If the plastic barrel manufacturer needs to change the plastic variety, material, or color during production, or if thermal decomposition or degradation occurs during the molding process, the barrel of the injection machine should be cleaned. Usually, the plunger injection machine has a large barrel, which must be disassembled and washed. For screw-type barrels, air injection can be used for cleaning.
When using the air-injection method to clean the screw-type barrel, if the molding temperature of the plastic to be replaced is lower than the molding temperature of the residual material in the barrel, the temperature of the barrel and the nozzle should be raised to the maximum molding temperature of the plastic to be replaced. Turn off the power and add the return material of the plastic to be changed, and continue to inject air until all the residual material is eliminated; if the molding temperature of the plastic replaced by the plastic barrel manufacturer is higher than the molding temperature of the residual material in the barrel, the barrel should be And the nozzle temperature rises to the minimum molding temperature of the plastic to be changed, then adds the plastic to be changed or its return material and continuously injects into the air until all the residual material is eliminated.
If the temperature difference between the two plastic molding temperatures of the plastic barrel manufacturer is not large, it is not necessary to change the temperature, and the material can be injected by air first and then the plastic to be changed. When the residual material is a heat-sensitive plastic, a grade with a relatively high viscosity should be selected from the plastics such as polyethylene and polystyrene with good fluidity and thermal stability as the transition material for air injection.
For plastic parts with inserts, due to the different shrinkage rates of metal and plastic, the plastic around the insert is prone to shrink stress and cracks. Therefore, pre-heat the insert before molding to reduce its melt with plastic during molding. Temperature difference to avoid or suppress shrinkage stress and cracks in the plastic surrounding the insert. When the insert is small, plastics that are flexible to the molecular chain may not be preheated.https://www.fhpails.com/