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Two-Step Purging: High-to-Low Temp Changeovers Without Black Specks

Two-Step Purging: High-to-Low Temp Changeovers Without Black Specks

Going from high to low temp resins without carbon is a difficult task. Asaclean's Purging Compounds are ideal for difficult changeovers.

We know that very few plants are only running super-engineering resins, engineering resins, or commodity resins. It’s great to know how to deal with these resins individually, but many Asaclean® customers come to us for help changing between low and high temperatures. You may run lots of different materials, and different materials usually require different processing temperatures.

We understand that due to customer demands, production needs, or scheduling, a mold may need to move from machine to machine. This also causes excessive material changes. You can do everything right, but sometimes these increased changeovers may be out of your control. Often, we see these changes going from high to low melt temperatures. These are usually the most difficult changes to accomplish (especially when rushing to hit a customer deadline). What do you do when you’re on the clock and need to run good parts right away?

We have some good news and some bad news.
The bad news is that there isn’t an individual product that will solve the issue.
The use of a single purge does not allow you to change the temperature from normal process ranges to that of a super-engineering resin like ULTEM to something low temp like TPU.

Attempting this change would cause serious degradation of the low temperature resins or freezing up of the ULTEM. In the long run, both cases cause black spots on the pieces and would likely necessitate a total teardown and screw pull.

The good news is that our Asaclean® Purging Experts have the products and the expertise to help you complete these changeovers quickly and easily. The winning solution is a two-step purge using a combination of two specialty grades of Asaclean® optimized for this production scenario.

Say you need to go from running PEEK to ABS.  You need to fully remove the PEEK from your screw and barrel, or you will have serious contamination issues.

First, purge the PEEK with PX2 or PF Grade and gradually lower the temperature to the lower end of PX2’s operating range. This will give you the confidence to know your barrel has been fully cleaned and that you are not experiencing layering.

Next, chase the PX2/PF Grade with a general-purpose purging compound like U Grade or a scrubber like EX Grade and gradually lower temps and purge thoroughly before switching to the ABS.

This allows you to make the transition from a temperature range above 700°F for super-engineering resins and painlessly step down to a lower range for engineering resins. Reverse the order and grades of purge if you need to step back up to the higher range.  Please note that this is not the kind of project to try without the assistance of an Asaclean Purging Expert.  Schedule a free consultation today to make sure your application and processing environment make sense for these recommendations. 

Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.

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