[Cerrado] MK3 resets while printing  

Re: MK3 resets while printing

This has been happening to me as well. I have octoprint hooked up through usb and octoprint world report the printer reset for some reason. I also have seen it happen. I have been pulling my hair wondering why this is happening. I did notice that one time i had static built up while walking through the room and discharged on the printer which caused a reset. I started to wonder if the frame was grounded good enough through the power supply. I did hook up a ground directly to the frame and so far it hasn't happened again. Not sure what else to try.

Re: MK3 resets while printing

😮 Yes, USB could be the reason!! I had made the firmware update before I started the print and I remember, that I left the usb cable in the printer while it was printing from SD card. Maybe the PC went in stand-by and gave some impulse over the USB cable..... 😉 I can't really tell, because I was working on my Mac and the monitor of my PC was off.
I think it is always good to remove the USB, if it's not needed.

timothy, thanks for your starting hint

Re: MK3 resets while printing

May be power issue (under-voltage) that causes to MCU to restart.

Re: MK3 resets while printing

Well I have some more information to provide concerning the unexplained resets I have been having. It turns out that the office where my printer is located has a small bathroom with a single fan in the room and it just so happens that this fan is on the same circuit as the outlets that feed the printer. When the fan is on no problem but when the fan gets switch off the printer resets. The house is a new house and the wiring is up to some pretty new standards so I started to look at why this might happen. The only thing I can come up with is that some how this fan is generating some back EMF on the circuit and the power supply in the Prusa cannot filter it out. Last week I had my power supply fail in a very common recurring way discussed in this thread https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/power-supply-failure-t13443.html and it was replaced by Prusa. I know that I had these issues on the old power supply but never realized what is causing it. After following the PSU failure thread it seems to show that that the Prusa PSU fails almost exclusively in the US on 120V ac. I have to wonder if the PSU was tested primarily to standards meeting a European 220V standard and never was fully tested on the 120V ac. If this is the case then most power supplies have some sort of a circuit containing a MOV (Metal Oxide Varistor) that will shunt these types of voltages. If the MOV is not rated specifically for 120V then it won't work. I never opened up the PSU to confirm anything but am mostly just wondering and theorizing. Anyway I have always had all the equipment in the office on standard surge suppressors and also have on order a APC UPS to maybe clean up this circuit. Either way in the long run it may not have been the best idea for an Electrician to put a fan on a computer circuit but how was he to know and I don't think it violated any code. I am going to try and move the fan off of this AC circuit as well to hopefully keep it as clean as possible.

Re: MK3 resets while printing

We are having the same problem. Can't even print small files. MK3 stops printing in a random location, resets after a minute, has no fail stats.

MK3 kit build was completed 4 days ago (not by me, but by the competent mechanic of the family). We ran the calibration wizard, then successfully completed four prints:

1. Prusa logo #1 - from Prusa supplied SD card
2. Prusa logo #2 - from Prusa supplied SD card
3. Tree frog #1 - from Prusa supplied SD card
4. Duplex_2Gang_Standard from Thingiverse, sliced w/ Prusa3D Slic3r MK3

Photo of prints 1-3 above...

Next we tried printing the bottle opener from the Prusa SD card, and the trouble started. After many tries, research, and troubleshooting, this is what consistently happens:

(1) Some random portion of the file is printed
(2) Printer stops and LCD freezes in printing mode, showing the partial file name and frozen % complete
(3) Pushing or turning LCD knob has no effect
(4) After a little over a minute, printer resets on its own...
(5) LCD briefly displays the Sorting Files screen
(6) LCD briefly displays Prusa Original i3 startup screen
(7) LCD displays the ready screen
(8) There are no current or past fail stats - all zeroes.
(9) Nozzle remains in position where printing stopped until Z-axis raised manually.

Photos of (2), (6), (7), (9), printing tree frog #2 (click for full size)...
http://www49.zippyshare.com/thumb/ne77A2qk/file.html http://www49.zippyshare.com/thumb/PVO7OrWx/file.html

Listing below the prints we've tried since the problem started, and troubleshooting done so far. All were printed from Prusa supplied SD card unless noted otherwise. All prints listed below stopped randomly as described above, with no intermittent successful prints. All small files.

Reset 1) Bottle opener #1
Reset 2) Bottle opener #2
Reset 3) Bottle opener #3
**Troubleshoot: copy files from SD card, format SD card (no sector errors), copy files back to SD card. recalibrate printer (full).**
Reset 4) Bottle opener #4
**Troubleshoot: correct build error where braided cable cover was not found in shipment (till later) and spiral plastic wrap used for heatbed cable cover per older instructions. swap cable covers and check thermister connection (good). recalibrate.**
Reset 5) Bottle opener #5
**Troubleshoot: clean a thin film of melted filament off the bottom half of the nozzle. try printing tree frog which previously succeeded**
Reset 6) Tree frog #2
**Troubleshoot: print from pronterface on windows laptop via usb**
Reset 7) Tree frog #3
Result: Pronterface stopped reporting when print stopped, then reported a printer reset after about a minute (same as LCD w/SD card)
**Troubleshoot: update firmware to prusa3d_fw_3_1_3_mk3.zip (march 8). when removing steel plate for calibration, LCD went nuts (static?), displayed hieroglyphics. power off printer switch and power back on, LCD seems ok. recalibrate. set printer speed at 76%. plug printer into operational surge suppressor. unplug usb cable and switch back to SD card.**
Reset 8) Tree frog #4
**Troubleshoot: next, printer grounding...**

Photos of Reset 1-5), Reset 6)...

Re: MK3 resets while printing

MK3 is finally printing again! Resident hardware guy studied the internal grounding of the MK3 and found a what looks like a problem, with an easy fix. He tried it, then successfully completed a print.

Photos of successful print and fix...

Fix:
Ground the Einsy board to the metal printer chassis. Can be done at home like this: Replace one of the screws holding Einsy to plastic with a longer screw which pokes out of the plastic enclosure. Place another screw in the metal printer frame and run a jumper wire between them. About 3 cents for us to fix at home. Probably about a half cent for Prusa to add an angled metal strap to connect Einsy to metal frame via existing short screws.

Explanation (paraphrased):
In the current MK3 design, the Einsy board does not have a chassis ground. Einsy is screwed to a plastic box and the plastic is separately screwed to the metal printer frame. The only electrical path available to the Einsy is the power supply/return. This lack of chassis grounding could cause the following issues, which in turn could cause the printer to stop:

Will update after further experience.

Re: MK3 resets while printing

68 hours of successful printing since the chassis ground was added... we're calling it fixed.

Re: MK3 resets while printing

Nice cath, the board is not connected to the PSU EARTH, but PSU chassi is touching the printer frame, so frame is connected to earth as the psu have a earth point and by design is always connected to chassis.
I agree that board should have a earth terminal and make use of it, but a direct connection of GND to EARTH can also lead to some problems, depending from house to house and board design, but more important is that fix your problem 🙂

If you want to get rid of that ugly cable floating arround, you can tie it to the PSU EARTH directly and run cable under the printer near the + and - PSU cables

Re: MK3 resets while printing

Yes, it's a very complicated topic from what I understand (which is not much), and there are many opinions on the "right" way, and the correct answer can vary depending on (...)

Here is a reference which more or less aligns with resident hardware guy's general idea (my understanding being very limited); see the accepted answer: https://electronics.stackexchange.com/questions/19561/should-chassis-ground-be-attached-to-digital-ground . It's not the exact same situation, but it's close to his thinking. Resident hardware guy is enjoying printing now, and is tired of talking about this. 🙄

Re: MK3 resets while printing

I can't believe i did not think of this being the cause but yes it was the problem. The point i implemented the ground strap the resets are gone from the fan on the circuit etc. No problems anymore. Thank you for finding this.. Hopefully Prusa will look at this and implement this into the build.

Re: MK3 resets while printing

Happy that you don't need to rewire your bathroom fan to make your 3d printer work.

Re: MK3 resets while printing

It looks like someone else reported this same problem and successfully applied this fix...
https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/random-resets-earthing-problem-easy-fix--t14986.html

Re: MK3 resets while printing

I spent some time looking at this while planning to pro-actively replace the stock power supply with a meanwell HEP-320.
That power supply can't easily be mounted to the frame, so I plan to use it like a gigantic laptop power supply sitting on the table next to the printer.
That got me into looking at the grounding more carefully.

Normally (MK2 and MK3), the power supply housing is bolted to the main printer frame. The power supply housing is earth grounded via the IEC cord.
On both the MK2 and MK3, the control board is floating from earth ground. It's only 12 or 24V, so no big deal from a safety perspective,though debate-ably not great from a noise perspective.

One interesting observation, however, is that the frame isn't actually that conductive.
If I measure my MK2 from the case of the power supply to the screw that holds it down, of course it's near zero.
However, if I measure from the frame of the power supply to the screw that holds the board enclosure on, it's > 20 meg!

Edit: The frame is supposedly made out of "dural" which is an old trademark for an Al/Cu/Mn alloy. Should be conductive.
It's possible (but would be surprising) that the powder coating on the threads is thin enough not to bind the screws, but thick enough to insulate the bulk of the frame from the screws in some cases (mine at least).

That leaves two questions in my mind.
1) Why do the MK3s seem to have an issue but the MK2s do not. Yes, the boards are different, but not that different.
2) If the screws don't electrically connect to the frame, then the extra ground strap shouldn't matter. Maybe my frames are different than average?

In my case, I will run a discrete ground wire from the case of the HEP to the board and skip the frame connection. I'll report any issues if they come up.

Re: MK3 resets while printing

If one is printing through Octoprint or your computer, I assume that the ground from the UB to either of these should be sufficient?

Prusa care to comment?

(I had a print randomly reset 7 hrs into a 12 hr print and am trying to diagnose).

Re: MK3 resets while printing

Well, a son that stays up late playing video games has some advantages. He told me that the lights flickered in the room (possibly the whole house) at 1:47 am. Computers didn’t reboot, but obviously the Prusa didn’t like it.

Now to find a cheap UPS.