Extrusion basics: Let’s talk garbage

Yes, I’m reminding you again that there are no toxic plastics, and we are the missionaries that must convey this true gospel to the masses. This is a gospel with scientific validity, so why doesn’t everyone believe it? Send your comments to me at [email protected] or talk to me in person at the NPE/ANTEC by calling my cell phone before, during and after, at 301/758-7788.

My extrusion topic this month is garbage. Not trash, a word we may use to avoid the dirtier word, garbage, but also a word with many other meanings. Garbage is stuff we don’t want and can’t use. We especially don’t want it in our products. People who can’t say the word “garbage” may have the handicap (at least in a factory) of delicacy.

Fish eye
Why a fish? Read on—all will be revealed.

Whodunit? As a tech service engineer for a major resin supplier, I had the delicate task of trying to show that we didn’t do it, that it didn’t come in with the resin, that we were clean but something—or someone—else was at fault. And we had to make our case to people who wanted to pin the tail on us, so they could get a refund or resupply or some other atonement for our errors.

Wadizzit? Our defensive tactics included questions, a microscope, some knowledge of the material and extrusion conditions and sometimes the inside of the melt pathway. Also time. Even if you are in a rush, never show it, as that exposes weakness, and you may accept some responsibility just because of your time stress. Follow the three Ps: Patience, politeness and persistence.

Questions include asking for samples of the contaminated product and, if possible, samples of the resin used to make it, along with ID (product, lot and container numbers); how and when it was delivered; and any tests done on the resin before it was used. (See my column from October 2015, which dealt with testing of incoming resin.)

Sometimes it was possible to show that our resin couldn’t have been the problem, because it was delivered after the problem was first seen, or the particle size and shape weren’t ours (strands versus pellets, for example).

Offer to run a sample in a lab extruder. I say offer, because you may never have to do it. If the “plaintiff” thinks it might not be us, but we are the deep pockets that want to keep the customer, he may accuse us even with no technical evidence, which is the next thing we should ask for.

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