Yeah those new models aren’t shipping yet and I stay in touch with Zach over there. It does look like their new spindle is a little less protected.
Still not worried. I didn’t really cover the Modkita well and started having chip arcing inside from chips that got in through the top. Blew them out, no problem.
@gmack yeah the outer case is spinning. It is actually very well balanced and I was able to pump it up to 200watt output 
So the new one uses an out-runner too?
They are these guys:
https://www.digikey.com/product-detail/en/bourns-inc/PQ2617BHA-220K/PQ2617BHA-220K-ND/
I asked, currently waiting on a response.
Also what are your thoughts on this? Doonan has a tool load manager that will alarm out if not meeting the recorded or programmed spindle load. Makes me want to really establish some baselines .
Yep,
This is potentially valuable to Shapeoko / Nomad users. I think the thoughts on utility were that the VFD or Modkita controls would need to export the cutting torque back to the controller software, so probably CNCJS which knows which tools are running at that time. There’s lots of use of monitoring cutting torque to detect blunt or chipped tools on the big machining centers but knowing which tool and how hard it’s being run is a pre-requisite to doing this. A CNCJS plugin seems like the most achievable option.
The other thing that may well be useful, I think @Julien purchased something, is a wide band vibration sensor (well up into audio frequency at least 3kHz sampling) that we could use to detect when the spindle mount is vibrating unnaceptably because of some issue with the cutting.
I did, received it, played with it for 5 minutes before concluding that this module was not adequate for this usecase: it’s a simple shock sensor, which works with a little metal ball trapped in a cylinder. We need an actual vibration sensor (and this fell to the bottom of my priority list)
That’s good, ruling out options is a key step in finding the one(s) that work.
Simple “real time” spindle load (power), cutting force, and endmill deflection displays/meters seem like a “no-brainer” to me. I’m surprised that Bantam didn’t provide them in their new mill software. Maybe Carbide 3D will someday. 
Indeed, it would also be really nice to see, the next time the controller boards are updated, pin headers exposed for the stepper step / dir / enable signals so that people could use external drivers and closed loop steppers if they want to without having to junk the controller.
Good choice, inductance is measured at 100 kHz and an insignificant 2.5 mOhms. Should reduce ripple current without increasing required voltage.
@Vince.Fab’s VESC supports accelerometers, maybe he’d be interested in adding one to his Modkita? Maybe @CthulhuLabs could add one to his too? Another “real time” display/meter on the software GUI someday?
Then there’s this approach.
Only real problem I see with doing this is that my Arduino has about 10 feet of wires between it and the spindle. Accelerometers able to detect such vibrations have high data rates over SPI or I2C. Neither of which are really meant for runs on the same printed circuit board.
As for the VESC, I believe it is the hardware version 6 boards that support those.
My VESC should support three separate types of external IMUs. I believe the 6 has an internal IMU. Also I’m not quite following what your guys are talking about with inductors and ripple currents. Would it be possible to explain it in a simple way?
An inductor is effectively a coil of wire that impedes the flow of current (this includes the coils in a motor). With alternating current an inductor will shift the voltage and current sine waves of of phase with each other. The ODrive needs these two waveforms to be shift a minimum amount in order to do it’s calculations. The Makita router has a very low inductance so it might not be shifting the two waveforms enough. This might be why I get an unstable current when using the halls sensors.
Like in VFDs, the PWM frequency is much higher than the motor winding drive frequency that sets the rotation rate of the rotor. So, properly rated inductors can be put in series with the motor windings to block much of the (ripple) current at the PWM frequency while not negatively impacting motor performance. (The current thru inductors can’t change instantaneously, nor can the voltage across a capacitor.)
What gmack said. LOL
This current probe is accurate to 20kHz, but likely usable well beyond that for relative measurements (with and without the series inductors?) Do you know what the ODrive PWM frequency is?
It is running at 24kHz
That’s close enough to 20kHz that the current probe should be plenty accurate. With one of them connected to your scope, you should be able to easily see any 24kHz ripple component riding on top of motor winding commutation current. If you have one of those scopes that can do spectral analysis, you could also easily measure the difference in their magnitudes.
Quick off semi-topic question. I have one of the last belt drive Z access systems sold. I want to upgrade to either the Z-Plus or HDZ. Not sure which. Considering the experimentation I am doing with the Modkita and the desire to see how far I can go with that I am heavily leaning toward the HDZ. That said, I do not see myself milling aluminum in the near future as I live in an apartment (going to be buying a house in the next year) and do not want to piss off my neighbors. Also I have spent quite a bit more money on the Shapeoko than I originally planned so I am not sure I can justify the cost of the HDZ. Thoughts?
