Hi
I need to make 50 cm long carbon fiber octagonal pipe 50mm flat-flat with wall thickness of 2mm, outside surface quality is important. Im looking for ideas how to make it. Currently the best solution i came with is to do vertical vacuum infusion with heat formed pvc pipe as outside mold. If you have any ideas, guidance please share.

You guys must get aluminium a lot cheaper than we do in Aus. I've got prices on a few one-off machined moulds, and something this size you would be looking at AU$2000 minimum - IF the machine shops want to do it at all for less than 5 parts.

Crazy to think composite tooling would cost anywhere near that much, you'd be closer to $200 in materials. More of an investment in your own time sure, but that's generally the case with one-offs. A 2-piece split mould for this would be dead easy to make without any CNC involvement at all.