M203: Not Consistent?



  • Is it possible to make the use of the M203 units consistent?

    It seems to define max speeds in [mm/min] via the config.g file, but use [mm/s] in the console.

    I would prefer that it always used [mm/s], since that aligns with M205.


  • administrators

    M203 in RRF always takes values in mm/min. Currently, M203 without parameters reports the values in mm/sec but I could change it back to mm/min if users prefer that.



  • @dc42 said in M203: Not Consistent?:

    M203 in RRF always takes values in mm/min. Currently, M203 without parameters reports the values in mm/sec but I could change it back to mm/min if users prefer that.

    Sorry for confusing the subject. I thought I was seeing different behavior in config vs console, but I think that was actually related to jerk and M566 / M205

    Still, I think having the time unit in M201, M203, M204, M205 as seconds, would be more consistent. M203 still seems like the outlier here:

    M201 X4000.00 Y4000.00 Z1200.00 E4000.00               ; set max accelerations (mm/s^2)
    M203 X12000.00 Y12000.00 Z1800.00 E2400.00             ; set maximum speeds (mm/min)
    M204 P2500 T4000                                       ; set accelerations (mm/s^2)
    M205 X10 Y10 Z10 E4                                    ; set maximum instantaneous speed changes (mm/s)
    

  • administrators

    The reason that M203 and M566 are in mm/min is that mm/min is the standard speed unit in GCode, for example it's the units for the F parameter in G1, G2 and G3 commands. GCode was designed originally for CNC machines, which typically use slower feed rates that 3D printers.

    M203 has been specified as taking its parameters in mm/min since 2013. There are tens of thousands of machines running RepRapFirmware and specifying M203 machine limits in mm/min, so it would be too disruptive to change the units now. Whereras M205 was added much more recently.



  • @dc42 said in M203: Not Consistent?:

    The reason that M203 and M566 are in mm/min is that mm/min is the standard speed unit in GCode, for example it's the units for the F parameter in G1, G2 and G3 commands. GCode was designed originally for CNC machines, which typically use slower feed rates that 3D printers.

    M203 has been specified as taking its parameters in mm/min since 2013. There are tens of thousands of machines running RepRapFirmware and specifying M203 machine limits in mm/min, so it would be too disruptive to change the units now. Whereras M205 was added much more recently.

    That makes sense.


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