X-axis becomes less level as it is lowered
Hi. I'm hoping someone here can help me, as I've spent the whole weekend trying to understand what's going wrong.
I bought and assembled my mk3 prusa from kit about 8 months ago, and it has been working great the whole time. I've not printed anything for the last couple of weeks. When I tried to print, I noticed that my bed was not level, (noticed due to the first layer looking different on different parts of the bed). I tried Z, XYZ recalibrating etc, with no luck. I soon realised the issue is not in the bed levelling, but that my whole X-axis is ~1.5 mm lower on the right than on the left. The X-axis is perfectly level when at the very top of the Z-axis. As the gantry is lowered, the differences between the left and the right side slowly accumulate, until there's ~1.2mm difference between them at the lowest point. I've created a graph, lowering the gantry in 5mm steps using the "move-axis" command, and measuring the actual distance moved on the left and right side of the X-axis. The standard deviation of each 5mm step is 0.1mm on both sides, however, this error seems to accumulate to a substantial difference at the bottom.
Things I've tried:
- Disassembling the x-axis idelers and re-assembling
- Taking off both delrin trapezoidal nuts and re-mounting them.
- Releasing the slack on the dust cover at the Z-motors
- Checking that the threaded screws and smooth rods are parallel with the frame
I'm now out of ideas, and could really use some help!
Nope. It's supposed to be that way. The pulley on the right is bigger diameter - so the position is correct to make the belt level. If you want to check level, use a tool called, interestingly enough, a level.
I think you've misunderstood what my issue is. I'm not talking about the belt. I mean the level of my x-axis gantry is out. And yes, one could use a tool called a level to demonstrate this, but that is reliant on whatever the printer is standing on to be level with the earth! Therefore what I've done is measured both sides of the x-axis (top of each idler) with respect to the top of the frame, as I move the Z-axis down. What you can see from the graph, is at the highest Z position the gantry is perfectly level. As I start lowering the gantry, it accumulates a tilt. The observed tilt results in my nozzle being 1.5mm higher on the right side of the bed than on the left.
So, is one screw different than the other? That is what your description seems to say - one screw either turns faster than the other, or the pitch of the screw is different. I doubt it is screw pitch, but you could measure that easily. I guess your Einsy board could be radically defective and spin one motor faster than the other. I have no idea how that could happen unless the steppers are not the stock steppers.
But do consider what I said. Since the two axis are NOT designed to be level - orange part to orange part at the top - you may not have any issue at all. If your bed is not level, and the printer is assuming it is, try enabling 7x7 bed mesh leveling in settings - that is a feature designed to handle non-level situations with one assumption - the bed is reasonably flat (plane). The bed mesh leveling will detect the deviation you are describing and software will automatically change the motor spin accordingly on each side to accommodate.
I´d update the firmware first and then run a full first calibration like shown by JP here:
If that does not help I´d guess the Einsy or one of the steppers is toast, but there are others knowning much more about that.