Buzz: Oh yes, Skippy; another thought on the discussion so far about extrusion screw and barrel wear and "surging".
As you know, we have been involved with extrusion companies in two broad camps -
a) those that religiously measure and rebuild screws and replace barrels when they expect wear to be too much of an impact on reliable extrusion, and
b) those that have machines that you can rattle the screws around in worn barrels to a good degree
and yet because they can continue with process updates and changes produce product profitably, these companies couldn't care less about the thought of "measuring the wear" and moving directly to repair/replacement.
Skippy: - but how can this be? If both can achieve steady state extrusion with a wide variety of virgin and regrind materials in new and worn equipment, and both can exhibit machine conditions where "surging" exists - there must as Paul Harvey says be a "the rest of the story" -
Buzz: well yes. We have some thoughts on this that we would like to share with our readers and use to develop some discussion on solutions as well as discuss why this TYPE of question is so difficult - once we've had a little tryptophan er um TURKEY to help marshall our thoughts, we shall continue.
Skippy: - what direction is the discussion likely to go?
Buzz: well, I'd like to see us confirm that there is essentially no right or wrong answer here, but due to the system or environment in which it is answered, it could go either way.
BECAUSE of that, perhaps it is time for us to spend a few sessions in a much more compressed time span talking about a number of the other extrusion variables that can contribute to "surging" as well, how to spot them, how to eliminate or at least control them, and certainly the importance of being aware of them. In this way, our readers hopefully will jump in with additional thoughts and our dialog will be that much more productive -
Skippy - can't wait - see you in a day or two . . . Happy Thanksgiving to all!
(to be continued)