the black spot during the granulation of the three screw granulator is the focus of this chapter, and this phenomenon is the problem of the three screw granulator, the problem of raw materials, or the others. What does the factor lead to? The following will answer the doubts in the heart! The appearance of black spot in the granulation process of three screw granulator is a common failure phenomenon, especially in color and light color products, especially in the final production process, it is found that the product performance and the feeling product color are all right, but after the period of time, the customer complaint "product fits". The rate is too low, there are black spots, asking for returns "and so on, and this time entangled in the question of why there will be black spots, many friends have a headache.

Of course, such a situation is really very annoying. But there are a lot of black spots, filler can have, raw materials can have, raw materials are not, but after the carbonization in the screw, there are many outside dust will also have; carbon powder dispersion will also cause black spots and so on, so specific problems should be specific analysis! In the actual production of plastic products, the intake port is generally isolated before the shutdown, the three screw granulator and the plastic melt in the head of the machine are excluded, the temperature of each area is closed, and then the power supply is closed. Because the plastic melt has strong adhesion to the metal, it is impossible to completely eliminate it at a time of stopping. Finally, there will always be a thin layer of plastic melt firmly attached to the extruder's barrel and the inner wall of the machine head and the screw. After the shutdown, the equipment is cooled and cooled for a long time in the process of high temperature. Retention, obvious thermal deterioration, gradually yellow and zoom into carbide. In accordance with the conventional stopping method, no effective sealing measures are taken at both ends of the head and the inlet of the feeding port. The air enters the machine to produce oxidation, and the residual plastic heat deterioration in the three screw granulator machine is aggravated, and the favorable conditions for carbonization are provided. Because the equipment is a metal structure, the thermal expansion rate of the plastic is different from that of the plastic. The adhesiveness of the carbonized plastic is reduced to the metal. It is easy to fall off the inner wall of the machine barrel, the inner wall of the machine and the screw. It is mixed into the plastic melt, which causes many black spots on the inside and outside wall of the products, and it is easy to present many quality problems, such as holes or leakage, etc. After a long time of shutdown, heating and reopening the machine, plastic products easy to appear a lot of large and small black spots, can not meet the quality requirements of the products, these black spots are the residual plastic in the machine after the carbide. Usually, it is necessary to use plastic continuous extrusion to remove the plastic melt with black spots to clean the machine and wash the machine for up to 3-5 hours. If the original ultra high molecular weight plastics are carbonized and produce the original color products, the difficulty of the washing machine will be greatly increased, and the washing time will be longer and the cost of the washing machine is higher.

To quickly clean the carbide inside the machine, we need to use some hard plastic material or its return material and white mineral oil to wash it, and the temperature is raised 10~15 degrees. At this point, the plasticizing capacity of the small extruder should be considered. Large and medium extruders that can plasticized ultra-high molecular weight plastics can be washed with ultra-high molecular weight plastics or their recycled materials and white mineral oil. Because the hardness of the super high molecular weight plastic is better and the temperature is high, the cleaning object will be softened, so it becomes easy to fall off, and it is good for the carbide to be taken out of the plastic melt. During the cleaning process, the speed of the extruder is repeatedly switched between low speed and high speed. If there is a residual load on the motor, it can repeatedly stop and restart the extruder several times during the operation so as to further improve the cleaning effect. When the carbide (black spots) in the melt is obviously reduced, the replacement of the usual plastic is cleaned until it is cleaned, and it is gradually adjusted to the appropriate temperature, then it can be produced normally.

In order to avoid the harm of carbonization to plastic products as far as possible, the key is to prevent effectively and minimize losses. To understand the essence of carbonization, we should also be good at using effective solutions. We need to strictly control every link in the solution and prevention of carbonization of plastic products. This is an effective way. And the experience of this point is more important, and the accumulation of experience can be analyzed through the accumulation of practice and the case on the books and network data, which can be called the accumulation of theoretical experience. Of course, in this process, there is no doubt that there is a certain amount of time. But quantitative change is bound to cause qualitative change. It is only a matter of time.