Hi all,
I have been working on a DIY CNC router for awhile and settled on using an SK8 192kV motor to power the spindle. I went this way because most of the chinese spindles operate at 24KRPM and that's way to high for most metal cutting. Hopefully I can get around 6KRRPM on a 36V system.
Just to flesh out some details...i have machined a bearing housing to support the actual spindle and will be coupling to the motor with HTD pulleys. Most of the cuts will be around 500W with a maximum of 1000W for safety margin, I know these motors aren't specifically designed for operating at peak loads for long periods.
I think the VESC may work but have some concerns. My main concern is that to me it seems like the input basically regulates power and not RPM; theoretically I need the reverse...i.e. regulate RPM and the VESC increase power as needed.
I would appreciate any feedback on ESC choice, I also looked at ODrive but only need a single channel of control.
Thanks for the help.
Hello!
I have done just what you are up to. First I used a YEP esc for two years and now I have a VESC 4.12 which is working like a charm for 2 years by now.
My setup is Mach4 with a simple break-out board.
ESS Smothstepper
Spindelmotor Turnigy Aerodrive SK3 6374 192kV (this motor does not have the hallsensors, which anyway only is used with very low rpm)
Powersupply is HP ESP120 51,4V and 57A max DC, with output voltage lowered to 45V.
The spindle is geared down with HTD pulleys 26/40.
About the VESC... VESC Tool 0.86 Firmware 3.33
In Motor Settings I use BLDC-mode, (not FOC-mode. FOC does not work well in my opinion) and PID Controllers
In the App settings I use PPM and ADC
The system responds to different requierements in torque very well and keeps the rpm virtually constant, both in low and high rpms.
The only negative I have to say about this type of spindledrive is that is a bit (rather much I would say) noisy so earprotection is used when I stand in front of my mill.
If you PM me I can send you some screenshots of my VESC settings which I think will ease this task.
Hi GunnarW,
Thanks for the response! I'm really glad to hear that someone else has done this; I have Mach3 now but may switch to LinuxCNC.
Are you using the spindle control system in Mach4 or is the VESC doing the heavy lifting?
What materials are you working with and what are your cutting parameters?
-TBartoletta
I don´t really understand what you mean with using the spindle control...
I give my wanted rpm request via the gcode to Mach, and VESC gets that information from the ESS/breakoutbord and acts upon it. I do not do anything manually although I can alter the rpm slightly via the override bars on the Mach-screen. If I want to do something manually I have to start the spindle by issuing for instance s3000 and start from the MDI screen.
The cutting data totally depends on cutting circumstances like work material, tool material, tool dimension and so on, so there is no "common cutting parameters". That is up to you to read, test and learn what your machine and tools are capable of and is giving the result you want. There are loads of calculators and recommendations on the net...
I work in most materials like wood, plastics, aluminium and steel of various qualities and mostly with solid carbide endmills with diameters from Ø1 to 16mm (mostly Ø3 to 8mm) which is what I have ER-collets for. I never use those "microcuts" you often see in highrpm hobbymachines but tend to take "normal" cuts, but that depends on the working conditions as I said...
Regards /Gunnar
About the spindle control, I have seen where the RPM is measured with a sensor and Mach uses that feedback in a PID loop to control the spindle (usually the breakout board has an analog output for this). But it sounds like you are doing exactly what I want to do, Mach tells the VESC go to xRPM and the VESC handles the rest.
Thanks again Gunnar.
-TBartoletta
Yes, but of course you have to do some tweaking in the parameters both in Mach and in VESC-tool to get the rpm you commanded in the gcode, but it is doable, and it is hopefully a onetime effort. You can, if you want to, add a sensor on the spindel and accommodate feedback. I do not have that but I use the analog output from the breakoutboard 0-10V which I take down to 0-3,3V (with a voltage divider consisting of two resistors) for the ADC on the VESC-board. I have not bothered yet to tweak it to get it result in the absolute correct rpm because cutting speeds are not that critical in hobbiebusiness which is what I use my machine for.
Regards /Gunnar