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| Author | Topic: Extruder Feeder for LD |
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Gray Dick Member Posts: 1 |
posted May 29, 2006 12:06 PM
   
Hello I have just started to recycle LDPE and I have designed a force feeder in a hopper to push the product into my extruder. The feeder does not feed consistantly and the extruder screw does not fill with product. I have been to a few companies that manufacture screws but they cant help me with a screw design that works, please can you help me? ------------------ IP: Logged |
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Tom C Moderator Posts: 710 |
posted May 29, 2006 12:18 PM
Welcome to the forum. I can help, but some clarification is needed. What is the form of your reclaim (flake, crumb?) and what does the feeder look like? Is it a "Crammer" style, which is a verticle screw pushing down onto the extruder screw? ------------------ Tom Cunningham [This message has been edited by Tom C (edited May 29, 2006).] IP: Logged |
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Stephen J. Derezinski Senior Member Posts: 36 |
posted May 29, 2006 02:18 PM
Mr. Gray-- I had some experience with flake and powder mixture of another polymer. When the flake concentration got high, over 10%, then the mixture behaved like "wet leaves." Bridging in the feed hopper was a problem. We had to limit the amount of flake to make it work at all. I did not try a vibrator, but that may have been some help. You should check the bulk density vs pressure of your mixture to get started. If it is radically different from the virgin resin, then your standard screw will likely have solids conveying problems. This can be easily done and could be very instructive. The effect of the flakes on the friction factors is much more difficult to determine. Some initial experimentation with solids conveying zone temperatures might give some indication of this problem. Try changing back pressure on the extruder, if you can, to see how much the flow rate changes. (This is a little tricky, however, especailly if you have a "sick machine.") If flow rate and change in flow rate for virgin resin and mixture are the same, then you can assume that the friction factors have not been greatly altered. However, it sounds like you cannot get steady flow at all, so this test would not be possible. Stephen J. Derezinski, Ph.D. ------------------ IP: Logged |
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Steve H Moderator Posts: 381 |
posted May 30, 2006 02:54 AM
G'day Gray Welcome to the single screw forum. What percentage of your feed is reclaim? What shape is the feed throat on your extruder, Round (directly centred on the screw)? If this is the case, a rectangular one slightly off set may promote better feeding. Experimentation with barrel temps may help promote more consistant feed, what temps have you tried? Best regards ------------------ If at first you don't succeed, skydiving is not for you. IP: Logged |
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john green Senior Member Posts: 18 |
posted June 05, 2006 09:27 AM
I think you will always have problems feeding recycled flake into a screw unless you look at how Erema and such like companies heat this material prior to feeding then screw feed this directly into the feeding screw a much better solution is to Pelletize Sorry to be so negative butI hate flake pellets are much better to feed and convey IP: Logged |
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