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Material Changing Reference
 

When plastic injection molding machine is in operation sometime it must change the plastic material and color to save the time and expenditure.

  1. For the same plastic material but change of color.
    When the same plastic material is used but to change is color, it is a simplicity if bright color is change to dark color or transparent color change to translucent color. Steps for changing material color as below:
    1. Close the stopper plate at the hopper dryer.
    2. Injection a few times until the material inside the barrel is clear.
    3. Input the new material into the hopper dryer.
    4. Open the stopper plate then inject and change the new plastic material until it change the plastic material color fully.

    For the translucent color change to transparent color it usually have to take out the nozzle head, if necessary injection screw will be take out to be clean.

  1. For the different plastic material change color.
    For the different plastic material change color, it is used by different material melting viscosity and the barrel temperature to control change color. For thermoplastic material, when the material temperature is low the plastic material cannot stick to the metal surface. From this theory, we use the high viscosity plastic material (example: HDPE or PS) take out the plastic material we want to change.
    1. Before finish changing plastic material, the barrel temperature should be lower than the actual temperature, example the low temperature melting material "A" change to high temperature melting material "B," the temperature of material "B" should be lower 10°C - 20°C simultaneity than it’s temperature. The high temperature melting material "B" change to low temperature melting material "A," the temperature of material "A" should be lower 10°C - 20°C than it’s temperature.
    2. The screw revolution speed must be adjust slowly and decrease back pressure of screw to prevent the plastic material from friction thus making the temperature rise.
    3. For the basic material in the barrel avoid to stick at surface screw injection.
    4. At short stroke use to fast speed inject the material and charging a few times.
    5. If the surface of the barrel or screw injection is cracked or damaged the melting material will stick at the cracked area so the material is hard to clean it.
  1. Inject to change the plastic material.
For PC as the raw plastic material
(1) PC change to ABS
  1. Inject all PC material in the barrel.
  2. Set temperature of PC material then use HDPE to clean out PC.
  3. Decrease the barrel temperature below 220°C then use ABS to clean out the HDHE.
(2) PC change to POM
  1. Inject all PC material in the barrel.
  2. Set the temperature of PC material then use HDPE to clean out PC.
  3. Decrease the barrel temperature below 190°C then use POM to clean out the HDPE.
(3) PC change to PMMA
  1. Inject all PC material in the barrel.
  2. Set the temperature of PC material then use HDPE to clean out PC.
  3. Decrease the barrel temperature below 240°C, then use wet PMMA to clean out the HDPE and used the dry PMMA to clean out the wet PMMA again.
(4) PC change to PP
  1. Inject all PC material in the barrel.
  2. Set the temperature of PC material then use PP to clean out PC.
  3. Decrease the barrel temperature until 200°C then inject out the PC material until it is clean.
(5) PC change to HIPS
  1. Inject all PC material in the barrel.
  2. Set the temperature of PC material then use HDPE to clean out PC.
  3. Decrease the barrel temperature below 220°C then use HIPS to clean out the HDPE.
For ABS as the raw plastic material
(1) ABS change to PC
  1. Inject all ABS material from the barrel.
  2. Set the temperature of ABS material then use PE to clean out ABS.
  3. Increase the barrel temperature until 290°C then use PC to clean PE.
(2) ABS change to POM
  1. Inject all ABS material in the barrel.
  2. Set the temperature of ABS material then use PS to clean out ABS.
  3. Decrease the barrel temperature until 190°C then use POM to clean out the PS.
(3) ABS change to PMMA
  1. Inject all ABS material in the barrel.
  2. Set the temperature of ABS material then use PS to clean out ABS.
  3. Decrease the barrel temperature until 240°C, used wet PMMA to clean out the PS then use the dry PMMA to clean out the wet PMMA again.
For POM as the raw plastic material
(1) POM change to PC
  1. Inject all POM material in the barrel.
  2. Set the temperature of POM material then use PE to clean out POM.
  3. Increase the barrel temperature until 290°C then use PC to clean out the PE.
(2) POM change to ABS
  1. Inject all POM material in the barrel.
  2. Set the temperature of POM material then use PS to clean out the POM.
  3. Increase the barrel temperature until 220°C then inject out until clean.
(3) POM change to PMMA
  1. Inject all POM material in the barrel.
  2. Set the temperature of POM material then use PS to clean out the POM.
  3. Decrease the barrel temperature until 240°C, used wet PMMA to clean out the PS then use the dry PMMA to clean out the wet PMMA.
For PMMA as the raw plastic material
(1) PMMA change to PC
  1. Inject all PMMA material in the barrel.
  2. Set the temperature of PMMA material then use PE to clean out PMMA.
  3. Increase the barrel temperature until 290°C then use PC to clean out the PE.
(2) PMMA change to ABS
  1. Inject all PMMA material in the barrel.
  2. Set the temperature of PMMA material then use ABS to clean out the PMMA.
  3. Increase the barrel temperature until 220°C then inject out until clean.
(3) PMMA change to PP
  1. Inject all PMMA material in the barrel.
  2. Set the temperature of PMMA material then use PP to clean out the PMMA.
  3. Increase the barrel temperature until the PP material melted and inject out until clean.
(4) PMMA change to POM
  1. Inject all PMMA material in the barrel.
  2. Set the temperature of PMMA material then use PS to clean out the PMMA.
  3. Adjust the barrel temperature until 190°C then use POM to clean out the PS.
(5) PMMA change to HIPS
  1. Inject all PMMA material in the barrel.
  2. Set the temperature of PMMA material then use HIPS to clean out the PMMA.
  3. Increase the barrel temperature until the HIPS material melted and inject out until clean.
For PP as the raw plastic material
(1) PP change to PC
  1. Inject all PP material in the barrel.
  2. Increase the barrel temperature until 290°C then use PC to clean out the PP.
(2) PP change to POM
  1. Inject all PP material in the barrel.
  2. Increase the barrel temperature until 190°C then use POM to clean out the PP.
(3) PP change to ABS
  1. Inject all PP material in the barrel.
  2. Increase the barrel temperature until 240°C then use ABS to clean the PP.
(4) PP change to PMMA
  1. Inject all PP material in the barrel.
  2. Increase the barrel temperature until 240°C used wet PMMA to clean out the PP then use dry PMMA to clean out the wet PMMA.
(5) PP change to HIPS
  1. Inject all PP material in the barrel.
  2. Increase the barrel temperature until 240°C then use HIPS to clean out the PP until clean.
For HIPS as the raw plastic material
(1) HIPS change to PC
  1. Inject all HIPS material in the barrel.
  2. Increase the barrel temperature until 240°C then use PE to clean out the HIPS.
  3. Increase the barrel temperature until 290°C then use PC to clean the PE.
(2) HIPS change to ABS
  1. Inject all HIPS material in the barrel.
  2. Set the temperature of HIPS material then use ABS to clean out the HIPS.
(3) HIPS change to POM
  1. Inject all HIPS material in the barrel.
  2. Set the temperature of HIPS material then used POM to clean out the HIPS.
  3. Increase the barrel temperature until 290°C then use POM to clean the HIPS.
(4) HIPS change to PMMA
  1. Inject all HIPS material in the barrel.
  2. Increase the barrel temperature until 240°C used wet PMMA to clean out the HIPS.
(5) HIPS change to PP
  1. Inject all HIPS material in the barrel.
  2. Set the temperature of HIPS material then used PP to clean out the HIPS.

When operation injection molding machine, the plastic material and color must always be change. If the basic theory on how to change the material or color isn’t enough, it would be wasteful to the plastic material and time. There is a brand of cleaner to clean the barrel in the market. This brand is called CORATEX made in West Germany. It’s very helpful for Screw, injection, Nozzle Head, Screw Head And Mold (specially for hot runner mold). It is also very helpful for changing the material’s color and save time.