PVC Profile Extrusion Process
Profile extrusion is the process of making continuous shapes of plastic (not including sheet and film) by extrusion. Molten polymer is forced through a metal die cut into the linear shape of the desired finished article (channel, tube, etc.). The molten polymer exits the die and is drawn to the appropriate thickness in air. The article is then cooled and shaped by a forming/sizing collar in a water bath under vacuum.
Use chilled water to allow efficient cooling during sizing and quenching while minimizing profile agitation. Use a cooling tank length so that the finished profile does not shrink or distort prior to pullout and cutting. Use sufficient vacuum in the vacuum box to achieve proper profile dimensioning. It should be kept low enough to prevent dragging on the sizing sleeve to eliminate chatter marks.
Close control will need to be maintained on the cutting or sawing of the profile into the desired finished length to prevent splitting or shattering. A combination of part reheating and cutter-blade lubrication can significantly improve cut quality. Reheating the part can be accomplished by heated air or water. Use a reheat temperature of 50°C to maintain clean cuts and reduce part stress/bowing.