The statement "the material is failing in the application and everything is the same.   In fact we have used this same setup for the last 5 years and the same grade of material and never had this problem."

The simple solution is that it must be the material. Nothing has changed but the material, not the grade but the lot number.  As questions would be asked the answers would be vague, don't know, or never measure that. The questions that should be familiar to those whom have followed this column for a few years are:

1- What's the melt temperature of the material?
2- What's the fill time?  Has it changed?
3- What's the steel temperature
4- What's the plastic pressure on pack?
5- Lot numbers and grade of material?  Has it changed?
6- Is anything added to the material and have we tested it when it has been pulled out.

As can be notice, all the questions refer back to the plastic conditions / results. If the results/conditions are duplicated with no change than change lots and see if the problem persists. However, if only going off the machine conditions, than how is it known that everything is the same?

The questions than would be
1- When was the fill time flow control valve last calibrated and certified?
2- When was the last time you measure the flow of fluid through your cooling lines? In addition, does the set up match the master.
3- What is the calibration on the heater bands, backpressure and screw RPM, is the screw recovery the same?
4- Is the packing pressure recorded /set in hydraulic pressure or plastic and what are the intensification ratio and what machine was it run before and what are the data points.
 

As can be noticed the two sets refer back to each other but are in different meanings. The point is that we need to know the plastic conditions.  Can parts be made off just the machine conditions, yes.  … However, it will take longer to dial in when moved to different machines. If using plastic conditions are they more consistent, yes. Can the mold be moved to different machines and the set up is different, yes. Well it take longer to dial in no… based on the fact the plastic conditions are still the same.

The solution to the above statement was to raise both the mold heats and the temperature settings on the barrel. Did they than take the melt temperature or mold temperature so they had a reference, no.  Hey we have good parts and are okay now.

Thanks for the time

Steven L Silvey
Sr. Technical Service
General Polymers Division of Ashland Distribution