I regularly hear from processors who are generating large amounts of resin dust—sometimes hundreds of pounds each week. They collect it, shift after shift, from the dust collection bins near their conveying system’s vacuum pumps.
Those producing black-colored parts might be able to utilize some of this wasted resin dust by mixing it with virgin resin and molding it into parts. But for those making transparent or light-colored parts, using up the dust isn’t practical. Whenever you mix dust with pellets, the small resin particles are going to melt far faster than the pellets. Then, they overheat and burn black by the time the rest of the resin is ready for injection, leaving you with a marred part.
So, is there any way to get rid of all that dust and wasted material? How do you solve the problem?
Excessive dust is a conveying and resin related problem, associated with excessively high air and material speed used in typical “dilute-phase” conveying systems. As pellets go rocketing along (5,000 ft/min or faster), banging into the walls of the tubing and elbows, they degrade, creating the dust that ends up in your filter bin. Though many people associate dust generation with harder engineering resins, no resin is immune when moving at high velocity. Certain pellet shapes seem to exacerbate the problem as well.
There are lots of retrofit conveying components that claim to help with pellet shattering and dust problems, but none of them address the root problem—excessive air and material speeds in the conveying system. The obvious fix is to dial down the air speed. However, if you’re a processor who needs every bit of throughput you can get to keep your machinery producing, slowing down conveying speeds isn’t possible with the conveying equipment you currently have. Your vacuum pump will only hold so much material in suspension and you’ve got to move it as fast as possible to maximize throughput. The dust and the processing problems come with that.
But there is a great fix out there. To address the dust problems of high-speed, dilute-phase conveying, Conair developed Wave Conveying™, a patented system that retrofits to existing conveying lines to provide substantially higher resin throughputs at lower conveying speeds. Wave components controls air velocity and material velocity independently. Wave also controls the conveying stream density for maximum throughputs with a minimal dust and no angel hair formation.
Wave Conveying combines a long-distance, deep vacuum pump, a variable frequency drive, an FLX-128 Plus Conveying Control, and other components to enable processors to convey dense slugs of material at slower speeds (300-1800 fpm). Conveying speeds can be customized to each material destination while greatly reducing dust generated.
If you’ve never seen this system in action, or compared it to typical conveying, here’s a quick video:
One other thing: The Wave Conveying system still supports traditional dilute-phase conveying if you need it. But after you try it, I don’t think you’ll want to go back.
If you’ve got questions about a conveying problem, Conair has answers. Just give us a call.