posted August 21, 2002 03:30 PM               

Am I right in assuming that your gear pump controller is controlling screw speed also, so as you ramp up the melt pump RPM's, screw speed is increasing. Are you flood feeding the screw?

With a small diameter screw you are much more dependant on putting heat into the material from the barrel heaters.

If the line has worked ok in the past and has just started to shear pins all of a sudden, then I would check:

(1) Barrel Zone heaters and controllers

(2) Raw material, maybe your supplier was supplying material at the top end of his melt flow spec and has "improved" something in his process and is now supplying material that has a much lower melt flow than you've gotten used to.

If this has always been a problem, then you have to look at your screw design. A short term cure could be to raise the temperature of your incoming feed material.

posted September 06, 2002 02:11 PM               

quote:

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Originally posted by mitch:
I am experiencing allot of shear pin breaks on a 3/4" extruder with a 0.16cc melt pump. It happens randomly during a run or when I am ramping up to higher pump rpm's. I am running Pebax at about 210 degrees C. I am loosing allot of production time because of this.
Any suggestions on the root cause.

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