Color changes are one of the biggest headaches processors face. Color changes are difficult no matter your process. Fortunately, there are a few tips that I find make your life much easier when you're struggling with a tough change.
When purging during color changes remember these 3 tips.
- High Back Pressure
- Medium to High Screw Speed
- Increase Nozzle Temperature 50°F
- High Back Pressure
The most important thing to remember when doing a color change is to use enough back pressure to keep the screw all the way forward. This insures that the purging compound will be able to work the entire length of the screw and clean the trailing edge of the screw flight. The trailing edge is a common hang-up area for degraded material. Without sufficient backpressure this area will not be thoroughly cleaned.
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Medium to High Screw Speed
The second thing to remember is that mechanical purging compounds rely on shear and friction to clean your machine. Use as much screw speed as is safe and practical. The high screw speeds coupled with high back pressures will generate maximum shear and friction to yield the best results during purging. - Increase Nozzle Temperature 50°F
Lastly, the most common hang-up area for contamination and degradation is in the nozzle body and nozzle tip. A tried and true tip for addressing this area is to bump the temperature up on the nozzle by 50°F when you first start the color change. The extra heat during the purge process will allow degradation in nozzle to break loose and be displaced by the purging compound. This will result in a more effective purge.
If you follow these tips you will be more effective, more efficient, and more profitable.
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