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November 2, 1999

2 Min Read
Healthy barrels produce healthy parts

Three years ago (October 1996 IMM, p. 93) we told you about the Ultramax barrel from Inductametals and its ability to hold up to heavily filled resins. We also told you about two molders, each of whom was going on three years with the same barrel, processing material with glass loads ranging from 33 to 55 percent.

Now, with a few more years under the Ultramax belt, another advantage of molding with this durable barrel has come to light. Bruce Newman, process engineer at Kingston Timer, based in Smithville, TN, reports that part quality has improved and scrap rates have declined, thanks to resin cushion repeatability achieved with the barrel. The Ultramax, as a refresher, is produced using a proprietary induction process, rather than a furnace-cast process. The result is increased corrosion and wear resistance.

Kingston, a manufacturer of appliance timing products, runs 35 presses (Van Dorn, Newbury) ranging from 50 to 170 tons. Some 80 percent of the material the molder runs through the presses is mineral filled, and the company has an Ultramax barrel on each machine to combat wear.

Newman says that since the barrels were installed about three years ago, he’s tracked statistical improvement in part quality and scrap rates. He attributes it to reduced wear not only along the barrel wall, but around the check ring and screw as well. This helps the screw build a more consistent shot each cycle.

“If there is less variation in the melt quality, there is a lot less variation in the finished part,” he says. “The fact that they wear less also allows you to maintain cushion standards, if you’re monitoring those. They have improved dramatically for us.”

On seven of its presses Kingston has installed special process controllers that graph cushion repeatability. Once a month that graph is drawn for 40 consecutive shots and recorded. Newman says this curve has remained steady for several years. One machine, for example, with a cushion setpoint of .30 inch (±.05 inch), has an actual cushion of .31 inch. Another graph produced by Kingston tracks scrap rates, which Newman says have been in steady decline over the last three years.

He reports that molding life at Kingston prior to Ultramax was filled with unpredictable quality and deteriorating cushions. “Before, with the wear factor being much higher, we’d start to see cushion variation within two months of installation of a new check ring when running our abrasive materials,” reports Newman. “Now we don’t, and haven’t yet. And we’re coming up on three years.”

A consistent cushion has also given Newman greater confidence in his molding machines’ ability to cut off at the same position each cycle. As a result, Kingston is on the verge of investing heavily in cavity pressure sensing technology. “I would not have even considered transducers without these barrels,” he says.

Contact information
Chicago, IL
Ted Krengel
Phone: (312) 467-1031
Fax: (312) 467-1049

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