[Tryan15]

I apologize for the lame title but I am not exactly sure how to describe this behavior. This is a new custom conversion of a Mini-Mill using ballscrews and steppers. I'm driving Nema 23 269 oz/in steppers with 24 volts on 8825s. The electronics is a Protoneer running GRBL. Install and setup seemed to go OK. I know I could do a little more tuning on Steps/mm and I am still unsure about acceleration.
I am using bCNC on the RaspPi OS to drive the machine. Manual controls appear to work correctly - jogs jog - home homes.
For my first cut, I drew up a 50mm square pocket 10mm deep in Fusion 360 and used 2d adaptive in CAM to make the cut. I posted using the Fusion 360 "Grbl /grbl" processor.
When I run the job, the machine motion does not match the displayed path in bCNC, even cutting air. The adaptive starts with a ramp-in in a spiral motion. The machine initially moves the table in a circle, but then it will run only the X axis briefly and then only the Y or neither at all. All of this in the first 20 or 30 seconds of cut. If I run the machine with the spindle off, I hear electronic noise from the cabinet even when the table is not in motion.

I am brand new to this so I am sure I am missing something obvious. Does anyone have suggestions on where to start troubleshooting?

Thanks in advance,

Tim

[hfjbuis]

If your are using DRV8825 stepstic drivers, Your stepper current, probably 3A or more, is way to large. The driver gets to warm and turns off to prevent damage.

You could use external drivers (my choice), a cooling fan, larger heat sinks or a stepstick drivers that can deliver more power like the S109.

[Tryan15]

Thanks for the quick reply. Over-current protection sure sounds reasonable. I was thinking the small movements, especially when cutting air, would not have drawn a lot of current, but it fits the symptoms. I looked at external drivers when I started the build and chose the Protoneer partly because it easily supports them. What is your recommendation for drivers? The TB6600 clones appear to match my operation ranges buy I have read of a lot of negative experiences with them. Is there a better option out there that won't break the bank?

[hfjbuis]

I use TB6600 drivers on 2 lathes. I run them not higher than 24 volts to avoid losing steps due to electric resonance. All other options for better drivers like leadshine, will cost quit a lot more.

I think a TB6600 driver is worth a try if you
- can't reduce the stepper current
- cool the drivers with a blower
- make the heat sinks larger

You can connect external drivers in stead off the stepstick drivers using some dupont wires!