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jdelmedico Member Posts: 2 |
posted September 25, 2003 11:32 AM
   
I am looking for the recommended screw types for about eight different plastics. Currently we use one screw type for all different plastics. The plastics are PU, PVC, TPR, PP, PE, EVA, and surlyn. We use a couple of different extruders. The one that I am inquiering about has a barrel that is 1" 24:1 ratio. [This message has been edited by jdelmedico (edited September 25, 2003).] [This message has been edited by jdelmedico (edited September 25, 2003).] IP: Logged |
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Tom C Moderator Posts: 218 |
posted September 25, 2003 03:56 PM
We need more info: What is the basic process; profile? Do you mix anything with the plastic? Do you pre-dry? Is there a vent? Add any other information you can think of that might help. Tom C IP: Logged |
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jdelmedico Member Posts: 2 |
posted September 25, 2003 05:13 PM
The process is wire and cable. Most of the products are only mixed with colorant. Some of the plastic types are pre dried others are not dried at all. There is no vent. The plastic as well as colorant is pellet form. Some more information about the machine for a particular PU: Melt temp at die 380 F PSI at exit 1000 Screw RPM 81 Motor Amps 6.5 If any other information would be of assistance let me know. Joe D IP: Logged |
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Tom C Moderator Posts: 218 |
posted September 26, 2003 08:33 AM
The best choice of a screw is one designed specifically for each resin grade. Usually this is not economically feasable. The next best choice would be a screw designed for each resin type, and perhaps a low and high viscosity screw for each type. Again, expensive. The third choice would be a set of screws that would handle; 1) Low to medium viscosity amorphous polymers. It is more unusual to find high viscosity crystalline polymers, so often a screw is not needed for this case. What companies often have is one screw to handle all things. The best design I have seen for this, with the qualification that it is a great compromise in some cases, is a shallow Mallifer style barrier screw with a Saxton mixer. Tom Cunningham IP: Logged |
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charliehagee Senior Member Posts: 5 |
posted October 01, 2003 09:50 AM
Wayne Machine is an excellent source for 1" size custom screws to process specific polymers. They build the extruders as well as custom screws. See www.waynemachine.com or call them at 973-256-7374 IP: Logged |
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griffex Senior Member Posts: 18 |
posted October 11, 2003 11:46 AM
Dear Joe What counts is the actual design, and that means real numbers, especially channel depths. There are so many varieties of each material that it is misleading to link screws to their materials. Tom's idea of three screws is a good one, as it links screws to a material's property (viscosity, crystallinity) not just their names. Consider a static mixer or even a mixing set of breaker plates, as well as different screen packs, as all interacting with the screw design, and making it less important to have one screw for each material. Allan Griff algriff@griffex.com IP: Logged |
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