A tale of wrecked hot ends and damaged cables

[Alex-Stone]

I left a long print on overnight last night. Came down this morning to discover that the entire print had stuck to the nozzle in a large molten mess. It had pushed the magnetic print bed off the heated bed entirely and was still attempting to print directly on to the heated bed, but just gunking the tool head up more.

I wasn’t quite sure what had happened, but something had clearly gone very wrong.

I had to cut the filament from the toolhead; the nozzle would no longer heat up to unload. To replace the hot end kit with the spare, I had to completely disassemble the toolhead. It had glued itself in - dried filament completely encased the hot end - including on the inside of the toolhead and the hot end wires. What a pain. The plastic hot end surround had also begun to warp.

Finally, with that back together, I attempted a small test print to see that everything was working. The toolhead and nozzle work fine - it reached temperature and I could load the filament which flowed freely. The hotbed however did not want to warm up.

Upon further inspection, I discover the root of not only this problem, but likely the cause of the failed print which destroyed the hot end. The heated bed cable had a split. Holding it at a different angle, I could hear it spark and the bed would begin to heat up - and let go, and it would stop.

The cause of this split is that the cable was angled downwards and, when the bed travels back and forth, it catches on the splitter boxes underneath the bed, repeatedly bending it to the point of failure.

Taking the heated bed off, it’s clear that one of the wires inside the cable was completely severed. The sheath was also burned through. That would explain the electrical smell…

I cut the cable free from the heated bed, just below the break. I then resoldered it back onto the bed and now everything works again as it should.

Word of warning to other users - make sure the cable is routed pointing upwards from the heated bed!

I’m just glad I could replace the hot end and fix the cable without much additional damage. Could have been worse; nothing caught fire in the night. A replacement hot end from Snapmaker wouldn’t go amiss though…

As a new user I’m restricted to only one picture per post, so I’ll post them individually below.

[Alex-Stone]

[Alex-Stone]

[Alex-Stone]

[Alex-Stone]

[Alex-Stone]

[Alex-Stone]

[stewl]

There have been a number of threads about this in the forum.
The one has some ideas about cable relief. I printed the spiral one in PLA. Way too hard, couldn’t get it on the cable, Then printed it in TPU, doesn’t contain enough cable clamping and can still catch on the splitter boxes. I ended up using the existing cable clamp making sure it clamps the cable sheath plus half the TPU spiral for strain relief. I also printed a cable clip like the one used for the head cable to lift the bed cable away from the splitter boxes.
It’s definitely an area that urgently needs improvement.

Snapmaker 2 heated bed cable hazard

I have a Snapmaker A350 and have been using it for 3D printing for several months. I recently noticed that the cable that attaches to the heated bed was bending and twisting during the printing process in a way that was inducing wear and tear on the cable. A small lesion had developed already at the junction where the cable meets the heated bed. I wrapped the area with electrical tape to reduce the bending. A few weeks later, the printer stopped working and I noticed the cable had burned through…

[Alex-Stone]

Thanks - It’s both reassuring and also slightly worrying to know that I’m not the only one to have had this issue. I’ll email Snapmaker Support and see what they say.

[avacado]

I read somewhere, not sure where, that twisting the cable twice before plugging the controller in will keep the off the splitters. I did this and it does indeed keep the cable from binding on the splitters. It may not adequately service the purpose of strain relief but it does work until you can print an adequate strain relief device of find something else.

[Edwin]

@Alex-Stone

Upon further inspection, I discover the root of not on

Hi Alex, I have received your email and will take care of this issue. Sorry for the inconvenience.

[stewl]

Hi Edwin
A recommandation from Snapmaker to reduce the chance of this happening would be welcome. We are all trying to work out our own way to avoid the issue.

[CarlosPereiraPT]

Hello,

Had exactly the same problems, both the mess on the print head, that took me hours to get rid of it, and the broken cable that heats the bed…

Just to mark as one more user with both problems.

Regards,

OdinPT

[JR17]

I had a similar problem (though mine was the screw holding it loosening and dropping it into my print). I note that the wires came out of you print head as well. The problem with the print head wires coming loose occurred on both the extra print head and the one that fell out of the hot end.

Anyone else having this problem? Can the two wires shown just be soldered back into the hole or are they suppose to attach to something inside?

[stefix]

Put it back into the hole and secure it with some nonconductive thermalpaste.

[Alex-Stone]

Looking at the spare, I don’t think the wire (with the red/clear tip) is meant to be fixed into the hole - it hangs free. I just inserted it into the hole before fitting the hot end and all seems to be well.

[stefix]

@Alex-Stone Thats a way too, it was only a hint.

[Edwin]

As you can see in the pictures below, the thermistor is shorter than the heating tube wires and you can put it in the hole when it is bent.

[edf]

@Alex-Stone

The plastic hot end surround had also begun to warp.

I had a similar situation yesterday and spent last night tearing apart the print module so I could get the PLA (and the old hot-end) out. There is warping of the fan vent, and to a lesser extent of the plastic part across the nozzle from the fan (sensor mount?). That second part seems to move around a bit and I’m not sure whether this will impact the printing. I admit to being a bit surprised that meltable material was used so close to the nozzle.

Did you have any issues related to the warped parts once you reassembled the print head?

[Alex-Stone]

I think the sensor is designed to adjust vertically as it’s screwed into the slot on the back. I marked where it was prior to disassembly so I could return it to the same position. Not sure how they’re factory calibrated or what effect it’ll have on the print - I think it’s do with calibrating the bed level, so if the sensor is off, the machine might think the bed is at a different depth to where it is.

I actually used a heat gun to soften the warped vent so I could mold it back into shape and ensure airflow was open. I haven’t had any issues since reassembling, however Edwin (staff support) was very helpful and sent out a replacement head along with a replacement bed. Shoot him an email and I’m sure he’ll be able to help you out too.