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Innovative Barrier/Mixing Screw Solves Persistent Plastic Extrusion Problem

Xaloy Nano-mixer
An extruder of polyethylene pipe was plagued with surging that caused wall-thickness variations and the inconsistent dispersion of carbon black. The manufacturer tried several fixes, none of which worked, until he installed an Xaloy screw with Nano mixer designed by Nordson.

Nordson Corp. has shared a recent success story, describing how its new Xaloy screw resolved a persistent problem plaguing a pipe extrusion line operated by Polyethylene Technology Inc.

The extrusion line exhibited wide fluctuations in throughput caused by surging and, in the case of heavy-wall high-density polyethylene pipe, variations up to 50% from the target wall thickness. “We tried all sorts of solutions,” said Brad Williams, Senior Manufacturing Manager, at the Lakeville, MN, plant. “We looked for problems with the motor drive and the puller, tested four or five alternate resins, and finally got a new screw and relined barrel — all with no success. Our gravimetric extrusion control showed fluctuations occurring every five or 10 seconds.”

The Xaloy Nano mixer from Nordson provides intensive dispersionary mixing of the carbon black. Image courtesy Nordson Corp.

Moreover, the polyethylene pipe extruder was having carbon-black mixing issues. The required addition level was 2%, but “we couldn’t get a good mix — there were always areas of the pipe with too little carbon black,” said Williams.

Polyethylene Technology turned to Nordson within months of receiving the screw from another supplier. “We recommended our Xaloy Efficient barrier screw with a Nano mixer in the metering section,” said Brad Casale, a regional sales manager for Nordson. “By preventing premature break-up of solids and increasing melting rates, the Efficient screw has enhanced mixing and increased throughput in the Polyethylene Technology extrusion line. The Nano mixer has provided intensive dispersionary mixing of the carbon black,” added Casale.

Besides solving the surging problem and delivering a homogeneous melt, the new Xaloy screw increased output. “As a result of using the new Xaloy screw, our target output rate has increased by 12%,” said Williams.

Forty-year-old Polyethylene Technology Inc. manufactures polyethylene pipe for municipal water, geothermal, pump and well, and irrigation applications.

Nordson develops and manufactures a range of systems for precision dispensing applications. Nordson Polymer Processing Systems provides customers with engineered components to melt, homogenize, filter, meter, and give shape to plastic and fluid coating materials.

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