This project https://hackaday.io/project/11583-odrive-high-performance-motor-control could be the power behind our CNC. No more steppers but cheap brushless dc motors could move our axes.
what kind of feedback is used from the motor? hall signals for commutation and an incremental (or absolute) optical encoder?
At the moment they use some sort of optical encoder. I guess in the future it will support a variety of encoders
I have to mention this little project as well https://hackaday.io/project/11224-mechaduino does the same trick, only using a stepper-motor as a BDC.
DJ’s BLDC drives are fully realized and open source. http://www.delorie.com/electronics/bldc/
Although most folks still won’t be able to cope with the level of sophistication. So it is all a white elephant to me.
anything I could retrofit to replace a nema17/23 stepper and stepper controllers with step+dir inputs?
Yes, that is the whole point of this project. Big industrial machines use servo motors. They are expensive, those hobbyking BDC motors are cheap and the controller should be around $ 50 for two motors. It is more expensive then a stepper motor and controller, but it is definitely cheaper than an industrial servor + controller.
But both projects named here say “CAN bus”. So where are the STEP+DIR inpute (+ESTOP output) to retrofit them onto a system that expectes to be connected to a dumb stepper driver?
The support a variety of options. You can configure these controllers over CAN, SPI. Or you can use them as input device. …
Very impressive, Wish my cnc could move that fast for laser work! I’ve worked in the Non Destructive Inspection business for over a decade. We commonly use Automated Ultrasonics for high accuracy scans. I was talking to the technician once about the motors and encoders they use. I was surprised to learn they use brushless dc servo motors not stepper motors. These motors move a 20lb frame with magnetic wheels vertically up a metal wall with high precision. Servo motors should not be discounted for hobby grade CNC, its what the commercial world is using.
@Matt_Herrera
servo motors are more expensive, and the control scheme is more complicated. Other than that though they do have excellent high speed performance. The high price, and complicated implementation is why they are largely discounted on the hobby scene.
Well I cant say I know too much about them, I thought they were cheaper but again I haven’t spent much time looking into them. I wouldn’t mind paying a little bit more for a laser CNC system that could move accurately and fast. @Paul_Frederick
@Matt_Herrera
often the price difference is quite a bit more than a little bit. But the pay off is that setup right servos can act like how one would expect an electric motor system to work. As opposed to steppers that are rather counterintuitive in their operation.