Extrusion - profile calibration and cooling
Extrusion calibration and cooling take place at the same time. For simple profiles, calibration may be a single metal plate calibrator followed by a chilled water bath, but for complex window profiles the calibration is usually with multiple metal calibrators (full or plate) in a full chilled water or spray bath.
* Check that the chilled water flow is stopped when the machine stops and that chilled water is not circulating on idle machines.
Check that there is good contact between the profile and the calibrators - this helps calibration and improves heat transfer.
Check that there is turbulent water flow around the profile and that no bubbles form on the extrudate. Check that chilled water is treated, chilled and distributed efficiently.
Find the maximum acceptable extrudate temperature after cooling and set the chilled water temperature to achieve this. Do not overcool the product. Insulate calibration baths to prevent parasitic heat gain to the chilled water.
Use variable-speed drives to control pumps to produce a constant pressure or flow rate. Use thermostatic controls to vary the flow rate based on the cooling demand rather than the pump's fixed output.
Dr. Robin Kent
Dr. Robin Kent--[c]Tangram Technology Ltd.
Note: Dr. Robin Kent is the author of Energy Management in Plastics Processing, published by Plastics Information Direct, and managing director of Tangram Technology Ltd., consulting engineers specializing in energy management in plastics processing, firstname.lastname@example.org.
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|Article Type:||Brief article|
|Date:||Jul 1, 2017|
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