this post was submitted on 13 May 2025
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17
Help please: heating block gooed up with PLA (slrpnk.net)
submitted 12 hours ago* (last edited 12 hours ago) by Prunebutt@slrpnk.net to c/3dprinting@lemmy.world
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I got a new Biqu H2V2 for my Ender 3 pro , since myold hotend started getting unreliable and that was a great excuse for yet another upgrade.

I wasn't happy with the carriage holder I printed, so I wanted to print a new one. After afew hours of printing, I needed to abandon one part, since it was incredibly messy with blobs of PLA gooped on the print. Since I needed the new carriage mount, I didn't think anything off it and simply abandoned that part and continued the other ones.

Today, I saw that the heating block is completely gooped up with PLA (see pictures). So now, I got two questions:

  1. How should I remove that gunk? I was thinking o| carefully peeling of everything without the silicone sleeve while the hotend is at a low PLA-bending temp, like 150°C, or 175°C.
  2. What caused this? Flowrate too high (the prints look the part)? Too fast extrusion? Heatcreep?

Thanks in advance. (:

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[–] Fenderfreek@lemmy.world 7 points 12 hours ago (2 children)

You have an incorrectly torqued connection between the heatbreak tube, nozzle, and heater block that is allowing filament to work its way past the threads and out the top/bottom. You’ll likely need to clean off what you can while hot in order to get it to a place where it can be disassembled and fully cleaned.

You may need to heat or even torch some of those parts clean, since there’s no generally available solvent for PLA to soak it off.

To prevent this, make sure you’re properly torquing those parts together according to the manufacturer’s instructions. Final torque is normally applied with the hotend empty and at temp.

[–] Prunebutt@slrpnk.net 2 points 11 hours ago (1 children)

Harumpf 🙄😤. It came like that. I only attached the extruder to the printer. I didn't expect that I need to open it up.

Maybe I should have fastened the nozzle, though.

[–] gafu@techhub.social 3 points 10 hours ago (1 children)

@Prunebutt @Fenderfreek

Its not about torque only.

If build up correct, the nozzle flange does not touch the aluminium heater block. There must be a gap, can be a tiny gap.

You dont want to screw the nozzle against the block, but you want to screw the nozzle backside face (around the filament bore) against the heatbreak end face. This is the place where you close the oozing hole, the threads are not tight against liquid plastic.

[–] Prunebutt@slrpnk.net 1 points 9 hours ago (2 children)

So that means I need to teardown the extruder and check the seal of the heatbreak?

[–] Fenderfreek@lemmy.world 4 points 7 hours ago* (last edited 7 hours ago) (1 children)

Sort of. As the previous poster pointed out, you need to make sure it’s assembled in a way that the nozzle is seated against the heat break inside the heater block, not against the heater block itself. You’ll have to do a complete disassembly to clean it up properly, and you may need to run a tap through the heater block to clean the threads, but when you assemble it, make sure that you back the nozzle off a turn or so, assemble the hot end so that the heatbreak is bottomed out against the nozzle, then heat it all up and torque the nozzle up snugly to the heatbreak(quarter turn past touching is usually sufficient). There are YouTube vids that will demonstrate hotend assembly better than I can explain it, but solid nozzle to heatbreak seal is critical for preventing this

[–] Prunebutt@slrpnk.net 1 points 2 hours ago

and you may need to run a tap through the heater block to clean the threads

I've cleaned the outside, but I don't know what you mead by that. Could you explain how I fix the threading?

[–] gafu@techhub.social 0 points 5 hours ago (1 children)

@Prunebutt

There is no seal like an o-ring.
It is bare metal to metal surface contact.

If there is a gap between nozzle backside end and heatbreak because the outer hexagonal part of the nozzle hit the heater block first (before the nozzle get tight at the heatbreak), it will leak through the treads and ooze out on the top.

If you can rotate the heaterblock after heating up the nozzle, then there is proof of the inside gap.

On a new hotend i disassemble it before mount it into the printer, screw in the nozzle in first and then turn it back half a turn.
Then screw the heatbreak in until it reaches the nozzle. Install it to the printer, heat to max used temperature, and tighten the nozzle again.

The heater block has bigger thermal expansion, so it tends to get loose by heating up.

If done correct you will never have problems like this, if the mating surfaces are even and not damaged.

[–] Prunebutt@slrpnk.net 1 points 2 hours ago (1 children)

It is bare metal to metal surface contact.

That's what I meant with "seal". 😅

Thanks for the advice. Gonna implement it.

[–] unexposedhazard@discuss.tchncs.de 1 points 11 hours ago

Yeah something is mega fucked. Never seen it like this.

[–] MaryPot@masto.ai 2 points 11 hours ago (2 children)

@Prunebutt

If it is only external, heat to 230-240 C and use a brass brush to clean it off.

If it has also clogged inside, heat to 230-240 C and run PETG through to push it out. PETG has a higher melting point than PLA.

If even that doesn't work, hubby said something about doing a hard pull, but not sure exactly how he does that, so I'll leave it up to others to explain.

[–] aarch64@lemm.ee 2 points 9 hours ago

AKA "cold pull"

[–] Marafon@sh.itjust.works 1 points 10 hours ago (1 children)

Hard pull or Atomic pull means to allow the pla inside the hotend to either cool to or heat up to ~80-100°C and then pull it out through the top. The semi melted plastic grabs clogs on its way out. Very easy and effective remedial action for small internal clogs.

[–] Honytawk@feddit.nl 2 points 8 hours ago (1 children)

Honestly, I do it every time I switch filaments.

It doesn't cost much time and you get a nice clean nozzle for a perfect print.

[–] Marafon@sh.itjust.works 1 points 6 hours ago

Same, actually.

[–] n3cr0@lemmy.world 3 points 12 hours ago

Heat it up and take it apart while the PLA is soft. Then have fun cleaning. You may have to use a knife.