I have a 750x1000 Ooznest which has been running well, but the Y-Axis / Gantry has started noticeably stuttering / skipping steps during jogging. Tends to happen near the centre on the belt, at random. A gentle push in the direction of travel will stop it, and resisting movement will generally trigger it.
I think I have resolved this by loosening the eccentrics and re-tightening until just engaged and raising the frame off the bench onto a smaller piece of board. I was managing to do some long (300mm) jogs with no issue through the centre of the Y-axis (most problematic area)
I’m suspecting that the bench I have the Ox on is not flat and this is causing the Y-axis to not be parallel to each other.
Found this after a job failed due to missed steps. Thought I had reduced spindle speed too much (was seeing increased tool load, much better “chips”, lower noise)
Has anyone encountered this before?
Is there any thing else I should check before I start trying to cut again?
In the process I’ve also
tightened the Y-axis eccentrics
increased driver current (was on the low side to start with)
decreasing max velocity and max jerk ( no change in stuttering! )
checked, cleaned and re-tensioned the belts (multiple times)
raised the Y-axis steppes to the top of there adjustment range for better belt-pulley engagement.
tightened pulley grub screws (one pulley was very loose, plan to replace with M3 grub screws at some point)
With the machine off, does it move smoothly up and down the Y if you push it? Can you notice any change in resistance or is it smooth? Double check your max velocity and jerk. Slowing it down usually fixes the issue if there isn’t some obvious binding.
I did test with the machine off and steppers disconnected from the drivers and I did not notice any binding. I will retest this evening though.
I quartered the max velocity and jerk and was still having issues. It was running fine with the setting and I consider them conservative to start with, so I’m looking for something that could have changed since I configured it, such as moving it from the floor onto the workbench.
I ran the gantry back and forth a few times and could not locate any binding. I’m guessing I flexed the frame out of square. It has since performed almost flawlessly over the weekend, only missing steps when I dropped the spindle speed too low.
However I’ve discovered I’m likely running at half the current I thought I was, as the knock off step sticks I’m using have different current sense resistors that the calculations I did. So when I get the chance I’m going to crank the driver current up a lot more!
Are using the cnc xPro? By default it comes in slow decay mode. Which does cause some load noises at very low speeds. It can be switched into fast decay by using the solder jumpers on the back which makes it a lot smoother at slower speeds.