posted July 15, 2004 07:12 AM               

Use a narrowing (neck-in) die to increase your backpressure, then allow that transition to go into your I or U shape die head.

However, to optimize your shape, you want to immediately pass it into a spray-water vacuum box (long water though), then PULL - not allow your extruder to PUSH.

This is referred to as pultrusion. You will need a very strong - repete - a very strong puller.

Nothing beats success - like SUCCESS.

posted July 16, 2004 02:59 AM               

Thank you very much for your valuable suggestions. What kind of L/D ratio would be required in the Extruder?

Should we look for any specific design of screw?

Should we look at pelletizing with Twin Srew Extruder & Than Extruding the Profiles of Single Screw Extruder or Irthere a method to extrude these Profiles Directly.

quote:

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Originally posted by zabielski:
You ought to consider extruding this without a breaker-plate or screens, as they will clog up quickly.

Use a narrowing (neck-in) die to increase your backpressure, then allow that transition to go into your I or U shape die head.

However, to optimize your shape, you want to immediately pass it into a spray-water vacuum box (long water though), then PULL - not allow your extruder to PUSH.

This is referred to as pultrusion. You will need a very strong - repete - a very strong puller.

Nothing beats success - like SUCCESS.

Keep us posted, eh?

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posted July 16, 2004 06:37 AM               

I would think though that a 32:1 L/D single screw extruder should work very well, and NO, don't subject the material(s) to another heat history by pelletizing (which also adds costs).

The trick is to have a grooved feed section with a compression ratio of about 3.5 to 5 to 1.

You essentially would grind up the material, assure that it's kept dry, then auger it into a very large surge bin. The bin would be slightly pressurized, and be off-set to the feed hopper. The delivery would be into a large hopper VIA an auger feed from the surge bin. Your hopper could be made from polycarbonate sheet, and have an air inlet, so you can blow a slight (very slight) amount of air towards the fill rate sensor.

This keeps the sensor clean and prevents surges.

Now, hook up you auger feed rates and latch them to a PLC so that your screw speed would sycronize with the feed augers, as you ramp speeds up & down.