I started down the DIY injection tool path and I got a bit stuck. I got as far as cutting simple shapes with the tiny tooling but never quite figured out the software.

It's the tiny tooling that puts in the fine detail which I found tricky, once you get down to sub mm you have to creep along and pray. You can't see what is happening because you are pumping in so much cutting fluid to clear the "chips" and keep it cold.

I ended up with a modified Roland CAMM-3 but I'm not sure that is the tool for the job.

I got a severe attack of confidence before I understood the problem.

I presume you are planning to inject at the mould break line rather than use a sprue?

Have some links...

Blackburns Metals Limited - Mould Plate - Alumec
DMS-Diemould | Serving mouldmakers, moulders and diecasters worldwide
Berger Tools