Hello, Im pretty new to CNC milling and I got a 1500x1500 cnc with an blackbox as controller. I bought it from a guy who build openbuilds. It is with lead screw and there is anti-backlash nuts. When I try making circles its not perfect. I have tried to tighten all the screws, but that didn't help. I have tried to calibrate the machine with the build in wizard in the openbuild controller. I have tried Fusion360, Aspire and another online program. I have looked at other forums and tried what they suggested, but nothing seem to work. In one of the forums I found a 100mm circel and when I run that gcode it looks perfect round. I hope someone can help me. I have contacted the guy I bought if from, but with no luck.
You have a little amount of backlash. It's in the axis that cuts left to right (or vice versa) in the picture you've posted. Backlash can have many reasons like belt not tight enough, if you have a belt. Set screw loose on the pulley and so on. Push comes to shove you can set the backlash in some programs, like Mach3 for an instance. Other programs may have that feature too.
The screws are probably ok, as long as you can't rattle them back and forth in their mounts. Did you tighten the anti-backlash nuts enough? The spring tension has to be high enough to keep the nut fully engaged under load in both directions. It's not a great system, but it's about the best you can do with lead screws.
Yes i did tighten the anti-backlash nuts - and I think they are enough. Can they be tighten to much? When I tested and tightened the screws today the left side on the y-axis did have problems with moving and the right side continued move. I was like the left side was too tight? Can the wheels be to tight or is it the anti-backlash nuts?
Wheels can absolutely be too tight, as can the anti-backlash nuts. They need to be tight enough to eliminate excess motion, but not so tight they can't actually do their job. The motors can definitely lose steps if they can't overcome the friction. NEMA 23s are relatively powerful, but they're not huge.
Double check the tiny little grub screws on the shaft couplers that connect the leadscrew to the motor Also make sure the setscrew on the motor side is positioned onto the flat of the D-shape of the motor shaft If not, or if they are a little loose, the coupler can slip on the leadscrew/motor shaft causing the backlash
I did find one of the setscrews that weren't on the flat side of the motor shaft and it did help a bit. They are still not perfect. I hope I can find some more to adjust so I get better circles.
