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| Author | Topic: Choosing an extruder and/or screw |
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Harold Member Posts: 2 |
posted July 19, 2005 03:21 PM
   
We currently use a single screw extruder, two stage screw and for the most part it seems to run fairly well except their is some venting issues. All I can say it is a metal loaded polymer with a 4-6.oo specific gravity that we premix before running through the extruder. I would like to know is why some one would choose a single screw over a twin screw, one stage vs two stage screws and their pros and cons. I am new to this forum and any information would help and maybe help out others. ------------------ IP: Logged |
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Tom C Moderator Posts: 555 |
posted July 19, 2005 03:55 PM
Venting allows you to add materials (like your metal) and have the gases dragged along for the ride go out the side of the extruder, rather than in the product. For pelletized materials that are dry enough, you can get away without a vent if the screw is properly designed. If you mix other materials into the pellets, a vent is almost required. These principles apply to all extruder types. Single screws are general purpose and inexpensive to purchase. They can be made to do a lot of different things, but a lot of skill and tricks of the trade are required to perform complex jobs. Fully intermeshing co-rotating twin screw extruders have a lot of flexibility when it comes to mixing, and are therefore favored for compounding. Counter rotating fully intermeshing twin screws are generally used to make rigid PVC profiles because of their positive pumping characterisitcs. Those are the big three. There are lots of of other configurations of screws for a variety to tasks. ------------------
Tom Cunningham
Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
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