Got it! I think the suggestion above is a good starting point. Check all connections are good. Look for wire breaks, may be hard to find. Another thing that is possible is solder joints failing but these will be hard to see without a large magnifying glass.
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The first time I had issues I actually replaced all the wiring with my own primary wire. I also bumped up all the gauges, so the 18 gauge wires are now 16 etc. The board itself actually doesn’t have wires directly soldered to it, it’s a mix of clip on connectors and screw terminals for the higher amp feeds. Thanks again btw guys for all the suggestions so far!
Could it possibly be your 120v supply power is having fluctuations or brownouts. I assume all the printers are running off the same line if they are on the same table. Brownouts and spikes can cause electronics to do strange things. Also could heat around the control boards be a problem? When I first started printing with my printer, I would get some random shifts, and assumed it was my z stepper overheating and missing steps. I removed the cover over the control board, and haven’t had a skip since. Recently I hooked a Raspberry PI with a t/c and recorded the temperature around the board. With the cover on it was running at least 5C hotter around the board.
Background info - or skip to questions at the bottom.
I had similar problems with 2 Ultimaker 2+ machines and one Lulzbot Taz 5. Only in the Z direction. At about 1cm in height, it would move the head down into the print instead of up. After a couple of layers, it would return to where it should be - except the print was broken loose and the damage was already done - I have some spectacular fails.
I spent the time to search through the gcode and found commands in the gcode to move the Z axis in the wrong direction.
When I switched off of using slic3r to using Cura, the problem went away.
So… Have you updated any software or firmware recently? What slicer are you using? Have you tried others? Can you backtrack and use older versions (if you did an update)?
Thanks for the reply!
They’re actually all on separate circuits. Just recently I had all the electrical in my garage re-done specifically for the printers and the business (Before, the one circuit for the garage also included the kitchen which included the fridge, and the furnace. The garage is also detached and the way the electrical was originally done was literally just a wire running from some outlet inside, then out about 4" under ground through the garden and to the garage)
As far as the motherboards overheating possibly, if that was the case then I don’t think the layers would re-align the way they do. I’ve had steps skip in the past but it always continues the print mis-aligned, it doesn’t go back to being perfectly aligned. Which leaves me to believe that it’s not the motors skipping, as for them to coincidentally be skipping out and perfectly back in again just doesn’t sound possible lol.
I’ll give it a check though, same with the faulty wiring mentioned as a possibility earlier, this whole issue just has me so baffled as it doesn’t clearly point to any one fault.
Just a ramps and arduino combo, trying to move away from these Melzi boards. Last time I tried this type of board, in fact it literally was this, I think I fried something. I can’t even count how many times I went through and double checked the wiring, when I plugged it in my PC connected to it, controlled it for a bit then smoke came up from it.