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Author Topic:   rollround on die face

Posts: 1
Registered: Feb 2004

posted February 07, 2004 01:48 PM     Click Here to See the Profile for tellmemore     Edit/Delete Message   Reply w/Quote
Hi Guys,
I have just got involved extruding metallic particle loaded silastic silicone at extremely low output rates (approx 1kg/hr) through die opening of csa 4mm2. One problem we are encountering is material depositing on the die face around the die opening as we extrude & eventually falling back onto the extrudate to the detriment of the product. Can someone tell me exactly why this happens & pointers on how to overcome/correct it if they would be so kind.

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Tom C

Posts: 287
From:Brodheadsville, PA USA
Registered: Jun 2001

posted February 07, 2004 02:41 PM     Click Here to See the Profile for Tom C   Click Here to Email Tom C     Edit/Delete Message   Reply w/Quote
What you see is a classic problem, usually called die bleed or die drool.

There a two causes I can identify;

Low molecular weight components boiling off at the die exit and condensing at the die exit. Usually black, brown, runny or fuzzy in appearance.

High viscosity material caused by cooling, cross linking or degradation at the internal die walls that slowly extrudes at the die edges. Usually glossy and viscous looking.

The solution is found in controlling the source of the contamination. Please email me for more information.

Tom C

[This message has been edited by Tom C (edited February 07, 2004).]

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