Injection Molding Machine Operation Specification for Changing Plastic or Color

Every production part of the injection molding  machine is very indispensable including the the part of changing plastic materials. Therefore, in this post, we’re going to make clear the operation specification for changing plastic or color.

1. Plastic characteristics and precautions for shutdown

The characteristics of various plastic raw materials are different. When shutting down the machine, the characteristics of the rubber material should be considered. And that can save time and avoid plastic deterioration.

According to the characteristics of different plastics, the following methods are given:

(1) PS & ABS

PS and ABS are hard glues with good thermal stability. They will not decompose even if they are heated for a long time at the molding temperature. Therefore, it is only necessary to turn off the electric heater to stop the machine.

(2) PE & PP

PE and PP are soft rubber with good thermal stability, and they will not decompose when heated for a long time at the molding temperature. Therefore, we only need to turn off the electric heater to stop the machine.

(3) PC

Due to the temporary suspension of production (such as not starting the night shift), it is necessary to keep the barrel at about 160°C to prevent the rubber from getting wet. When changing the material, it is necessary to clean the barrel with PE, take out the screw, and clean the screw with a copper brush.

Operation Specification for Changing Plastic or Color (1)

(4) PVC

PVC is a heat-sensitive material. Turn off the electric heater before stopping the machine, then push out the PVC until the temperature of the barrel drops to 150°C. And finally use PP, PE and other plastics with good thermal stability to push out all the plastic in the barrel.

(5) PMMA

PMMA is easy to decompose at higher temperature, but its thermal stability is still good at normal molding temperature. So it is only necessary to turn off the electric heating when shutting down.

(6) PA

Nylon PA is a plastic with good thermal stability. Do not clean the barrel before stopping the machine, but turn off the power immediately. Otherwise the plastic will deteriorate after 15 minutes.

(7) POM

POM is a heat-sensitive plastic. When the machine is shut down, the pressure should be lowered 10 minutes before the electric heating is turned off. And then the plastic in the barrel should be pushed out continuously. When changing the material, it should be cleaned with soft rubber first.

2. Color change of the same material

When changing the color of the same material, change the material from light color to dark color, and from transparent to opaque as possible.

When changing the material from thick color to light color, or from opaque to transparent, if the color is still not pure after more than ten times of empty injection, remove the nozzle and cylinder head for cleaning.

Operation Specification for Changing Plastic or Color (2)

3. Replacement of different materials

Thermoplastics will stick to the metal surface when the temperature is high, and will not stick when the temperature is low. The replacement operation is to use this property of the material to make the material to be replaced stick to the inner wall of the barrel. Then, the material with high viscosity (replacement material) is supplied and rotated by the cold screw to remove the material to be extruded.

4. Replace plastic material and color at the same time

In this case, a plastic with similar characteristics should be selected and used together with a cleaning agent. General cleaning agents are: screw cleaning agent, kerosene, etc.

If the barrel is not cleaned in this case, please remove the nozzle and clean the head of the barrel. If necessary, remove the screw for cleaning.

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