Only 2% Improvement…?

In response to a recent class, a participant encountered this result…

We have very fast screw recovery times, typically less than 2 seconds. When performing the rear zone temperature study, there was a steady increase in recovery time from 1.78 sec. @ 225°C to a result of 1.82 sec. at 260°C. Does this seem like a valid result?

My Response
This is a perfectly normal result, especially when the screw is properly designed for the application. In actuality, the lower rear zone temperature demonstrates a 2% drop in screw recovery time which usually translates to a 2% drop in the energy required to melt the material.
Additional Thoughts
Screw recovery typically consumes the greatest amount of energy during the molding cycle. A 2% drop in energy consumed during recovery might result in a 1% drop in overall energy consumed… this can become very significant to the bottom line of a high-speed consumer molder.

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