This could have ended with a house fire...  

RE: This could have ended with a house fire...

For some reason, the forum ate the text of my post, so here it goes:

I bought my printer few months ago and for the most part, it's been running perfectly well. I noticed that every so often it would reset without a clear reason.

Few days ago I decided to add an enclosure to my printer to improve my result with high temperature plastics. The first step was to remove the power supply from the frame and since then, the reboots got far worse, to the point that the printer would sometimes just cycle repeatedly.

That got me worried and I started to look for the issue -- and I sure am glad I did!

The screw in the problem terminal wasn't just loose, it was falling out! Only the plastic cover kept it in place. The remaining screws were bit loose too but nowhere near bad.

Prusa, please please improve your QC around the power supply -- it is not easy to get into and verify.

RE: This could have ended with a house fire...

Prusa does recommend checking PSU and heatbed cables as part of routine maintenance. See step 5.

RE: This could have ended with a house fire...

I don't think this falls under that purview. Yes, it should be checked, but it is not made easy in the old silver supply since it involves disassembling your entire printer to get enough slack to remove the printed cover. Step 5 also does not mention the connections *inside* the PSU. I don't think it's reasonable a user should have to do that, especially since this was factory-assembled and hopefully tightened to a torque specification. 

It's obviously much improved in the new black supply since the terminals are readily visible and accessible

RE: This could have ended with a house fire...

I'm also not sure how much "house fire" is  knee-jerk overreaction. The PSU has thermal protection, and will shut itself down (or blow a fuse); contrast that to other documented printer meltdowns where the heating element is isolated and the system can continue to pump power into it without knowing anything was wrong when the safeties are disabled.

PETG (of the cover) also has some flame-retardant properties, unlike ABS for fan shrouds, or PLA. 

RE: This could have ended with a house fire...

Posted by: bobstro

Prusa does recommend checking PSU and heatbed cables as part of routine maintenance. See step 5.

I don't think the PSU assembly is expected to be disassembled by a user. That wouldn't meet certification criteria as there are live wires exposed under the PSU assembly plastic parts (the power panic PCB).

RE: This could have ended with a house fire...

Posted by: Vojtěch

I don't think the PSU assembly is expected to be disassembled by a user. That wouldn't meet certification criteria as there are live wires exposed under the PSU assembly plastic parts (the power panic PCB).

Just saying that regular checks might reveal such a problem before it becomes serious no matter how it is ultimately resolved. OP had removed and repositioned the power supply, so extra checks are a good idea.

After spending some time lurking in the 3D printing Reddit groups, checking for potential house fire issues is a part of everyday life for those folks. We're a bit spoiled with the Prusa and perhaps become a bit complacent. Although well built, the Prusa printers do require occasional maintenance and safety checks. The difference is we can contact support and expect replacements when we encounter problems.

RE: This could have ended with a house fire...

With all due respect, the inside of the plastic PSU cover is very much on the "not user servicable" side. Not only it contains exposed line voltage elements, it is rather cramped and requires careful disassembly even if the PSU is not already connected to the printer.

I can't imagine being able to get into it with the printer fully assembled and all cables ziptied according to the guide.

RE: This could have ended with a house fire...

The part that jumped out to me was "The first step was to remove the power supply from the frame ..." I'm all for making mods, but if I've made significant alterations to my device -- including removal and re-routing of electrical connections -- I'm not going to place the blame on the manufacturer, much less post with such a sensational subject. The connectors were presumably still under the clear cover, were they not? It's just a bit of a jump from "loose connector" to "house fire".

I know many enclosure builds include removal and outright re-cabling of electronics and the PSU. I'm not saying the connector was or wasn't loose before removal, and we have no way of knowing, but I would definitely check power connections when relocating a PSU. You've definitely gone beyond "user serviceable" at that point.