@Kevin_Danger_Powers Typically people either stop the PTFE tubing above the cold zone (all-metal designs) or bring it all the way to where the nozzle starts to throat down to the tip (PTFE-lined designs). If the PTFE liner ends where the nozzle threads start, you can leak molten filament into the gap between the PTFE and nozzle and get bad problems. You can make it work, but my understanding (without personally owning a J-head) is that it’s going to be sensitive to the length and cut on the PTFE tube to get to where thermal expansion of the PTFE kind of seals off the tip of the tube from filament leaks, without expanding so much that the PTFE tube actually buckles from thermal expansion and crimps halfway shut. (Yes, that can happen.)
@Ryan_Carlyle well designed all-metall hotend where to buy have you a link?
@Ryan_Carlyle that makes sense. Thanks for the info. I’ll have to try and see what happens I guess.
@Kevin_Danger_Powers Oh, and it’s really important that the internal diameter through the entire bore from top to bottom is only slightly larger than the filament diameter. IE for 1.75mm filament there should be no part anywhere that is larger than 2.15mm, and more like 1.95 is preferable. So I’m confused when you say you had a 3mm ID tube… are you putting 1.75mm filament in a 3mm filament hot end?
@Ryan_Carlyle no, the tubing that came with my printer has an OD of 4mm and an ID of 3mm. I’m using 1.75mm filament so there is a lot of slack. I actually just tried replacing it with tubing that has a 2mm ID but it kept getting pulled out because there wasn’t enough grip on the tube.
@Kevin_Danger_Powers Bowden tube (between extruder drive and hot end) or feed tube (between spool and extruder drive)?