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Author
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Topic: lines in sheet
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jackie
Senior Member Posts: 14
From:Newcastle England
Registered: Oct 2003
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posted May 19, 2005 03:37 AM
  
I am running Apet sheet on my OMV co-extruder things look fine until I try to increase output and lines start to appear in sheet. Initially thought they were coming from Co-Ex as when turned off lines disappeared but after cleaning they were back. Thought it might be something to do with pressures so reduced pressures on main line and Co-ex and this seemed to help. I need to icrease output can anyone help.Jackie. IP: Logged |
Steve H
Moderator Posts: 367
From:New Zealand
Registered: Jun 2001
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posted May 19, 2005 04:09 AM
Could they be moisture tracks Jackie, if you've upped the through put, maybe your dryers arn't keeping pace.------------------
Steve Hodgson If at first you don't succeed, skydiving is not for you. IP: Logged |
jackie
Senior Member Posts: 14
From:Newcastle England
Registered: Oct 2003
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posted May 19, 2005 07:20 AM
Lines come and go within 5/10 mins I would guess if it was the dryer it might take longer to show ? Is it common to get moisture lines ? Moisture seems to come through more as pit marks in sheet in my caseThanks for your Interest Steve IP: Logged |
Tom C
Moderator Posts: 572
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted May 19, 2005 12:30 PM
Jackie,It is very common for extrusion processes to pass more unmelted material to the die as the screw RPMs are increased. Depending on your die design and sheet thickness the unmelted materials could get stuck in the die and produce a line until they eventually melt. Please contact me directly at 570-992-0961 if you think you could use some professional consultation in resolving this issue. I have many tools at my dispoal which can help develop extrusion productivity. ------------------
Best Regards, Tom Cunningham Extrusion Technical Services
www.ExtrusionTechnicalServices.com [This message has been edited by Tom C (edited May 19, 2005).] IP: Logged |
jackie
Senior Member Posts: 14
From:Newcastle England
Registered: Oct 2003
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posted May 20, 2005 10:29 AM
Tom sounds like it could be what you have said makes sense. Would increasing die temp help or do I need to go right back to the barrel ?
Thanks Jackie.
IP: Logged |
joeex
Member Posts: 2
From:Durham
Registered: May 2005
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posted May 20, 2005 10:56 AM
Jackie
Is your die lip to tight and is the material coming out serrated from the die. What happens if you turn off the co-ex and up the line speed ? Cheers Joe..... IP: Logged |
Tom C
Moderator Posts: 572
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted May 20, 2005 06:59 PM
Jackie,A quick fix may be to add screens to the breaker plate, or use a tighter mesh screens. Sometimes screw and barrel wear can be the source of unmelted resin. A better solution would probably be a new screw design. There are lots of interesting options depending on your application. I could refer you to a couple of capable companies in England if you wish. ------------------
Best Regards, Tom Cunningham Extrusion Technical Services
www.ExtrusionTechnicalServices.com [This message has been edited by Tom C (edited May 20, 2005).] IP: Logged |
jackie
Senior Member Posts: 14
From:Newcastle England
Registered: Oct 2003
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posted May 23, 2005 06:16 AM
Thanks for your interest Tom I will try a different mesh. The srew I have in is only 4 months old and was made in UK by Stanley Vickers to an OMV Apet design so am hoping that it is OK.Thanks again Jackie. IP: Logged |
Tom C
Moderator Posts: 572
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted May 23, 2005 08:03 AM
Jackie,If you continue to have problems please email me if you are interested in my assessing your screw. tomcun@ptd.net
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Best Regards, Tom Cunningham Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
jackie
Senior Member Posts: 14
From:Newcastle England
Registered: Oct 2003
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posted May 24, 2005 11:46 AM
Tom, Thanks again for your help have tried extra mesh screen to breaker plate and first impression is it is looking good will let you know how I get on after extended trialJackie IP: Logged |
Tom C
Moderator Posts: 572
From:Brodheadsville, PA USA
Registered: Jun 2001
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posted May 25, 2005 10:55 AM
Jackie,I should have added that you need to keep an eye on your pressure rise over time, because unmelted material my clog up your screens. You should also check your product microscopically for small unmelted particles. Their presence can dramatically weaken the sheet. ------------------
Best Regards, Tom Cunningham Extrusion Technical Services www.ExtrusionTechnicalServices.com IP: Logged |
michman
Member Posts: 1
From:Holland, MI / USA
Registered: Aug 2005
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posted August 12, 2005 02:52 PM
Jackie,
A high die temperature can result in contaminates seeping through a restrictor bar seal, Do you have teflon seals?IP: Logged |
