PTFE tube replacement guide - issues I had with PTFE tube after install  

PTFE tube replacement guide - issues I had with PTFE tube after install

Hi Guys - (everything is back together and seems to be working fine - but after disassembling the hotend multiple times to get it to work is a bit frustrating - that information like what I am about to share was no where to be found - unless I missed it of course.)

I followed this:
https://help.prusa3d.com/en/guide/how-to-replace-a-ptfe-tube-mk3s-mk3s-mk2-5s-mmu2s_21664

Problem 1: You cannot pullout the PTFE tube
Problem 2: After replacing the tube filament starts flowing - print looks fine - then stops about 10-15 mins into it
Problem 3 - 4: Filament would not load into heatsink and was getting stopped by top of PTFE tube
Problem 5: Filament would not slide easily in PTFE tube and gets stuck at end

Taking the time to write this with hopes it will help someone else. To make a long story short - I had to fix a leaky hotend - I had to disassemble the unit to make sure the heatbreak and block and nozzle and sink all were adjust appropriately. (made sure there was a .5mm gap between nozzle and heatblock .etc) while I was in there I noticed the PTFE tube looked a bit worn, so I decided to replace it.

#1

After disassembling the hotend- the help instructions showed PULLING OUT THE PTFE TUBE from the top where the black collar is. You supposedly hold / push the collar down and pull the tube out - this did not work. Pushing the tube from the top - allowed the tube to come out from the bottom - and when doing so you can see why pulling did not work - the tube also formed a beveled protrusion around the end about 7mm in from the exit tip. (pics at bottom of post) preventing it from being pulled.

#2 OK tube is out - new tube in (that came with the replacement prusa parts) - help guide just says to insert it - with rounded narrow end towards hot end - does not say if it should be trimmed, or how much should be sticking out the top / bottom - so I left it as is with about 2mm sticking out the top which seemed to be perfect because it fit in the assembly like that just fine.  I re-assemble, calibrate and print.
t started to print a benchy and about 15 mins into it - filament stops flowing I assume the filament is getting stuck in the PTFE tube, you hear stepper motor clicks on and off from the feeder.  I stop the print and disassemble again and check everything - I unload the filament and reload and with the filament tension door open notice the filament now won't go any further than the top of the ptfe tube area - a little force allows the filament to go in. (seems it was getting caught at the top of the tube)

#3-4 this time after assembly the filament won't load - it starts to load and then as it gets to the top where the PTFE tube - the stepper motor starts clicking. I disassemble again and this time also take a piece of filament to test any resistance in the tube and see that the filament won't go all the way through the tube - the end of the PTFE tube closed to a point not allowing filament to go through. (was the PTFE tube to close to the heatbreak and it started to melt and form the shape of the heatbreak entry hole) see pic in post

#5 - I take a brand new tube and do the same thing as above - but this time I noticed the filament would not slide easily in the new tube and was getting caught slightly at the end of the tube. I took a small drill bit and drilled the inside of the tube top and bottom and took an xacto knife to widen the top and bottom of the tube holes - the filament now loads easily and my prints are working.

WHY DID I HAVE TO GO THROUGH ALL OF THIS - did I do something wrong, did I miss a step ? 🙂

Thanks