Printer damaging failure

So yesterday I started a large print, that printed fine for about four hours while I was still at work, and then went home. This morning I came in to this.
Obviously the bed is not supposed to do that. After examining the print and the bed my best guess is that the z axis failed and started slipping down, and that the extra pressure is what eventually made the bed pop out of place. Then once the bed was out of place the print head kept on trying to print, but it was pressed into the bed and that damaged the bed. Eventually the bed got moved around so much that it unplugged from the printer and this is what stopped the whole mess from continuing.

See the other attached pictures.

Does anybody have any ideas as to what could have caused this specifically? I’m pretty sure I need to buy a new bed, since the one side is pretty torn up. Should I buy a new print head as well? Will a warranty or something cover this?

The nozzle definitly hit the part and knocled the bed off. Usually the belt would have slipped before enough force was applied to actually knock the bed off the mounts though. You can see what looks to me like the impact zone on the front edge of that part, though it looks like it hit with much more than the tip of the nozzle. It looks to me almost like the Z axis reversed (which I have heard of once before due to overheating due to fan failure or improperly vented enclosures on a Taz 3 and never since) and started driving downwards into the part. Then it hit one or more times and eventually knocked the entire assembly off. The position the Z axis is sitting at in the picture is lower than I would expect to see at that stage of the print. It’s also possible you lost a bed washer under where the bed is sitting, the bed flopped up and hit that way

The damage doesn’t look catestrophic. You can apply a new PEI sheet sourced from Lulzbot or IT works. The bed wire harness and the nozzle heat brake tube would be my biggest worries. You may also be looking at replacing the rods if you bent any of them. Possibly the bed mount plate too if the corner bolts stripped out on any of the corners.

As to what caused it, the biggest factor is printing unattended. Please be aware that without the thermal runaway protection firmware on the Taz 6, you probably would have burned down your office. You should never leave a major heat source like that unattended. Period.

All the Taz 6’s are new enough they should be under warrany, but you would need to check with Lulzbot to see if they will cover you in this case. It’s possible this was due to a control box fan issue or something along those lines, but its also possible thatit was caused by a printer in a small room operating in a building where the air conditioning is shut off at night and the thing overheated due to user error. They may want it back if nothing else just to investigate the failure and see what actually went wrong.

So after looking at it some more I am a bit confused about what happened. The print looks like the head started to slip in the Z and was pressing hard down into the print, and the bed is damaged from the head pressing into it after the bed had poped out of place. Also when I first got back to the printer it was bottomed out in the Z and I tried to use the printer controls to move it up, and it would not move. This is what led me to believe that the Z axis was broken in some way.


After restarting the printer I was able to move the Z axis and it auto homed with no issues, and the Z axis seems to be working fine.
I do not know what could have caused the printer to do this if the Z axis hardware is all working fine.

Thanks for your thoughts!
Since the Z axis is working now I am also thinking that the printer somehow reversed the Z axis direction mid print. The reading on the screen said like 19mm Z height but it was actually in a Z 0 or negative position somehow.

I checked and all four washers in the corners that hold the print bed down are there and they look fine.

I have never heard of any safety issues with running a printer overnight. We have had this printer for a while and have run many long prints overnight with no issues. I looked it up and running overnight seems to be common practice. I do not have some DIY heat chamber or anything that would be a fire hazard.

I wonder if there is some diagnostic that I can run on the motherboard that would tell me if there was a fan out or something like that.

It’s always a risk leaving something that works with high heat around flammable material. How risky it is can be debated, but there is always some. Ideally, the machines would have more safeguards like watching the Z position, even roughly. It doesn’t need sub-mm precision, but even 1cm resolution would prevent this sort of thing. That adds complexity and cost though, so I get why it’s not commonly done. Thermal runaway protection in the firmware is a good start.

I leave jobs running often, I do check in on them with a Pi camera, but I do try to be nearby just in case. I suppose you could put the printer in a fireproof bunker, but I doubt most people will.

There are situations where it is possible for a 3d printer to fail in the on position, and continue to increase voltage to the heater core until it reaches temperature sufficient to melt the aluminum heater core block. Once that melts, the molten aluminum falls on the 3d print, ignites it, and then Bad Things occur. THe Taz 6 has thermal runaway protection enabled so those conditions are much less likely to occur, but it may still be theoretically possible. If that had been a Taz 5, that would have ended badly because you triggered the thermal protection subroutine in the picture. The 5 didn’t have that.

Time lapse -
Same event real time

Unless you have the Taz inside a fire rated enclosure with a suppression system, I would reccommend against running it unattended for long periods of time.

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You know, I love my printer and I think they are about as good as they can get with current technology VS. price point but I never leave the house with it running. It’s still a machine with high temperatures moving parts and flammable materials and that just screams supervision to me.

Seriously you should be careful with any 3D printer. Over on the RepRap board they started a safety section after one post about a guy almost burning his house down (luckily he was in the other room and smelled smoke) as his hotend controller failed and super heated the nozzle to the point that it caught the plastic parts around it on fire then his curtains behind the machine and so on. <---- Safety forum