This seems like an extruder design flaw on the Printrbot Jr.

This seems like an extruder design flaw on the Printrbot Jr. I’m sure it worked fine with 3mm, but not so with 1.75mm. With so much room to move around on all sides, particularly the left and right, I believe this is the culprit (at least in large part) of my jamming issues. I’m probably going to take the thing apart and see if I can glue some shims in there.

il a vraiment un problème de conception dans l’extrudeuse a voir sur Reprap : le point sur les extrudeurs
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@John_Schneider That sucks! I’ll have a look at mine this weekend and see what happens. Its almost like there needs to be a square insert with a 2mm hole drilled through it slotted into the filament channel of the extruder. Something slippery and can withstand a little heat would be best, like ptfe, but maybe nylon or even acrylic or wood would work.

@John_Schneider You are not alone!
First extrusion out of the gate (haven’t fully buttoned things up yet) and it jammed after maybe 30mm extruded. That new cartridge heater hot end seems like its heating way up into the cold end. It holds its temperature fantastically, props to @Printrbot , but did they test the LC extruder with a variety of 1.75mm filament or did they just start shipping? Seems like a machined nylon or ptfe insert 6mm thick with a 2mm hole that can sandwich inside the extruder between the hobbed bolt and cold end is called for. Keep the filament supported during extrusion and be slippery enough not to increase friction. Either that or go back to a printed Wades. That sucks. I’ve got some nylon sheet I could try but I’m probably not going to have much more time to work on it before next weekend… keep me in the loop if you find a solution.

Will do. @Brook_Drumm any thoughts or input on the issue?

Hi John, thanks for the hint. My Jr. has a 3.5mm hot end. However in the next few days I get an additional extruder with the new 1.75mm Ubis hot end for testing. Let’s see how we can solve the problem:-). Happy printing, Max

@John_Schneider Got mine to work using your suggestion… I had some 5mm OD 3mm ID ptfe tube laying around, took out the hobbed bolt, and squished the tube down the filament path. Had to flatten it a bit to fit so its not perfect but it seems to do the job. Cut it flush and started printing. I’ll try to get some photos and details posted this weekend.

@Brian_Evans , I just got done doing something similar, but I drilled out the hole in the extruder since my PTFE tube was 6.35mm OD, 3.16mm ID. I’m doing my first print since the mod right now, though it’s not going to be a very challenging print. I’ll try something that I had difficulty with before later tonight and let you know how well the mod worked.