Printable PTFE linear bearings for 8mm rods and 4mm ptfe tubing.

I designed these new linear bearings for when I assemble my new steel prusa. I didn't want to wait for IGUS bearings so I never bothered with those. The benefit of these bearings over the usual ball bearings is that they can be made at home, weigh a lot less than the usual alu bearing blocks, are quieter and can be readjusted many times as the PTFE liners wear.

Insert three 4 mm diameter and