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Injection Blow Molding issue

Injection Blow Molding issue

Injection Blow Molding issue

I am having an issue where our injection blow molder will build a shot but when we extrude it it takes 8-10 seconds (out of 15 seconds for a shot) for any resin to come out and it only extrudes about 4" of material when it should be 16" or more.. All our process parameters are set and verified. We have played with back pressure and its made no difference. The crazy thing is delay from when the screw goes forward to when plastic comes out.

We have pulled the screw and cleaned it, pulled the head apart and cleaned it. The screw has some wear on it. However, it was making good parts and in one shot stopped. It wasn't a gradual decline in performance. If it was screw wear I would think it would be a gradual issue.
Does anyone have any ideas on where else to look? I hate to spend money on a new screw when I'm not convinced that is the issue. Any advice would be appreciated.

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