posted November 30, 2005 05:19 PM            

New to the forums. Might stick around here. Seems to be a nice place.

Okay, my problem....I'm working with good 'ol HDPE (15 melt) on Engels and one old Husky machine. The problem I'm running into is: the HDPE is sticking to the screw! I've never seen this before, though I worked at one place for over 15 years...and I've just started working with these Engels/Husky at a new job. But, I've never came across this type of problem before. It is most problematic when the machine(s) have sit for awhile (with the barrels emptied, of course), and then try to start up the machine. In effect, the machine is starved for a shot. I haven't done much investigating on this yet (as it just happened today to me at the end of the workday), but the other techs are aware of the problem, but don't understand why the PE does this.

Anyone have a clue as to why the PE is clinging to the screw?

For info: Barrel heats are profiled (low on the ends (390), high in the plasticizing zones (450)), the feedthroat temp is normal, virgin resin only (with black colorant on this example), barrier & GP screws.

posted December 01, 2005 07:06 AM               

Start with a clean machine and screw. Set the first zone dead cold. Set the other zones around 380F.

Start the machine and check your recovert time. Slowly raise the first zone and watch the reaction of the recovery time. At some point you will reach the optimal point and surpass it. Set the zone back down to the optimal temperature. Run for several hours to see if it will maintain the recovery time.

Whan you have the best data, RPMs, shot size, recovery time, backpressure, post it here and I can calculate whether the screw is running full or not.

------------------
Best Regards,

Tom Cunningham

Extrusion Technical Services