Has anyone tackled spindle speeds?
The post process, I see “M84 S12000”. But my spindle is controlled with PWM, 0-255, where 255 is around 12000 RPM. I could put the spindle speed in Fusion to 255, but that would mess up the feed calculations.
Is this something tackled in the Marlin firmware perhaps where I say 12,000 RPM translates to a value of 255 PWM? I have not seen anything in guffy’s post processor.
I don’t personally have a spindle, but I have a guess on how this works based on the comments in the configuration_Adv.h file. First there is this section:
* Speed / Power can be set ('M3 S') and displayed in terms of:
* - PWM255 (S0 - S255)
* - PERCENT (S0 - S100)
* - RPM (S0 - S50000) Best for use with a spindle
#define CUTTER_POWER_UNIT PWM255
This implies to me that you select one of three ways that the S parameter can be interpreted at the time you compile Marlin. The above code is pulled from the V1 maintained Rambo firmware, so in that particular version, the S parameter is expected in the range of 0 to 255. If all you have is a spindle, my guess is that you would want to change the line to:
#define CUTTER_POWER_UNIT RPM
A bit below this define, there are two other defines that may play a role in how the RPM parameter is intrepreted:
#define SPEED_POWER_MIN 5000 // (RPM)
#define SPEED_POWER_MAX 30000 // (RPM) SuperPID router controller 0 - 30,000 RPM
My guess is that Marlin uses these to map the spindle speed into the PWM value output on the pin. Any ‘S’ value below 5000 in the g-code gets mapped to 0, and any ‘S’ value a above 30000 gets mapped to 255.
That’s awesome, thanks! I got it fixed up. Not sure on the lower end speed of the 500w spindle or how it maps but I think this will do nicely
There have been recent posts in the forums that @tjones99 found a bug in the RPM method. Check the Control Spindle RPM through RAMPS topic for the gory details. I don’t know whether the fix he describes has been incorporated into the Marlin codebase yet.
(edit to give credit where credit is due)
Thanks for the plug, but can’t take credit for that, @tjones99 found and fixed it. My thread is more about the hardware of connecting the RAMPS to the spindle’s PSU.