Do you REALLY know your melt temp?


During the past few weeks I was in three different countries and five molding shops. I'm always asked to look at some problem. One of the first things I do when I'm in a molding shop is ask if the molder has the material spec sheet and if he is molding the material at the proper temperature.

Interestingly enough, each shop proudly showed me the technical data. Sadly, they all pointed to their machines, noted the temperature on the heaters and pronounced it to be the material's melt temperature. Really?

The melt temperature is only slightly controlled by the heaters. The primary determinant of melt temperature is the screw and back pressure. Why this is a less-than-commonly-appreciated/known fact is beyond me.
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