I have noticed the belts appear to get tighter as a print progress, I have particularly noticed it when I am doing multiple depth cuts in a long print. In the attached file I got a current exceeded warning and belts were very tight. I stopped the cut, manually deleted the lines up to where it had stopped, leaving the setup codes at the beginning and successfully completed the cut. Any ideas welcome.
[MSG:WARN: Motor current on Bottom Right axis exceeded threshold of 4000]
Stop Maslow and Gcode
Stop Maslow and Gcode
Iāll set it up and give it a go. I had also Released Tension and Applied Tension, before restarting. The print did restart in the right place, so I donāt think it had lost position.
I let run even after the warning. It finished the file, but then i couldnāt get it release tension until I powered off the Maslow and restarted. Then it came back unknown so I did the retract extend dance. Readings were meaningless.
All of those things seem like valuable and significant evidence about what is going on, but what exactly all the evidence is pointing to is a mystery to me.
Off the top of my head there are only two things which could be going on which lead to the tension going up over time.
The encoder is losing position somehow. That could be either a software or hardware thing, but the way to identify it would be to get a retract all which shows a significant offset at the end
The z-axis position is drifting. Because we compensate for the z-axis height when computing the belt lengths if the z-axis position is changing somehow that would lead to a change in belt tension.
The z-axis is a little tougher to diagnose because it is stepper motor driven so we donāt have any feedback on where it really is other than looking at it by hand.
If you look on the āFluidNCā tab you can see the āZmā readout which is the z-machine value which is the z-axis position independent of where the z-home is set. That value should match up with the real world measurement between the top of the stepper motor and the bottom of the router clamp, or if the router clamp is lowered all the way down it should read 0.
I think it time it might be useful to echo Zm in the Maslow display (maybe as something like āZabsoluteā?).
For validating Z - thereās a spare input that can be used for touch probes isnāt there? Could that be used for a limit switch as well (I should be able to fit a limit switch in the 1.1 version of the MonolithMaslow)?
If not Z missing steps - thereās no offsets or anything that can change over time that could be accumulating rounding errors or similar is there?
@BarbourSmith This one also displays Xm and Ym coordinates in addition to Ym, useful if trying to get a consistent position independent of where home is set, or setting home on a easily replicable basis. I know you can get it from the Control menu, but that is not convenient.
The z-axis position is drifting. Because we compensate for the z-axis
height when computing the belt lengths if the z-axis position is changing
somehow that would lead to a change in belt tension.
note that the Z axis is far more likely to skip steps when raising (fighting
gravity and belt tension) than when lowering.
tension would only be increasing if the Z height is higher than it thinks it is.
possible (and worth checking on), but doesnāt seem likely
