Purging 101

By Tim Cutler

Related links: Purging | Dyna-Purge Grade Selection Guide | Cost-To-Purge Calculator

Let’s begin by reviewing the reasons for purging. By definition, purging is to 'undergo or cause evacuation.' For plastic processors, purging is an essential part of the cleaning process. Done properly, purging should:

• Effectively displace the resident resin
• Eliminate the resident resin in dead spots or negative flow areas
• Remove heat sensitive resins, additives and pigments, which are susceptible to degradation
• Eliminate black specks produced by carbon build-up

This question comes up often and there are three common reasons for purging:

1. Changeover: the changeover between jobs, since purging will remove previous colors, resins and carbon build-up that will contaminate future production
2. Shutdown and Startup: are sources of degradation caused by excessive heat exposure to the resin
3. Routine Preventive Maintenance: purging can help extend the operating life of plastic processing machinery.

Can any company afford not to take advantage of the benefits commercial purging compounds deliver, in today's competitive global market? Processors need every advantage they can get. For example:

How long does it take to complete a color/material changeover?
If your team spends hours every week performing color or material changeovers, purging could save you valuable time and money. In one case, a molder who performed 9-10 changeovers per week began using a purging compound and recovered over 1,000 hours of machine/operator time per year. This time is now used to produce parts that have resulted in increased profitability for the molder. View case study.

What is your scrap rate? No doubt, it is targeted for improvement.
Many times when a molder performs a material changeover, they’ll simply start running parts with the new material and wait until the previous resin is purged completely before making good parts. The problem is that this results in a very high scrap rate, lower efficiency, and waste of valuable production resin. Using a purging compound will reduce the time it takes to get the old resin out of the machine, which allows you to start making good parts faster. Coupled with the hard dollar savings you receive by saving production resin, this efficiency can save you thousands of dollars per year on a single part. View case study.

What does downtime really cost?
Time is our most precious resource because once you use it, you can’t get it back. Downtime is especially painful when your best machines are sitting unused because of material or color changeovers. A purging compound will at least cut your downtime in half, and many times companies will see huge production time and labor savings by simply using a purging compound. The following case study demonstrates how a molder recovered 240 labor hours and 104 hours of production time per year. View case study.

What savings can you expect from purging?
On the Dyna-Purge website, we provide a free cost-to-purge calculator to determine your savings.

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