Printsettings

designed for ∅0.4 nozzle, 0.08 layer - ironing on. Supports may help with the overhang on the stich retainer (core part) - but shouldn't be essential.

PETg (PCTg) is preferred but i also tested this with PLA.

You may need some post process and sand rough edges so the thread can glide over.

Use lubricant for moving parts.

Coating the stichholder (small fins beside the needle slot) with CA glue (or epoxy) on the outside will increase the strength (best done before assembly).

Preparing the needles

After printing on a flat surface you just fold them - you can add a drop glue if you like.

Inserting the needles one by one at the topmost position (core not clipped in). And use a little grease for the cam groove (PTFE) and needle slots to ensure smooth movement.

After all needles are in, clip the core in by pressing together axially - if you need to open it, use a thread an pull into the gap between ring and core above the grip.. after two or three turns you can pull the parts apart again.

Thread

use a thin (max ∅1mm) semi elastic soft thread - the thread will have a big influence.

Start the thread every second needle for the first turn.

you need to check that the thread is not jumping any needles and is secure under  the retainer fins. Now turn slowly and follow each stich - if you feel a jam use a needle to loosen the stiches a little.

pull the center down and use the weight.