InjectionExtrusion Nozzle Refinement

I’ve recently completed the build of my first Injection machine and have had some issues with the standard cast nozzle. I’ve had a lot of ‘dead’ space between the plunger and mold’s gate. This has resulted in a lump of plastic becoming slightly cooler just before entering the mold or sometimes a pocket of air to form between shots. I’ve seen @riceandcarry have been using a nozzle with a built in ball valve as seen in this post. I haven’t tried this method yet and so cannot comment on the efficiency or ease of cleaning. But I have found a to way shorten the distance between the mold and plunger with the use of a threaded socket and hex bush.

I cut the socket and hex bush with a hack saw:

Ohhh I see @riceandcarry, thanks for the clarification. I also like how your molds screw onto the barrel directly… It made me think of doing away with a plumbing nozzle and possibly tapping a thread inside the barrel for mold attachment (unless I were to CNC a mold)

Hi @timslab, Hi @carlf we don’t use the ball valve to connect to the mould. We use it only to block the polymer from sinking down and hardening in between injections. The tap always looks like on the pic. The plastic on it pushes into the heating tube and once taken off only nice and hot plastic will be innjected.
Our moulds are different to yours because they have a build in thread that splits in half when opening. We attach directly to the pipe, no nozzle in between. Both approaches are very recommended. Works really well.

yeah have the same problem… thought about a nother heat modul. But adjusting the nozzle itself sounds better. hopefully i’ll have time in the next weeks to fix it. then i will update in this topic:)

Some early tests in HDPE

After injecting and leaving the barrel to cool, the plastic can be easily removed from the nozzle. The edge of the barrel and the inner bushing almost form a complete seal