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printer stops midprint with bed and nozzle getting cold

lillyand31cdac2b
(@lillyand31cdac2b)
Significant Member

my printer has begun to stop mid-print with the nozzle still on the print. When I´m detecting it, the nozzle and bed are always cold, the screen shows normal printing temperature for both, nozzle and bed, but is frozen. Nothing works other than switching it off.

sometimes it´s after hours of printing, sometimes in the first 30 seconds of a print. When I´m pre-heating nozzle and bed, both heat with no failure and if I´m starting a print it will work for some time and freeze again. the only way around it is to let it print with a cold bed. even if I set the bed temperature way below room temperature, it won't print until the end. Only with a bed temperature of 0 it prints without failure...just the prints don´t stick so well to the plate

I can´t find any broken wiring and I don´t know where to look for the problem, what should I replace?

It´s an Anycubic Mega S, no fancy remodelling, strait out of the box like my other one, which is printing like a workhorse

 

Quote
Topic starter Posted : 21/09/2021 5:39 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Lilly,

Welcome to the community!

Are you using the SD card that came with the printer? Those are notorious for being low-quality and very prone to being corrupted. Of course once a printer encounters a corrupted file it won't know what to do; its processor will crash and the axes will stop dead in its tracks; a power cycle is the only way to reboot the printer and start the processor working again.

Try a simple short print (like a calibration cube) using a good-quality name brand SD card and report back. If the printer crashes, try printing the same cube again and report back whether it crashes in a different location the second time. That will help narrow down the possible hardware sources.

---

Other than that, are the bed temperature readings sensible (eg. do you get a reading of 60°C if you set 60)? Do they fluctuate a lot if you just set a temperature and leave it without actually printing anything? Can you use an external thermometer (like an infrared temperature gun) to check the bed temperature?

Looking forward to your feedback 🙂

 

Regards,
Luke

ReplyQuote
Posted : 22/09/2021 9:16 pm
lillyand31cdac2b
(@lillyand31cdac2b)
Significant Member

Hi Luke,

Thx for the replay. I did change the SD-card months ago and got a 16GB from SanDisk. I use those on both printers and they seem to work well on the other on.

I tried printing several different small things, none of them worked. With non of the cards. The printer stops sometimes after a couple of minutes, the last t times it did stop while printing the skirt but not always at the same point. Sometimes it gets a full round of skirts before stopping, the last print did stop after 2 or 3 cm of moving.

The tech support of anycubic thinks it is the heatbed, because the cold bed printing always works. I'm not so sure with that. Why would it freeze the printer? Shouldn't I be able to stop the print even if the bed is getting cold? 

I will try the external thermometer tomorrow and give feedback

ReplyQuote
Topic starter Posted : 22/09/2021 9:36 pm
Luke
 Luke
(@lmf5000)
Expert Moderator

Hi Lilly,

That's odd. If you have a multimeter could you also test the resistance of the bed thermistor? While you're there, check that all the wiring to the bed is secure (both the wires supplying the heater and the ones for the thermistor).

One possibility is that your power supply is bad. Since the heated bed is by far the largest consumer on the whole printer (it draws about 200W alone. The hotend heater is about 30W and all the processors and motors collectively are only 20W), when the bed is on it puts significant load on the power supply. Your faulty supply might be dipping below the proper supply voltage (which would be measurable on a multimeter), or worse, could be that the power supply generates a noisy output at high load that causes the processor to error out (this is harder to check - would probably require an oscilloscope - easier to swap out power supplies and check if the problem is resolved).

It could be that the bed is bad - perhaps some of the traces have shorted and it's drawing more than it should from the power supply. In that case it would overload the supply and cause some of the effects mentioned above. However if it's a heated bed issue, then in theory you should be able to replicate it without printing at all. Just set bed temperature to 70°C, walk away and check back every 5 minutes to see if the printer has crashed. If it survives for 30 minutes with no issues then it points to the issue being software-related. Possibly a fault on the mainboard.

If you could upload a video of the printer when it freezes that would help somewhat in troubleshooting. Also, could you attach a sliced gcode file that caused a crash so I can inspect it?

Looking forwards for your feedback 🙂

 

Regards,
Luke

ReplyQuote
Posted : 22/09/2021 10:13 pm
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