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Creality CR10-S printer is failing with "thermal runaway" #1163

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ajlennon opened this issue Jun 30, 2019 · 8 comments

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@ajlennon
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commented Jun 30, 2019

The bed is heating and it seems to be reading a temperature increase.

But after a while the system halts with a "thermal runwaway" error message.

Also the heating bed connector at the rear of the main PSU box is getting very hot.

Others have apparently seen this problem

https://www.reddit.com/r/CR10/comments/8a6s05/is_it_normal_for_the_bed_cable_connector_to_get/

I've contacted the vendor for a response

@ajlennon ajlennon self-assigned this Jun 30, 2019

@Thingomy

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commented Jun 30, 2019

Hot bed connector was found to be underrated (either 5A or 1A) when it was taking 10A. It turns out the connector was getting hot enough to melt it's solder, and was being held together by heatshrink. Connector has been replaced with bullet connectors.

Box was reassembled and machine was fired up, whereupon a clunk was heard from inside the box, this turned out to be the hotbed mosfet falling off due to overheating melting it's solder. It was soldered back on on the offchance it was a one off; it wasn't a one off. I'm 95% sure there is no short in the hotbed.

Machine is currently in pieces awaiting either somone that knows thier way around mosfets to prod it, or me to bring in a bunch of additional tools.

@zarino

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commented Jul 1, 2019

When I hear the word "mosfet" I immediately think @magman2112 – pinging him here in case he has any expertise to lend!

@ajlennon

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commented Jul 1, 2019

Hehe. Yes @magman2112 was involved with @Thingomy in the investigation.

I've had a response from Ristar, whom I bought the printer from via Amazon

Dear Customer,

Thanks for your contact.
We apologize for the case you meet.

Could you please provide us more specific information about the problem?
you can also take some photos or a short to show it, then our technical will specify the problem.
And we will according to the reasons do the appropriate treatment. We appreciate your cooperation.

Looking forward to your reply.

Kind regards

My response:

Hi,

Thanks for your response. We've done some more investigation here and it appears as though you are >putting more current through the heating bed connector than its specification allows.

Notes:

"Hot bed connector was found to be underrated (either 5A or 1A) when it was taking 10A. It turns out >the connector was getting hot enough to melt it's solder, and was being held together by heatshrink. ... >Machine was fired up, whereupon a clunk was heard from inside the box, this turned out to be the >hotbed mosfet falling off due to overheating melting it's solder. It was soldered back on on the >offchance it was a one off; it wasn't a one off. I'm 95% sure there is no short in the hotbed."

I am not in the office today to provide pictures but the issue appears the same as on this page. So it >looks like others are seeing this problem too.

https://www.reddit.com/r/CR10/comments/8a6s05/is_it_normal_for_the_bed_cable_connector_to_get/

I like this printer a lot and have been recommending it to colleagues in my workspace, but I am >concerned about the issues above. Please help to resolve them so I can continue to recommend you >guys!

Thanks,

Alex Lennon

image

Will keep this issue updated with their response

@DocTrucker

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commented Jul 2, 2019

I'd mentioned about the hazards the Anet printers on the DoES Liverpool google mailing lists last december and the Creality machines and most at the same price break are very similar. Even the much more expensive Up Printer has very small CSA wire for the heaters.

The creality machines at least used to ship with a version of Marlin with thermal protections disabled, thankfully that has either changed or you caught it.

It's note worthy that the Ultimakers are one of the only suppliers to say their machine can run unattended on the CE certification.

All that said I'm working on the safeties on my 'small holding' at home to save any potential grumbles from the insurance company. Passive saftey (ie heaters at 100% duty never reach a dangerous temperature) is first, but is generally frustrating. Firmware safteys are the next option, and finally thermal fuses switches and fuses mounted on the hot zones can save your building if it all goes belly up.

As with most electronics it's the negative leg that is modulated for heater control so you can feed the posative side of the heaters seperately to the rest of the board (tied negative poles) and interlock that PSU on faults. Most boards have a PS_ON pin which can be used to drop relays. If you go down that route remember SSRs and MOSFETs are not safety devices.

@jrp

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commented Jul 3, 2019

I'm planning to be in tonight with the right tools to to do some more diagnostics on this.

@DocTrucker

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commented Jul 3, 2019

Expect I may be stating the obvious to you but have a good look over the pluggable heater contacts for signs of arking and check gauge of wire against the expected current draw. If the creality is the machine I'm thinking of it's got (or previous models had) an aluminium heatbed. It's worth ditching the connector and soldering wire (maybe new) directly to the bed and fully stress shield the joint. If you do this preheating the aluminium plate on a gas stove helped me. I needed a gas powered soldering iron to get enough heat to work with high temp (silicone insulated) 14awg, but that is potentially overkill for a standard heatbed. Check thermistors are secure too where they are removable.

@Thingomy

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commented Jul 3, 2019

I had a look tonight at the mosfet arrangment to switch the heated bed, it is an off the shelf board that effectively emulates a relay. It is officialy goosed. That tends to happen when parts get hot enough to melt off. I replaced the failed mosfet with a much lower rated one for the purpose of testing whether the board worked, and it still does nothing.

So we need a replacement for this board.

As for how it died, I'm puzzled. The Mosfet is actually well over rated, (98A is mentioned in the datasheet, which is about what I'd spec for driving a 10A load), and the connectors and wires in the area look up to spec too (other than the one that started all this). It's possible I did something to it during the other fix, but I can't work out what. I even confirmed I never reversed it's power supply, which would have had this effect.

I'm now unavailable for a few weeks, so I'm going to have to hand this one off to the next interested party.

PS. I left a bag of mosfets in the area, could someone either keep them with the machine, or stick them in my box please?

PPS. I got as far as to work out how the mosfet overheated so fast. It failed mostly conductive, at 0.18ohms (including some of the wiring) so as soon as the PSU came on, it imediately outputs a measured 7.8amps to the hotbed; and so runs at 13ish watts, and the heatsink fails to disapate it. It's possible that during it's failing process it's resistance was higher, producing more heat.

@DocTrucker

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commented Jul 4, 2019

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