Instructions for replacing the Prusa heatbreak
Hi,
Due to repeated jams with PLA (especially with a .25 nozzle) that matches the symptoms discussed in this thread, I'm going to try replacing the Prusa custom heatbreak with a standard E3D heatbreak. I am researching the correct way to install it, and haven't found a complete set of instructions so I'm compiling a process from multiple sources. I'm new to 3d printing, so I'm looking for some feedback on if I missed anything.
I think I have most of the process down, except for two steps - I'll make them red text in my list below. Basically, I'm unsure about if I should remove the heat cartridge and thermistor prior to separating the heat block/break/sink, or if I need to change the PTFE tube to work with the new heat break.
Here's my plan:
- Heat it up and remove the nozzle- I'm doing this because I'm uncertain if my current nozzle is correctly placed - it might not have enough of a gap between it and the heat block.
- Cool, turn off and unplug the printer.
- Follow the partial disassembly steps for the extruder from this page: https://manual.prusa3d.com/Guide/How+to+replace+PTFE+tube+on+the+MK3S-MK2.5S-MMU2S/1418 (steps 3-5 basically)
- Should I remove the heater cartridge and thermistor, or leave them in and just be careful about the wires during the next few steps? Which is least likely to either break the wires or introduce new problems?
- Separate the Prusa heat break from the heat block and heat sink.
- Reassemble the hot end with the new heat break based on the E3D instructions here: https://wiki.e3d-online.com/E3D-v6_Assembly
- Insert the nozzle back into the heat block, then unscrew 1/2 turn.
- Insert the new heat break (I bought this one) into the heat block and hand tighten until it butts up against the nozzle, then tighten the nozzle a little with a wrench (we'll do a final tighten later when hot).
- Coat the cold end of the heat break with thermal compound. I bought this one: Thermal Grizzly Kryonaut Thermal Grease Paste
- Hand tighten the heat sink onto the heat break/block.
- Is the standard Prusa PTFE tube with the beveled ends still the correct tube, or was it only beveled because of the custom Prusa heatbreak and I should replace it with a straight-cut tube?
- Insert the hot end back into the extruder and put it all back together (steps 9-12 of the first Prusa link above).
- Heat it up and tighten the nozzle.
Any advice about whether or not to remove the heater cartridge/thermistor, or what PTFE geometry should be? Am I missing anything else in my plan, or does this seem like the correct procedure?
Thank you for any advice!
Edit: Regarding the Prusa PTFE tube beveling, what I'm referring to is the conical shape of the two ends as discussed in this article:
https://manual.prusa3d.com/Guide/How+to+trim+PTFE+tube+-+Original+Prusa+i3+printers/500#s18622
RE: Instructions for replacing the Prusa heatbreak
E3d used to say cut the bottom of the PTFE 'square'
Prusa who probably buy most of e3d hot ends say taper the bottom on the outside...
I taper mine. And dont have blockages. You need to decide which is bust. I suggest you consider what shape the drill tip is and whether a square tube end will fit it well.
Taking the heater and thermistor cartridges out, is likely to end in tears...
Also
When you try to remove the heatbreak. You might find it glued into position by the old filament especiakkycif tge nizzke has ever been installed incorrectly. If you still have tge heater and thermistor in place you can heat it up and release the heatbreak.
When assembling theheatblock heatbreak and nozzle i smear the 6mm threads with coppaslip to prevent future sticking. I also use heatsink paste on The 7mm thread that goes into the cold end heatsink. I screw tge heatsink on all the way then again back it off half a turn. Then i push the ptfe in throuhg the black ring. And press the ptfe in whilst ensuringvthat the black ring is pulled back away from tge heat sink. Then ivscdrew the heatsink tge remaining half turn and tighten hand tight. This ensur3s that the ptfe will not move in use. You can now fit a retaining collet under the black ring. But i dont find it necessary.
Now comtinue with reassembly of the extruder module.
Good luck
Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
RE: Instructions for replacing the Prusa heatbreak
As Joan said. Last time I did this my procedure went something like this: I was basically following E3D's procedure - refer to it as I may miss a detail here.
I first heated the hot end to 280c, loosened the nozzle a turn. Then I carefully removed the hot end from the extruder (being careful to not tug on wires). When the hot end was free and dangling, fully removed the nozzle, and unscrewed the heat sink and heat break from the heater block. I had to use pliers to hold the old heat break to break it loose from the heat sink (it came out of the heater block easily).
I did not play with removing the heater or thermistor (danger Will Robinson).
I added heat sink compound to the upper heat break threads (new heat break :~), and threaded it into the heat sink until hand tight. Compound isn't required on the hot side, but won't hurt anything and acts as an anti-sieze.
I prepped the heater block by installing the new nozzle per E3D procdure (out 1/4 to 1/2 turn), and I threaded the heat sink and heat break assembly back into the heater block until it was snug against the nozzle, again, hand tight. The neck of the heat break was flush with the top of the heater block. I also replaced the PTFE with spares from my MK3 kit, made sure it was fully seated and installed a collet clip to ensure it stayed seated.
Reinstalled the hot end and reassembled the extruder bits. Last step was heating the hot end to 280c and torquing the nozzle to 3 nm while holding the heater block with a wrench.
Anyway - something like that. It was easy to do. Main thing is the nozzle tightens against the heat break, not against the heater block. The HEX of the nozzle must not bottom out against the heater block.
RE: Instructions for replacing the Prusa heatbreak
Thanks, Joan and Tim! I appreciate your time and advice.
RE: Instructions for replacing the Prusa heatbreak
I had some time last night and was able to complete this process. I've only had time to do a live Z calibration and one quick print. However, it was a print with a lot of retractions and very thin perimeters that I haven't been able to successfully print with either PLA or PETG using the stock heat break, and with the new E3D heatbreak it just printed flawlessly without any extruder clicking or print failures using PLA. So my initial experience is that the heatbreak was the culprit. I'll update the thread if I learn anything new as I do some more prints, but for now I'm very pleased.
Thanks again for your advice!
RE: Instructions for replacing the Prusa heatbreak
Hi again,
I'm now having a new problem. After replacing my heatbreak, everything has run fine for a day or two, and I've printed several small to medium objects without trouble. This afternoon, I had a new jam. The TL;DR version is that the filament is stuck inside the PTFE tube itself. There was no clog in the nozzle or heatblock/heatsink, there are no visible filament blobs above or below the PTFE tube to prevent movement in either direction, and no clear sign of deformation within the tube, but its like the filament is just glued into place in the tube. I'm replacing the PTFE tube, but have two questions:
1. Any ideas what would cause this? Did I do something wrong when replacing the heatbreak, for example? Is there something I should be doing to avoid a re-occurrence?
2. I'm running low on replacement PTFE tubes from my original spares bag in the MK3S kit, and would prefer not to have to trim/drill the correct bevels; I don't think I have a drill bit that would work for that. But I also don't want to pay $12 shipping for a $0.69 part. Does anyone know if PTFE tubes of the correct length and bevels are sold in the USA?
Anyway, here is a longer description in case you want more details:
I'm using a .25 mm nozzle and PLA filament. I was not at the printer when the jam happened, so I don't know if there was any noise or other indications. When I returned, the top third of the print was missing, and the unfinished top layers were fairly wispy and stringy. There were no obvious issues in the bondtech gears other than dust/grit from grinding the same piece of filament for who knows how long. I'm in a cool basement, so the filament was not soft near the bondtech gears and there was no blob or buildup of filament above the start of the PTFE tube.
I heated up the nozzle to 215, then 240, then 270, and was still unable to get any movement in either direction while pushing or pulling the filament. I next removed the nozzle in case it was clogged, but the nozzle itself was clean and even without the nozzle the filament would not move in either direction. I pushed a brass rod up the nozzle hole into the heatbreak and hit the filament quickly but couldn't move it. If I heated the brass rod first, then pushed into the filament, it would melt a little but still not push.
So I snipped the filament at the bondtech gears, then partially disassembled the extruder and removed the hot end. Everything looks fine, there are no visible blobs/clogs around the heatblock/heatbreak/heatsink. I tugged on the PTFE tube, but the collet was still raised and the tube was firmly in place so there was no slippage there. I lowered the collet and was able to easily remove the tube (and the filament) from the heat sink - the filament was not stuck inside the hot end, it was just stuck inside the PTFE tube itself.
There are no blobs on either end of the PTFE tube. If I hold it up to a light, the PTFE tube is semi-transparent while the filament is not, so I can see the outline of the filament throughout the whole length of the tube, and I don't see anything obviously misshapen. I'll attach a picture of it against a bright background so you can see what I mean. The lower end of the filament isn't in the photo because it broke off while I was trying to force it through the tube, but there was no bulge or blob (and no 2.2 mm bulb either, so at least that worked!). But the filament will not move in either direction through the PTFE tube, so it must be binding inside the tube for some reason.
Thanks for any suggestions you can provide!