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| Author | Topic: Grooved feed zome extruders |
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sami Member Posts: 2 |
posted August 10, 2003 04:06 AM
   
Grooved feed zone will hekp for the better feeding. why in all extruders people dont use the grooved feed zones?? Is there any disadvantages of grooved feed zone single screw extruders. Can any one explain IP: Logged |
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zabielski Senior Member Posts: 214 |
posted August 10, 2003 07:52 AM
Essentially COST. It is more expensive. The bean conters ought to have their brains "groved" first hand. IP: Logged |
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Peter P Senior Member Posts: 58 |
posted August 10, 2003 09:14 AM
Grooved feed sections generate much higher pressures in the barrel, which, in turn, lead to the break-down of the lubricating layer of polymer melt between the screw flight and the barrel. The absence of this lubricating layer means that you get metal to metal contact and severe screw wear. Instead of a screw lasting 3-4 years, for some materials, like HDPE, and some screw designs you can lose 40 thou off the screw flight in about 6 months. If you take account of shorter screw life in your costings and find that the higher cost can be accommodated by your increased throughput then Grooved Feeds are economical - otherwise, stay away from them. ------------------ IP: Logged |
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Tom C Moderator Posts: 178 |
posted August 10, 2003 09:36 AM
The interaction between meterials and grooves is as complex as any other interaction in extrusion. In which case the design of the extrusion process must consider the presence of the grooves. So in some cases the extruder will run great with the grooves, and in other cases the grooves may cause more problems than they are worth as explained previously. Additional problems with grooves not yet mentioned are pre-mature melting which fouls the grooves and destroys the effect, and cleanout problems when this occurs. There are many variations of grooves. Some designs are mild in effect and I have used these to great advantage over the years. Some designs are so effective in pressure generation they can rupture a barrel. So careful choices must be made when using grooves. Tom C IP: Logged |
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Steve H Moderator Posts: 230 |
posted August 11, 2003 01:30 AM
Some other disadvantages and benifits. Reprocessing regrind can be a bit problematic with a grooved feed section. Very good cooling in the groved feed section is vital too. At least 10% more HP to drive a screw of a given size with a grooved feed. A quite shallow intial feed section, which gives way to a deeper feed section at the end of the groves will cut down the extreme pressure generation. Higher throughput, more consistant plasticising and lower melt temps (allowing the downstream to keep pace with the greater output. The old story, you don't get something for nothing Steve H IP: Logged |
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T.K.Palanisami Senior Member Posts: 25 |
posted August 11, 2003 07:37 AM
Please have look in the following link. http://www.polymerlinks.com/discussion_reply_list.php?qid=64&id=2&name=Extrusion&topic=Grooved%20feed%20zine%20in%20the%20single%20screw%20extruders I hope this helps Regards IP: Logged |
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Bob Cunningham Senior Member Posts: 56 |
posted August 11, 2003 09:08 AM
Soft pellets (like EVA for example) can actually get cut up by the corner of the groove, which will give poor feeding. On a stiff pellet like HDPE, the pellet is stronger and won't get cut up so it will convey very well. If the grooves get clogged with fluff (like mentioned above), essentially you have a smooth-bore extruder, with a screw designed for grooved-feed and your feed rates will go in the toilet. -Bob Cunningham IP: Logged |
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TomBlack Moderator Posts: 35 |
posted August 18, 2003 09:08 PM
Sami, You can find some comments on grooved feed extrusion on our website www.ppsincorp.com
------------------ www.ppsincorp.com IP: Logged |
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