By Lynn Tryba
LANCASTER, PA—THE ACRYLIC WINDOW in a cell phone, the clear lens that covers a car's instrument panel and the plastic surgical instruments all need to be perfect, for any flaws will render them scrap.
Manufacturers often blame flaws in plastics on excess moisture, but the real contaminant may be the dust caused by the conveyance of raw material, says Jerry Paulson, president and chief executive of Pelletron Corp.
Raw material becomes contaminated whenever it is moved during the manufacturing, storage, shipping or processing stages. The resulting friction causes small pieces to break off and form a fine dust that clings to the raw material.
What this means in the plastics industry is that when a molder melts the dusty material to make a precision part, the dust will “go from a solid to a liquid to a gas or it will burn,” says Paulson. “And that gas will create a spot inside the particle. If it's a clear material, it creates a scrap.”
According to Paulson, Pelletron's Deduster works by breaking the attraction of the dust to the raw material. For example, plastic pellets are fed into the Deduster by gravity. They fall onto a wash deck, which is porous so that air can flow up through the pellets. As the air washes over them, an electromagnetic field breaks the attraction, allowing the dust to be pushed above the pellets. The dust is lifted to a dust outlet and the clean pellets drop from the machine.
The system works in a similar manner with food products such as coffee, grains and cocoa.
Thirty percent of Dedusters are being sold to plastic product manufacturers, many of which use the machines for regrind recovery. “The high level of dust in regrind makes it difficult to mix with virgin material and get a good finished product,” Paulson says. “When they remove the dust from the granulate, they can get a resin almost as good as the virgin material.”
In a test report, Nypro Inc. (Clinton, MA), a medical device manufacturer and global provider of precision injection molding, found that by mounting a Deduster on top of a drying hopper, it was able to stop the burning of fine dust and reduce the contamination on its clear medical parts. The report credits the technology with greatly decreasing scrap at Nypro's Oregon plant and increasing yields on clear materials.