This question arrived as a follow-up to a previous post: More About Back Pressure…
If I have to work with an odd back pressure like 250 bar, does it create any damage to the equipment or machine?
Assuming this is the plastic pressure, this would not necessarily cause machine damage. This will consume a large amount of energy and create a large amount of shear during recovery. The potential for material and additive degradation may be high depending on the material being processed.
You may wish to consider a new screw designed specifically to address the complication you are encountering during recovery. For instance you may need a longer transition zone if the shear is necessary for melting, or you may need a mixing element in the metering zone if the back pressure is used for additive mixing.
This may be great application for a shot-pot style of molding machine. This would allow a properly designed material-specific screw to be used to melt and convey the material while a plunger is used to inject the melted polymer.