Pinstriping can be an issue for extrusion applications dealing with pipe, some tubing, or blow molding with parison drops. It’s the last stand of the old material or color in a system that can take the most amount of time to properly clean. Many of the applications have mandrels in place that work to hold the inner diameter of the cylinder and keep the extrudant hollow in the middle. This dimension tolerance is extremely important but can be one of the toughest areas to clean.
Previous resin and color can stick behind the mandrels and if your procedure isn’t to tear down and clean manually that pinstriping could last for hours with a standard resin flush. Luckily, there are purging compounds on the market that greatly help with the issue of pinstriping. The best way to clean these systems is with a chemical purging compound and heat is key. You want to set a higher temp around the die where the mandrels are so that you get the most effective chemical activity in that region. This may be a secondary purge after cleaning the screw and barrel or it can be done in one shot, depending on the system and application.
Those are tough areas to clean but with the correct grade of purging compound in hand it can make a color or material change on these lines much easier for the user.
Ready to reduce your production downtime to protect your profits? Learn more about how purging compounds and process efficiency work in tandem.
Jeremy Cooley is an Asaclean Technical Service Representative & Purging Expert living in South Carolina. He's worked in injection molding & purging for over 15 years, and frequently presents at national plastics trade shows and conferences.