I do not completely understand the whole system that you are considering but my first thought is to carefully predry your nylon as it takes up water readily and that can give bubbles.
We overmolded nylon over electric motor coils. Yes, drying is the answer. Another is to inject from thick to thin sections. Chose your point of injection carefully.
we are using direct gating and are drying the nylon - it is nylon 66.
It is a 16 cavity overmould situation and all cavities seem to be affected.
What about vacuum in the cavities ?
A vacuum is a good idea that will allow you to have faster injection time, no problem if the tool has some venting issue’s vacuum will take care all that. However, it will not help you at all if your polymer is wet at the time of the injection, or if you have any of the problems that were mentioned to you by the other members.
