Maro Publications

Extrusion Dies

Notes

Patent Abstracts

Patent Titles

*10/21/2013 
from 8/19/2013

Maro Encyclopedia

Extrusion

Molds

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Notes

ďAt the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants in the melt. The screens are reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5000 psi (34 MPa). The screen pack/breaker plate assembly also serves to create back pressure in the barrel. Back pressure is required for uniform melting and proper mixing of the polymer, and how much pressure is generated can be 'tweaked' by varying screen pack composition (the number of screens, their wire weave size, and other parameters). This breaker plate and screen pack combination also does the function of converting "rotational memory" of the molten plastic into "longitudinal memory".

After passing through the breaker plate molten plastic enters the die. The die is what gives the final product its profile and must be designed so that the molten plastic evenly flows from a cylindrical profile, to the product's profile shape. Uneven flow at this stage would produce a product with unwanted stresses at certain points in the profile. These stresses can cause warping upon cooling. Almost any shape imaginable can be created so long as it is a continuous profile.

The product must now be cooled and this is usually achieved by pulling the extrudate through a water bath. Plastics are very good thermal insulators and are therefore difficult to cool quickly. Compared with steel, plastic conducts its heat away 2000 times more slowly. In a tube or pipe extrusion line, a sealed water bath is acted upon by a carefully controlled vacuum to keep the newly formed and still molten tube or pipe from collapsing. For products such as plastic sheeting, the cooling is achieved by pulling through a set of cooling rolls.

 Sometimes on the same line a secondary process may occur before the product has finished its run. In the manufacture of adhesive tape, a second extruder melts adhesive and applies this to the plastic sheet while itís still hot. Once the product has cooled, it can be spooled, or cut into lengths for later use.Ē

(Extrusion, Wikipedia, 8/19/2013)

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Patent Abstracts

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Patent Titles

10/15/2013

7. 8,555,693 
Method for forming hollow profiles 

9/3/2013

6. 8,522,592 
Forming apparatus for forming extruded hollow section 

8/13/2013

5. 8,506,282 
Die and die device 

4. 8,506,280 
Lip adjustment system having cross-bar

7/30/2013

3.  8,496,460 
Pipe extrusion die flow path apparatus and method 

7/23/2013

2. 8,491,296 
Lip drive part for T-die 

5/7/2013

1. 8,435,025 
Honeycomb extrusion die apparatus 

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Interested!!
Bookmark this page to follow future developments!.
(RDC 7/16/2012)

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Roger D. Corneliussen
Editor
www.maropolymeronline.com

Maro Polymer Links
Tel: 610 363 9920
Fax: 610 363 9921
E-Mail: cornelrd@bee.net  

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Copyright 2013 by Roger D. Corneliussen.
No part of this transmission is to be duplicated in any manner or forwarded by electronic mail without the express written permission of Roger D. Corneliussen
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* Date of latest addition; date of first entry is 8/19/2013.