I have recently been printing gun accessories, (picatinny rails etc.). I have used carbon fiber filaments based on PLA. I have found them to crack easily when the object is thin 1 or 2 mm.
I have been printing a few parts with Polymide PA6-CF. It is a Nylon based carbon fiber but this stuff is very easy to print with. The product calls for a nozzle temp of 280 to 300 but I am printing just fine at 275 which is the most you can get from Snapmaker 2.0 at factory settings.
Bed temp at 40 degrees and blue painters tape.
I used a brass 4mm nozzle. I have tried steel nozzles with mixed results and now I just use brass and toss them once they wear out.
I used CURA to slice with and blocked all supports above a couple of millimeters from the base. This stuff is very rigid and I didn’t want to jack hammer supports off, especially on interior areas. I tilted this mount 15 degrees to try to eliminate as many 90 degree surfaces as possible.
Brim for a platform. It printed great without supports in areas I didn’t think it would.
Print speed 50
Clean up was easy this one snapped off the supports when I start to remove it from the bed. Just had to file a few areas.
You have to anneal it in an oven for 6 hours at 90 degrees (200 F). I just put them on a cookie sheet with parchment paper under it.
Tip: Check with wife before doing this.
After annealing this stuff is like a rock.
PolyMide web site.