Heater unit / PTFE Tube
Hi *,
I had to take apart the hot-end to remove some PLA, which broke below the extruder gears.
(My tries to push the filament through were futile.)
Disassembly and removal of the filament felt ok to me, but as this is the first time I've experienced such a blockage I don't have any experience to determine, whether I did something wrong. FYI, I had to heat up the heat break, as well as the heat sink to soften up and remove some PLA which had formed a blob below the PTFE tube.
I also realized, that the PTFE tubing could not be removed towards the top (ie in the direction away from the nozzle), even when pushing down the collet (the black ring on top of the heat sink). I could push it down and after removing it from the heat sink, I realized that there is a small thicker portion of the tube that limits it movement upwards.
My first question is: is this thicker portion normal with the Prusa version of the hot end? It certainly looks like it was machine-made and not the result of melting PTFE (I also assume that I did not heat up the heat sink to the melting point of PTFE, as the PLA came out soft, but not melted.)
After cleaning everything, I re-assembled the hot-end following the information on the E3D dozuki, so
I tested the hotend (with the cooling fan) - it heats up ok, thermistor seems to report correct values and pushing filament through by hand works again.
So now before I re-assemble the complete extruder/hotend I'd like to ask for you suggestions on how to proceed. Do you have any tips for me?
---- EDIT ----
I just found http://manual.prusa3d.com/Answers/View/645/Length+of+PTFE+tube+included+in+kit. .
Event though this question applies to the MK2S, I assume that the hotends are the same.
The thicker portion of the PTFE tube seem to be normal.
So the question now is: Do you have any suggestions of how to apply enough torque on the heat sink without damaging the heat break?
---- EDIT ----
Thanks and kind regards
Andreas
Re: Heater unit / PTFE Tube
Don't see this thicker end on the PTFE tube in my MK3.
It is just a plain piece of PTFE tube with the bottom (the part above the heatbreak) slightly beveled.
Re: Heater unit / PTFE Tube
The lower end of the PTFE tube should be both chamfered and tapered.
Rather than disassembling the hot end, try this:
Heat the hot end to 25 degrees more than the usual extrusion temp
Wait 10 minutes
Undo the tensioning screws and open the door containing the secondary drive pulley
Push fresh filament from the top
FWIW, PTFE is OK up to about 255 degrees.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Heater unit / PTFE Tube
First of all, thank you for your suggestions and the information on the PTFE tubing.
Coming back to my original questions: Do you have any tips on re-assembly?
Re: Heater unit / PTFE Tube
The lower end of the PTFE tube should be both chamfered and tapered.
Rather than disassembling the hot end, try this:
Heat the hot end to 25 degrees more than the usual extrusion temp
Wait 10 minutes
Undo the tensioning screws and open the door containing the secondary drive pulley
Push fresh filament from the top
FWIW, PTFE is OK up to about 255 degrees.
Peter
DO NOT WALK AWAY DOING THIS. I'm sure that if you left it on for 30+ minutes like this, you could cause damage to the printed parts.
Depending on the brand. It's good from 230c up to 280c. I would guess prusa's white would be around 250 however. (It is fairly good quality)
I however agree with this method. Just be careful, as you are essentially deliberately creating massive heat-creep.
(I wish the extruder was easier to service. One of the big reasons I am running JLTX's Skeletruder)
Hi, I'm Sean. I used to work on CNC machines.
I try to not make mistakes, but the decision is YOURS.
Please feel free to donate to my filament/maintance fund.