Hey there,
I've made several injection molds for a swimbait that I've designed(along with a creature bait mold) and I keep having this problem no matter what I'm trying. I tried pushing plastic fast, slow, medium, holding pressure, keeping the injector in the injection hole until I see all air bubbles pop out of the vent holes, then I top off the injection hole, etc. I keep getting an air pocket close to where I'm injecting the plastic from my injector. I have a 6oz injector now, so running out of plastic isn't the issue. I've included a crude diagram to show what I'm talking about.
The diagram shows a side view of the mold. What I also did was make vent holes coming directly from the eye sockets after I discovered the air pocket after doing 3-4 injections. The plastic does come out of the vent holes, but the air pocket still remains. I get a complete injection sometimes, but when that does happen, I get some weird deformity on the top of the head to where it looks like the plastic was sucked in a little.
Thanks in advance!