Top tips for extrusion


Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.




Optimise tempering

Self-optimising, closed-loop screw tempering for counter rotating twin screws affords more cooling effectiveness than oil tempering – and is free of maintenance. Internal screw tempering helps to widen the process window and increase screw output. It gives constant temperature profile at all output levels and avoids excess temperature in the front section of the screw.


Eliminate free cuts

To process PVC, extruders need a specific temperature, shear and residence time. So, a counter-rotating twin screw needs 6-8 different zones. Most designs have free cuts (gaps) between zones, which change residence time and shear rate. These can be eliminated by a continuous change of the lead, and by starting and stopping flights inside the channel.


Minimise temperature rises

Counter-rotating twin screws typically create high temperatures in the metering zone, so barrel cooling here must be intensive. Often, cooling systems cannot absorb enough heat. Screw designs with an optimised roller gap and a flank gap system run a high pressure on one hand and have a small melt temperature increase on the other. High pressure is used to make thin-wall pipes, corrugated pipe and thin-wall profiles.


Reduce wear

Primary wear is caused by screw design, so can be reduced by optimisation. Secondary wear is caused by the rheology of the screw and barrel steel. It can be reduced by wear protection, by running a nitrided screw in a nitrided barrel. A higher level of wear protection is achieved by

PTA-welding on the running surface of the screws, and a bimetallic layer inside the twin screw barrel.


Cut maintenance

GTS achieves barrel tempering with ceramic heater bands and maintenance-free air cooling.

The bands direct heat into the barrel instead of into the surrounding air. Heater design is aligned with the screw design and optimised for energy saving. It also delivers optimised barrel tempering within a wide process window.


If you need more information, Ningbo Fangli Technology Co., Ltd. welcomes you to contact for a detailed inquiry, we will provide you with professional technical guidance or equipment procurement suggestions.


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