Check your hot end heater isn't lose!

I had never though to double check the hot end heater, and had it drop out mid print last night. The thermistor no longer got heated so of course it just sat there on full power in the middle of the printed plastic. Confounding the problem was that Repetier Host then crashed, so the gcode to turn the heater off never got called. It sat there for quite a few hours glowing in the plastic.

The result?



I was very lucky not to have a major fire. I'm printing PLA so there's just a smell of burning sugar in the house now, but I'm pretty sure ABS would have burst into flame. I also have the max power dialed down to half in the firmware which probably helped as well. Damage seems limited to the glass printing plate, and the heater element.

So, lesson definitely learned. Check the hot bits before you print!

And I've just seen that Marlin has added a Thermal Runaway protection feature 9 days ago! A firmware update and reading of the config file would have saved things here.

Great work by the Marlin developers, definitely a fantastic and important feature. The heating element and the thermistor parting ways is a definite recipe for a serious distaster.

Tks for sharing.

Can you post a pic of the hot end, I'm curious of the bolt location, and orientation that retains the heater cartridge, and what hot end is it? How much time has it been since the bolt was last tighten? Is the wiring inflexible, and did that pull the heater cartridge out?

That looks to be an E3D v5 based on the fan shroud and what I can see of the heatsink. If it is the set screw is located on either the top or the bottom of the heater block depending on which way you assemble it.

Yep, it's an E3D hot end (V5). There's a small grub screw at the bottom of the heat block that tightens onto the heating element. Having examined everything a bit more closely I'm mystified as to the reason for the failure. The grub screw hadn't moved (i.e it took some torque to get it loosened) and the replacement heating element I'm just fitting didn't fit into the hole until I had loosened it. I guess the element deformed over time and changed shape enough to just slip loose. I hadn't checked the screw for ages, but if I had I think it would have felt tight. Of course the element would probably feel loose, so that would have been a giveaway

To not panic other E3D owners, this wasn't the original heater that came with the hot end, I'd replaced it after I cooked the original one (through my own foolishness as I learned all about hot ends and thermistors!) This one came with a cheapo j-head clone (warning lights go on for anyone?) but had been working fine right up till this point.

I'm putting it all back together and wrapping some extra layers of kapton around the whole thing just to make sure. Still can't believe how lucky I was that the consequences weren't much worse...

Quote
Opus
The grub screw hadn't moved (i.e it took some torque to get it loosened) and the replacement heating element I'm just fitting didn't fit into the hole until I had loosened it. I guess the element deformed over time and changed shape enough to just slip loose.

My E3D had a similar problem, but I caught it before the heater popped out. I suspect that the cartridge expands faster than the heating block when warming up, which causes the outside casing on the heater to dent and deform under the grub screw. Mine was definitely not round when I took it out, and I put it back in with both the grub screw and a loop of kapton tape around the block as a security measure.

It does bear mentioning that my E3D came from MTW. I suspect that they are buying only the metal parts from E3D and substituting their own heaters and thermistors, as the thermistor comes pre-assembled (no complaint!) whereas the E3D assembly instructions spend several steps crimping the thermistor leads. I don't know if the heater is also the same deal.....

I've got the v5, screw and heater are tight as always. Original direct from E3D-Online. The way I have my kapton tape and baked thermal compound, it's not going anywhere, screw or no screw. Thanks for the reminder to check though.

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Realizer- One who realizes dreams by making them a reality either by possibility or by completion. Also creating or renewing hopes of dreams.
"keep in mind, even the best printer can not print with the best filament if the user is the problem." -Ohmarinus

Opus, I feel for you.

I filled the living room with smoke in the early days when my thermocouple got pulled out.
swmbo came running out to me in the garage saying the house is on fire.

Klapton tape is not that good for keeping the thermocouple in place. E-Z Fuse Tape is the best I have found for the application.

Thanks for sharing your pain.
We'll pay more attention if we are running ti over night.

Safety first!

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BotFeeder - Professional Manufactured 3D Filament

Thanks for the posting, I will make sure to further tighten the screw after it heats up (just pladed an order from filastruder for a v6, discount code "reprap") This probably wouldnt happen with my anubis clone, as I drilled a hole deep into the block for my thermistor, and the heater wires are cable tied to the extruder mount So it cant slide out.