SCREWS AND BARRELS | MACHINERY
Banishing rejects A Xaloy barrier/mixing screw, designed by Nordson, helped a pipe extruder solve a long-standing series of production problems. A production line at US-based pipe manufac-
turer Polyethylene Technology was exhibiting wide fluctuations in throughput caused by surging and – for heavy-wall HDPE pipe – consistently exhibited variation from the target wall thickness of 0.097in (2.46 mm). “We tried all sorts of solutions,” said Brad
Williams, senior manufacturing manager. “We looked for problems with the motor drive and the puller, tested four or five different 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.” Another problem was poor mixing of carbon
black, where an addition level of 2% was required. “We couldn’t get a good mix, and there were
always areas of the pipe with too little carbon black,” he said. The problems were solved by using the Xaloy
Efficient barrier screw with a Nano mixer in the metering section. Brad Casale, Nordson regional sales manager, said: “By preventing premature break-up of solids and increasing melting rates, the screw enhanced mixing and increased throughput on the line. The Nano mixer provided intensive mixing of the carbon black.”
As well as solving the surging problem, and delivering a homogeneous melt, the new screw increased the output of the extrusion line by around 12%.
Screw health Last year, Milacron extended the scope of its M-Powered ‘predictive analytics’ capability with an application to improve screw efficiency. Predictive analytics tracks machine condition
Nordson’s Xaloy Efficient barrier screw with nano mixer helped a pipe extruder solve production problems
and advises operators to take action in response to ‘early warning’ signs. This helps to ensure that maintenance is carried out before machinery failure – which helps to reduce downtime. “Through the adoption of machine learning and advanced analytics and AI, M-Powered can monitor signals of impending failure,” said Edward Jump, M-Powered IIoT digital analytics leader at Milacron. The company has now introduced an M-Pow-
ered application to improve screw efficiency. This allows users to order – and fit – a new, more efficient screw before production suffers. As a screw begins to wear – and its flights
deteriorate – it loses its ability to convey material efficiently. This leads to increased recovery time, energy consumption and increased melt tempera- tures. This can reduce productivity – as these conditions can increased cycle times – as well as potentially impacting part quality. Wear typically occurs slowly and is difficult to detect. Milacron says that its new system takes an energy- based assessment to assess screw performance. “Its touch-free functions can yield insight on the
screw’s health without adding sensors to the screw or barrel,” said the company. “This allows M-Pow- ered users to proactively order a new screw and
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