Posts: 386
From:McHenry, IL USA
Registered: Nov 2002

posted December 28, 2002 11:05 AM               

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I've been asked to send one ton of several materials to a Consultant so that he can "perfect" an idealized screw design for each.

This sounds way out of boands from a volume basis. Is this unusual, or common?

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Posts: 59
From:
Registered: Jul 2001

posted December 28, 2002 02:27 PM               

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It depends on the size of the extruder, and how long the trial process takes.

For instance, at 4 1/2" extruder will go though a ton in a little under an hour at max speed.

I don't think a ton is out of the ordinary, but again, depends on the extruder size.

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Posts: 386
From:McHenry, IL USA
Registered: Nov 2002

posted December 29, 2002 08:37 AM               

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Thanks felix: What I'm confused about - and need more information on - is the number of screws they want to try my materials on.

I thought rheology would be used to model each screw - thereby neccesitating considerably less materials.

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Posts: 59
From:
Registered: Jul 2001

posted January 01, 2003 05:30 PM               

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It is true that mathematical models have come a long way and they reduce the trial and error phase of screw design, however there isn't a screw simulator out there that is 100% accurate all the time, for different screw geometries, polymers and process conditions. It's a good starting point to simulate screw performance, but the proof is in the pudding, necessitating trials of your resins on a screw design for verification.

If I were designing the screw for your resins I would probably first test it on my general purpose barrier screw design and then see the outcome of that trial before going back to the simulator to come up with a more optimized design.

As for how many screws they will want to test your materials on, that’s anyone's guess since I don't know what procedure they would use to arrive at a more optimized screw design for your resin.

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Posts: 386
From:McHenry, IL USA
Registered: Nov 2002

posted January 02, 2003 07:10 AM               

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Felix:
This year, I will find out and keep everyone posted. It will be interesting indeed.

I wish you the best for 2003.

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Posts: 115
From:Amesbury, Mass
Registered: Nov 2002

posted January 04, 2003 06:16 PM               

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If it makes you feel any better, when conducting a trial on a 7-layer blown film line, it is common to require about 5-8 tons of materials just to get one square meter of useful film. That might be slightly different, but in that case you had to completely fill each extruder (pushing out the material from the previous run) and die layer, then take a while to optimize the conditions (temperatures, etc.), let the blenders settle out, then you can make your film. Then after you have your square meter, we need to clean out the whole line again, which requires various material to purge out each layer.

People would frequently second guess the material requirements, then be very disappointed when we ran out of material before the trial was complete - a big waste of tons of resin, and usually several airfares to come observe.

-Bob Cunningham

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Posts: 386
From:McHenry, IL USA
Registered: Nov 2002

posted January 05, 2003 07:04 AM               

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Thanks Bob.

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