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| Author | Topic: Extruding ability |
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jasonbae Member Posts: 1 |
posted October 08, 2005 10:47 PM
   
Same Extruder Diameter, Same Screw design but, different output,,,Why? I have single screw with Maddock, Extruder Dia. is 65mm, Another Question~ I am sorry for my poor English... IP: Logged |
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Tom C Moderator Posts: 616 |
posted October 09, 2005 01:07 PM
Lots of potential reasons why, but the most likely is due to differences in frictional feeding characteristics in the feed zone. The initial feed pressure, or lack of, can have a profound effect on the output of the screw. This is why groove feeding can show huge increaes in output. The flow rate of water into the throat, the finish on the screw and the height of material in the hopper can influence the output rate. This is how sensitive this area of the process can be. I try and design screws so that they will easily produce a high solids pressure without grooves. This will make like extruders run more consistant rates. As far as output, click on the extrusion rate calculator on; 1.8 Kg/rev seems out of the normal range for your size extruder. Sometimes that rate can be acheived on groove feed extruders, and APET might be a candidate for that. CPET would probably not work.
Tom Cunningham
Extrusion Technical Services [This message has been edited by Tom C (edited October 09, 2005).] IP: Logged |
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Steve H Moderator Posts: 373 |
posted October 09, 2005 03:44 PM
Greetings JB Welcome to the single screw extrusion forum, your English is much better than my Korean The barrel wall temp in the feed zone has a profound effect on a single screw plastic extruders output. If you experiment with a range of different temperatures, and measure the output achieved with each temp setting, you'll find that you will produce a bell shaped curve if you plot the output (Y axis) against barrel temp(X axis). The temp setting at the top of the bell is the optimum one for output. The other barrel zones can be treated in the same way, to develop a barrel temp profile that will give maximum output, but higher/lower temps in the other zones have less of an effect on output, than that of the feed zone. Cooling on the barrel section containing the feed throat, and cooling the screw also influence output. The shape of the feed throat also influences how much material can be drawn in.
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