I’m working on my first MPCNC machine, and it’s coming along quite well. I’ll post some pictures in the next couple of days.
I have one new middle Z part left to print and should have that done tomorrow, then I’ll see how well the gantry goes together.
In the mean time I have X and Y motion working well, and have the Z Axis motor in its mount just sitting on the desk and have that working (sort of).
Running a UNO with a CNC shield.
I’ve added limit switches for X and Y and was playing with the Homing function ($H) in GRBL. For now I’m faking the Z Axis limit switch action manually.
When I issue the $H command the Z Axis starts spinning and when I pulse the Z Axis limit input on the CNC shield then X and Y move quickly to the limits and stay there until I pulse the Z Axis limit input again, then X and Y move to “center” and life appears to be good. Hard limits work fine too so things won’t crash and burn by trying to go past the physical limits.
Here’s the strangeness:
If I set the Homing seek ($20) in GRBL to 200 mm/min the X and Y axis appear to move just fine, but the Z stepper stutters, and doesn’t rotate smoothly.
If I drop the Homing seek to 120 mm/min then the Z stepper appears to rotate smoothly. GRBL uses the specified Homing seek rate for all 3 axis.
I haven’t tried swapping out the Z Axis stepper to see if there is something wrong with it. It appears to be wired correctly and is running smoothly at the slower rate.
I haven’t swapped the driver module, but I’ve tried different current settings low and high with no difference. I’ll try swapping the driver out first since that easier. If that doesn’t change things then I’ll swap the stepper out, but that will be more of a pain since don’t have a spare.
Note no micro-stepping involved at this point, and I need to fine tune things for the number of teeth on the pulleys, etc. This is just an early test to get everything working.
Has anyone seen something similar?
Is anyone using the Homing function with their MPCNC? If so where did you put the limit switch(es) for the Z Axis?
Thanks in advance,