I made these in a pinch and they work remarkably well.

I recommend printing them with support, I printed 4 without and the tips are warped because of it. The 5th I printed with support and the tips look perfect.

All the needles needed some sanding as to not catch the yarn. Maybe a lower layer height is better, but I wanted them fast so I printed them at 0.20 mm. They work well for knitting in the round as they are smooth enough to allow for knitting, but not so smooth that the pens fall out of the stitches. 

I'd say these are comparable to wooden needles.

If you print them, I'd love to see what you make with them!!