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Q: Plastic Extrusion - Extrusion foaming of PP profiles ( Answered 4 out of 5 stars,   1 Comment )
Question  
Subject: Plastic Extrusion - Extrusion foaming of PP profiles
Category: Science > Technology
Asked by: eytan-ga
List Price: $20.00
Posted: 22 Apr 2002 21:54 PDT
Expires: 29 Apr 2002 21:54 PDT
Question ID: 3039
1) Were can I find operational paramenters for extrusion of foamed profiles 
made of PP?
2) In a foamong extrusion process that I try, I get breakage in corners of the 
profile, probably resulting from excess melt sheer forces inside the die, how 
can this be avoided?
3) who can help me design a die for such process?
Answer  
Subject: Re: Plastic Extrusion - Extrusion foaming of PP profiles
Answered By: missy-ga on 25 Apr 2002 21:55 PDT
Rated:4 out of 5 stars
 
Hi there!

A search on ["foaming extrusion process" parameters]led me to a
comprehensive plastics processing site, Feed Screw Designs.com.  You
can get parameters for foaming extrusion processes using the drop down
menus at the upper right of the page.  Select Polypropylene and
Extrusion, and the screw size to obtain specific parameters.
[http://www.feedscrewdesigns.com/]

The site also includes other plastics processing resources, including
a series of forums for both processing specific and product specific
questions.  You should be able to get an answer for part two of your
question there.
[http://www.feedscrewdesigns.com/cgi-bin/forums/Ultimate.cgi]

Searching on ["profile extrusion" custom dies] turns up several
possibilities for custom designed dies:

Custom Plastics.com [http://www.custplas.com/extrude.htm]
A&B Plastics [http://www.abplastics.com/machine.html]
Twitchell Profiles [http://www.twitchelltextilene.com/prod04.htm]
Product Tool Engineering (select "Design and
Manufacture")[http://www.productool.com/]
VKM Tool and Die [http://www.vkmtool.com/]
NovaTec Plastics [http://www.novatecplastics.com/company.html]


Thanks for your inquiry!  I hope this helps you solve your problem.

Request for Answer Clarification by eytan-ga on 27 Apr 2002 07:19 PDT
The answer list some commercial sites, containing poor data.

I got the same answer in a simple google search
The major part of my question was't addressed.

I need a solution to my problem, and unfortunettly couln't find it in your answer.

Can you gather more data?

Clarification of Answer by missy-ga on 27 Apr 2002 11:37 PDT
I assume that the main portion of your question is how to prevent
profile breakage, then?  If so, I will need more information, as
searches through various engines on [corner breakage profiles],
["foaming extrusion" profiles breakage] and ["prevent breakage"
"foaming extrusion" profiles] yield only the suggestion that perhaps I
meant "forming extrusion", and pages about how one prevents breakage
of profiles during shipping, not during manufacture.  Could you
perhaps give me the specific name of the process you are using, to
help me narrow the search and find pages more applicable to your
problem?  (Please keep in mind, I can only point you to general
information - Google Answers is not meant to substitute for sound
professional advice.)

Regarding the list of places who can help you design a die for your
process:

The list in the original answer is not meant to address the breakage
problem, only to offer a list of services who will, as you asked,
"help [you] design a die for such process".  You would have to contact
one of these professionals with your technical specifications to
determine whether they could help you design the die you require.  If
you require a person or business in your area, I will be happy to
search for you,  I will just need to know where you are located.

Request for Answer Clarification by eytan-ga on 28 Apr 2002 22:58 PDT
We assume that the reason for the breakage is excess foaming that
occurs in high shear forces along the die's land (current die lend is
1.6", we need this relativelly long land, as we want the bubles to be
nucliated inside the land).
The shear forcess stimulate buble nucliation at certain locations of
the profile, resulting in a very thin, foamy wall, which causes the
breakage.

I hope that now you have better tools to focus the search, and
appreciate your efforts so far.

Regards,

Eytan

Clarification of Answer by missy-ga on 29 Apr 2002 17:25 PDT
My apologies, Eytan, I don't think I was clear enough in the
information I need from you.

In order to concentrate my search on your behalf, I need to know the
name of the exact process you are using.

"Foaming extrusion" seems to be the general term for a host of
processes, and as I mentioned before, I have been unable to find
information dealing with prevention of breakage during manufacture,
only prevention of breakage during shipping.

I suspect you may need to consult a plastics professional for the
exact answer you're looking for, but I will be happy to search for
general information pertaining to your specific process if you will
give me the exact name of it.

Clarification of Answer by missy-ga on 30 Apr 2002 18:17 PDT
Eytan, 

On a hunch, I posted your problem to the Forum at FeedScrew.com.  The
wonderful professionals there had this to say about your breakage
problem:

"It seems as if the client has asked and answered his own question. If
shearing causes the problem, reduce the shearing. Some remedies common
to all plastic processes are:

1) Lower the shear rate by slowing down the process.

2) Lower the shear stress by lowering the apparent viscosity.

2a) Pick a lower viscosity resin.

2b) Pick a resin that shear thins more.

2c) Raise the resin melt temperature.

2d) Lubricate the resin.

3) Redesign the die to lower the high shear."

They also suggested that if you need further assistance, to try
searching here:
[ http://www.knovel.com/ ]  

Knovell.com has electronic versions of many plastics references, as
well as the complete collection of all of the papers presented at the
last *four* Annual Technical Confrences of the Society of Plastics
Engineers.  A subscription is required to access the full texts, but
the search function is free to all and should serve as a good request
list at your local or university library.

I wish you luck with your project!

Regards,

missy-ga
eytan-ga rated this answer:4 out of 5 stars
I researcher missy-ga did a very good jobn and didn't give up.
I wasn't satistfied by the first answer (apparentlly, my questions
wasn't well defined), so missy repeated answering and asking for
clarifications, till I got full answers. Thanks!

Comments  
Subject: Re: Plastic Extrusion - Extrusion foaming of PP profiles
From: lazerdog-ga on 02 May 2002 10:47 PDT
 
i'm not an expert, but i use to set up extrusion machines at a plastic factory.

usually if you are getting a bad piece the problem is the heats or the material.

who designed the mold?  don't they have a set of parameters?

try to vary the cycle time.  if you are using a foaming agent you have to look 

out for moisture.

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