SPECKS OF TROUBLE

摘要

There's no silver lining to black specks in tubing and pipe extrusion. Especially in clear or light-coloured parts, black specks cause rejects, wasted resin, unscheduled downtime, and ticked-off customers. Black specks are everywhere in the plastic extrusion industry, alas, but at least there's no mystery as to their source: either they were part of the incoming raw material, or the processor manufactured them in the extrusion system. If you have specks, how do you find out which of the two possibilities is to blame? Start at the beginning with the resin by examining statistically representative samples of the raw material. "A variety of commercial instruments are available today that allow analysis of millions of pellets," said Chris Rauwendaal, head of consulting firm Rauwendaal Extrusion Engineering Inc. "Pellets can be scanned and sorted not only for discoloured specks, but also for irregular pellets such as pellets with tails."