I have a small problem and I would appreciate some opinions. Last night I started a print that was to take about 6.5 hours. Around the 5.5 hour mark I notice a loud violent “da-da-da-da-da” noise at the beginning of each layer. When I went to inspect the print I noticed each time I heard the noise it appeared to be shifting a few millimeters in the Y direction. I stopped the print and checked the Y belt and it seems pretty tight (maybe too tight". The only other thing I think it might be is the Y axis stepper motor may be getting hot. I have the top portion of my metal plus enclosed so the frame may have transferred the heat down to the board and Y axis stepper although the X and Z receive much more heat and don’t seem effect. Does anyone have an idea that I may have overlooked?
I would think most likely suspects would be the belt, pulleys, or else some kind of binding on the axis. I’d imagine the actual noise you were hearing was the teeth on the belt jumping on the pulley, so you may also want to visually inspect the teeth on the belt to see if they haven’t been worn down.
Have you done prints that were this tall before? It could be some kind of binding that only becomes an issue once the machine has reached a certain height.
I don’t think overheating would cause a problem like that, but anything is possible. Do you have an IR thermometer or anything like that which would let you quickly compare the temperatures of the different motors?
Yeah I would adjust your stepper current. (it would be a really minor adjustment in your case). Over time it can build up heat and skip steps of its getting too hot.
Also, sometimes the tip of the nozzle can catch briefly and cause skips or jumps if a high angle overhang curls upwards, but it doesn’t look like you’re having that issue.
That’s a good point, if the steppers are getting very hot you should look at adjusting the current on the board.
My first PrintrBot would overheat its Y stepper after printing for over an hour, and it turns out the current was set too high. In my case though, the got stepper would get slower and slower until it stalled.
Might have been teeth jumping, but for me that noise is usually the stepper skipping steps as it butts up against some kind of obstacle. Only happening at the beginning of each lay suggests something interfering with the movement of the nozzle rather than binding (but I could easily be wrong). One possibility is that your extrusion rate is just a touch too high, or your actual Z-movement just a touch too low, so that you don’t get any interference for shorter prints, but for taller ones the error adds up. You might want to measure that if you can.
I can eliminate it being a hot end obstruction because the point where it started a new layer was moving off the print in the Y direction more and more each layer. Stepper current could be the culprit. I saw video somewhere where a guy tweaked his stepper motor voltage on a ramps board with a multimeter. I assume its a software function on the printrboard? I don’t remember seeing any pots on it but I could be mistaken.
The newer printrboards, yep. Digital pots. You can set them with an M-command, and by default they’re not set particularly high. (At one point I cranked up my extruder current, and it solved some problems.)
Your dragon has a funky hairdo
@Mike_DiMare had a problem with the y bearings that is similar
It looked like he put on a ball cap. In fact that’s what I think I will do. Print a ball cap and glue it on.
Check your linear bearings. A da-da-da sound could be the bearings binding. Give them a quarter turn and check them again. Or replace.
I think digital pots are your best bet. Skipping steps (no harm to printer) sounds like grinding. The heat may be a factor.
Start with the basics, check the bearings, belts and pulleys first. I had something like this happen a few weeks ago and it was the Y axis bearings. Two of them had worn out from over a year of almost constant printing…
I had that last week, turned out it was due to a stray bit of plastic lying on the belt. I took it as a hint it was time to get the vacuum cleaner out and sort out my printer 
@Daniel_Bull That is my point exactly! Too many people start with the electronics (i.e. adjust the stepper voltage) before checking the basic mechanism.
@Keith_Applegarth yep, I’m guilty of that myself. I spent ages trying to figure out why midway through a print I had extrusion gaps. I changed temps, tested wiring, changed filament, printed at different speeds, looked at stepper currents, you name it. Turned out the grub screw on the extruder was loose.
Thanks to all. I checked the movement of the bed. It seems to move smoothly. I wiggled it in the X and Z direction and it has little to no slack so I assume it’s not the bearings. The belt on the other hand was super tight. Almost guitar string tight so I loosened it a bit. I will do a check print to see if it makes a difference and if it doesn’t on to the pots. Does anyone know if there is a tutorial on adjusting digital pots?
Check the bearings after it’s been going for a few hours, so everything is heated up.
Will do. Thanks again.
Belt tension. I’ve had this issue before too. At a certain point the X axis like to jerk big time! How I solved it was slower my speed and tighten my belts.