Attention should be paid when the injection molding machine is shut down

- 2021-07-03-

If the injection molding machine is suspended, the remaining plastic must be sprayed out or let the plastic pass through the injection molding machine to clean the remaining plastic in the injection cylinder or barrel. In case of plastic fading, the number of blow-outs will increase. For minor repairs; the heater of the injection cylinder must be adjusted to the maximum value, such as 150°C, to minimize the possibility of thermal decomposition.

Before injecting thermally stable plastics (such as PS or PE), if you have shut down for one night in advance, you only need to turn off the sliding plate at the bottom of the hopper and the heater of the injection cylinder (only the heater of the nozzle is turned on), and the injection cylinder is blown out clean. After the nozzle is completely cleaned, cool the barrel as high as possible. After the injection molding machine has cooled down, turn off all equipment. The injection molding machine is fully ready to reheat.
If the temperature of the injection cylinder or barrel is high, only slightly modify the above steps to prevent the resin from being decomposed by heat. For example, turn off the heater of the injection cylinder (only turn on the heater of the nozzle), or cool the barrel as high as possible, during which the remaining resin is continuously sprayed out. Close the slide plate at the bottom of the hopper, and try to spray the oblique rubber in the barrel again. If no more plastic is sprayed, the equipment can be closed for the next use.

If the plastic decomposes or burns in the injection molding machine, it will eventually change color, making the finished product waste. In this case, the injection molding machine must be completely shut down and spray clean. The prevention method is to use a plastic with higher thermal stability to blast out the heat-sensitive resin so that it can withstand subsequent reheating.
Some plastics (such as POM, PVC) are easy to decompose. If the machine stops suddenly during injection molding, the heater of the nozzle should be turned on before the injection is continued. Only when the plastic has the nozzle melted, can the heater of the injection cylinder be turned on. The temperature of the shooting cylinder or barrel should be adjusted to about 140°C. Then raise the temperature to the processing temperature, and spray the remaining plastic as soon as possible. The sprayed plastic must be put into cold water. If you want to change other plastics, use PS or PE natural, non-fireproof grades as the cleaning agent; if the remaining material is not completely sprayed, please do not mix POM with PVC, or mix them one after another.

Before stopping the machine or switching to another type of plastic, check that the steps taken are correct. The material supplier has already printed and prepared a booklet with sufficient information. Read it carefully before operation to understand the "standard shutdown procedure" required for each plastic. The brochure should be placed next to the injection molding machine so that the operator can read it at any time.