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  Problem With Powdered PVC Lubricant on 1st Downstream Vacuum Sizer Causing Jamb-ups

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Author Topic:   Problem With Powdered PVC Lubricant on 1st Downstream Vacuum Sizer Causing Jamb-ups
XtruDR
Member

Posts: 1
From:MN USA
Registered: Feb 2007

posted February 28, 2007 01:14 PM     Click Here to See the Profile for XtruDR     Edit/Delete Message   Reply w/Quote
Having problem with powdered PVC lubricant on 1st downstream vacuum sizer causing jamb-ups.

Extrusion is a rigid PVC profile on a vented Krauss-Maffei KMD-90 vented twin-screw. Die and tooling were designed to run at 415F to get speed necessary for profitability -- however, powdered PVC material is rated at 390F max.

Intriguing thing is that sometimes the system can run a week without a jambup, next time it occurs every couple hours.

Have looked at all available data in KMD-90 C4 controller, but do not see any anomalies that could be correlated to jambup frequency.

Am considering looking at powder chemical and physical properties and particle size and consistancy.

Any guidance on where or what to look at would be appreciated!

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XT12UDE12
Member

Posts: 1
From:PA
Registered: Aug 2007

posted August 25, 2007 12:05 AM     Click Here to See the Profile for XT12UDE12     Edit/Delete Message   Reply w/Quote
Assuming that there are no material issues, after the first jamb-up do you open the vacuum sizer to check for any obstructions? In my experience after running a profile for an extended period of time (4 days to a week) a waxy buildup forms in the vacuum slots in the sizer.Without clearing these slots you will be prone to more frequent backups. Some materials leave more wax than others. I run one material that clogs a sizer twice as fast as another simply because it is missing an impact modifier.

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