45° or 60° cut, 50mm length (MK2/MK3), 44.2 mm length (MK3S), standard PTFE tube 4mm OD, 2mm ID. If unsure which one to use, follow the Prusa instructions (https://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+Original+Prusa+i3+printers/500?lang=en) or use your own judgement according to your need and experience.
The jig is a remixed version of this design (https://www.thingiverse.com/thing:2908391), thanks.
The jig uses 0.5mm thick blades. Source from the original design just for reference:https://www.amazon.com/Soft-Grip-Snap-Off-Utility-Knife-Blades/dp/B003RXMQUY?tag=tv-auto-20
Clean up any printing artifacts (stringing, seams, etc) with the blade before you do any cutting.
The jig needs about 70mm PTFE tube to work, however if you have longer stock, you don't have to cut a 70mm piece. Although tedious, its possible to cut the tubing without any excess.
Rubber gloves will make your life a lot easier while handling the PTFE.
Make sure the PTFE tube is cut flat and clean, in case it isn't you can use the jig to cut some excess. Insert the tube few millimeters past the first cut opening (so it rests on both sides of the cut opening). While keeping that positioning, bend the remaining PTFE tube so it pushes up against the jig and doesn't move while you are performing the cut. Don't over do it, slight bend is enough.
Remove any excess tubing and fully insert the PTFE. Ensure it is resting flat on the printed part while starting the 45° cut. Push and hold the PTFE against the plastic part (you just want to make sure the PTFE doesn't move when you make the initial cut).
Insert the blade and make the initial cut. Grab the tubing outside of the jig and rotate it a full circle (against the blade) while still pushing the tube against the plastic part. The blade should be flat against the plastic. Any imperfections can be cleaned up by repeating the process with light pressure against the plastic part with the blade inserted.
- Clean up any shavings from the previous cut and reinsert the tube again, hold the PTFE gently pushed against the plastic part. Use the cutout on the jig to exert pressure on the tube and rest the blade on top of tube before you cut. Make sure the blade is somewhat straight (the plastic part should guide it). Make the full cut in one motion, don't try to cut it like bread.
STEP files are included for your modding pleasure and convenience. STL files were sliced and checked with Slic3r PE.
Any constructive feedback is welcomed.
EDIT (17/11/2018): Added a version of the jig according to the new Prusa instructions for cutting the PTFE tube (https://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+Original+Prusa+i3+printers/500?lang=en), which instruct to chamfer the outside of the PTFE tube for the extruder at 60° rather than the former 45°
EDIT (12/02/2019): Added 45mm length cut for both 45° and 60° versions. Intended for the MK3S extruder.
EDIT (23/04/2019): Replaced the 45mm length version with 44.2mm one to better match the Prusa Research recommendations
Tested with 3 perimeters, 15% infill, 0.2mm layer height, PETG.
That's the material I had primed up, does not mean that the print need to be from PETG.