My printers stopping randomly

Both of my printers (CR Ender 3) stopping prints randomly at the same time. Sometimes I had this issue when both printers were running, but it happenend to a single printers before when the other was turned off.
I had both printers connected to a dual channel shelly when I first discovered that behavior and thought the shelly might be the source of these issues. I wired both of the printers to seperate shelly 1, same troubles.
I dont think that is because of bad wifii connection, there is a wired accesspoint next to the printers.
Everytime I noticed that a print stopped, octoprint said there is no serial connection to the printer. Maybe the serial disconnected for some reason casuing the printer to stop and stay at its position.

One printer had showed a hint that there is a undervoltage issue, nothing that I worry about in this case, because both printers having thouse issue.

I dont think the shellys are the problem either, the logs doesnt list any powerlosses or switching commands.

Does anyone had something like this before and can tell me how to solve this problem?
Btw, the printers worked fine without octoprint, wich is why I think octoprint or the serial communication is wrong in some way, in the other hand, both printers have serveral rasperrys and shellys...

Hello @FloLikesCookies !

It's quite difficult to give an answer here.
The template you have deleted was there for a purpose: to give us helpful information to help you.

Besides that you are using Ender 3 printers, we know nothing about your setup.

Also, if you may have not seen something particular in the logs, maybe we do.

To be sure the shellies are not the problem, you should run your setup without them.

If you want to add the missing information that have been asked for in the template, please do it in a new post. We do not get any information when someone edits a post.


A single Creality printer has been known to generate enough EMI / RFI to cause communications problems. Put two of them together and...

You need to use quality, shielded USB cables with ferrite cores on both ends. You may have to reroute / shield the internal cables in the printer(s).

Without the additional information that has been asked for. We can only guess.

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As Ewald_Ikemann mentions, more info is definitely needed.

With that said, I can say I've seen similar behavior from my 2 ender 3's that are connected to a single rpi. From what I've seen, an EMI issue on one printer can take the entire root USB hub down momentarily, so every single USB device on the rpi will disappear and then come back.

The cause of that EMI could depend: backpowering, crimped LCD cable or even just one of the USB connections being a bit loose so when the printer starts to vibrate a bit it just jostles it enough to interrupt the connection momentarily.

It's also possible that it's not even one of the printers causing the issue, if you have something like a touchscreen or other peripheral on the RPi that's drawing power or potentially causing the same type of USB issues as above.


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