7 quick purging tips for extrusion blow molding

In a continuous process like extrusion blow molding, contamination has a detrimental effect on your business’s bottom line. Blow molding tends to have bigger issues than other processes. Once contamination begins, it’s almost impossible to stop it without aggressive intervention — usually through a screw pull or use of a purging compound. Effectively purging your thermoplastic processing equipment is critical if you want to stay competitive. Not only do material changes occur more frequently, but waste disposal is more difficult (and more costly) and a greater number of customers demand just-in-time, customized products. For many blow molding plants, reducing waste, time and cost are some of the most significant factors for staying competitive. Many customers have more than a 70% reduction in costs with the right purging compounds, saving them up to tens of thousands of dollars each year.

Until recently, the most popular method for purging extrusion blow molding equipment had been to use the next processing resin or regrind. However, this approach results in longer purge times, higher scrap rates and greater residue buildup over the long term.

Here are seven quick tips for using purging compounds in order to keep your purging operations as efficient as possible:

Tip #1: Don’t use production resin to purge your machine

Production resins are not designed to clean machines and are not a substitute for commercial purging compounds. Purging your blow molding machine with the next resin or regrind is time-consuming, wasteful, and ineffective at removing color and carbon contamination. When you use regrind or virgin resins to purge, the material creates another layer over any existing resins, color deposits or carbonized material within the barrel and on the screw. In time, these layers become additional sources of contamination, making purging even more difficult. Once your machine returns to production, carbonized materials eventually break free and contaminate your products.

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