Pet Preform Plastic Injection Molding Process: Color Change with EasyPurge Purging Compound

OPAQUE White to Clear

Goal: Color change time reduction


Machine: Netstal 3500-3700 

Extruder Diameter: 135 mm

Material: PET

Colour: Opaque White to Natural

Mould: 54 x 64 grs

Factory Location: USA

1. Original Prefrom Color: Opaque White.

2. First, once the barrel and the piston were cleaned with Easypurge purging compound, virgin PET started to be injected into the mold.

Easy purge was dosed into mixer using Easypurge’s Automatic Purging System (APS).

3. Easypurge emulsifies colour pigments injecting preforms in automatic.

4. The Easypurge Automatic Purging System stopped adding purging compound. The process was finished using virgin PET to remove the rest of impurities and colour pigments emulsified by Easypurge.
5. Finally, the dosing of Easypurge was stopped, using virgin material to remove the rest of the purging compound leaving the hot runners clear of colour contamination.

The machines parameters were adjusted due to an increase of the MFI. 

24 hours later we confirmed there was no presence of White PET contamination during the next two shifts. 

Color Change During Plastic Injection Molding Process: Final Results


Purging Compound used


Colour Time Changes

Pellet Purging compound

48 Kgs

700 Kgs



1050 Kgs

300 Kgs


Comment by the Process manager:

“Cleaning Hot Runners in automatic with Easypurge doser is helping us a lot, since we work with 18 different colours .”

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Let’s improve quality and simplify your purging process while reducing change-over time, together.

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