Unless you actually measure the melt temperature, you really do not know what is happening with the material. Recently at a molding facility, we encountered a 65 F (36 C) difference between the melt temperature and barrel temperature.
Comment from Technician: We always have to to run this mold with a hot material to get it to fill. Typically , we have to run the Polypropylene around 500°F (260°C).
Response: When measured, the melt temperature was actually only 434°F (223°C). In reality, this machine as designed with improperly located heater bands giving the impression that the material is actually much hotter than it really is. In fact, the material is being processed at a much lower temperature than most of their other machines.