When the production is over or the quality of injection molding fails, the injection molding machine needs to be shut down temporarily or for a long time. How to do the shutdown work is not only related to the quality of the next molding and the loss of raw materials, but also affects the service life of the screw and barrel.
Just before the molding is completed or before the temporary stop, empty the barrel-like materials, and then add an appropriate amount of cleaning material to clean the barrel, press the heating switch to turn off the barrel electric heating. Close the hopper baffle. If it is a temporary short-term shutdown, do not turn off the electric heating of the barrel, and reduce the heating temperature by 100 to 150 degrees per section.
If the injection molding machine is equipped with a temperature regulator for nozzle temperature adjustment, turn the regulator button to 0 to disconnect the regulator. This is not only to be able to heat the feeding cylinder in the shortest possible time during the next injection molding operation. In order to prevent the melted resin from staying in the barrel, the remaining material in the heating barrel should be completely removed (inject several times in the air), and then an appropriate amount of cleaning material should be added to clean the barrel, and finally the screw should be stopped at the forefront position.
In the manual state, close the mold (but do not enter the high-pressure clamping), and return the injection seat and the screw to the stop position. Turn off the oil pump motor and pay attention to the total power supply of the injection molding machine. 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 frequency of spray cleaning will increase. When performing minor repairs; the heater of the injection cylinder must be adjusted to the lowest value, such as 150°C, to minimize the possibility of thermal decomposition.
For plastic machining, if it has been shut down for one night in advance, just 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 cleaned. 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 sliding plate at the bottom of the hopper, and try to spray the oblique rubber in the barrel again. If there is no more plastic spray, the equipment can be closed for the next use.
If the machining uhmw decomposes or burns in the injection molding machine, it will eventually change color and make 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 thermally stable plastic 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, it is best to use natural, non-fire-resistant grades of PS or PE as the spray cleaner; if the leftover material is not completely sprayed, please do not mix POM with PVC, or mix them in sequence.
Before shutting down or switching to another plastic, you must check that the steps taken are correct. The manufacturer of cnc turning service has printed a booklet with sufficient information. Please read it carefully before operation to understand the “standard shutdown procedure” required for each type of plastic. The brochure should be placed next to the injection molding machine so that the operator can read it at any time.