feed rate limited

furynick

I'm facing a strange problem with firmware 0.92.3 on Mega2560/RAMPS1.4(A4988) board, I'm trying to find motion limits so I set max feed rate intentionnaly high as shown in following M205 output :
EPR:2 75 115200 Baudrate
EPR:3 129 0.000 Filament printed [m]
EPR:2 125 0 Printer active [s]
EPR:2 79 0 Max. inactive time [ms,0=off]
EPR:2 83 360000 Stop stepper after inactivity [ms,0=off]
EPR:3 3 800.0000 X-axis steps per mm
EPR:3 7 800.0000 Y-axis steps per mm
EPR:3 11 640.0000 Z-axis steps per mm
EPR:3 15 100.000 X-axis max. feedrate [mm/s]
EPR:3 19 100.000 Y-axis max. feedrate [mm/s]
EPR:3 23 2.000 Z-axis max. feedrate [mm/s]
EPR:3 27 20.000 X-axis homing feedrate [mm/s]
EPR:3 31 20.000 Y-axis homing feedrate [mm/s]
EPR:3 35 2.000 Z-axis homing feedrate [mm/s]
EPR:3 39 4.000 Max. jerk [mm/s]
EPR:3 47 0.300 Max. Z-jerk [mm/s]
EPR:3 133 0.000 X home pos [mm]
EPR:3 137 0.000 Y home pos [mm]
EPR:3 141 0.000 Z home pos [mm]
EPR:3 145 210.000 X max length [mm]
EPR:3 149 210.000 Y max length [mm]
EPR:3 153 250.000 Z max length [mm]
EPR:3 51 2000.000 X-axis acceleration [mm/s^2]
EPR:3 55 1000.000 Y-axis acceleration [mm/s^2]
EPR:3 59 80.000 Z-axis acceleration [mm/s^2]
EPR:3 63 2000.000 X-axis travel acceleration [mm/s^2]
EPR:3 67 1000.000 Y-axis travel acceleration [mm/s^2]
EPR:3 71 80.000 Z-axis travel acceleration [mm/s^2]
EPR:3 808 0.000 Z-probe height [mm]
EPR:3 929 10.000 Max. z-probe - bed dist. [mm]
EPR:3 812 2.000 Z-probe speed [mm/s]
EPR:3 840 30.000 Z-probe x-y-speed [mm/s]
EPR:3 800 0.000 Z-probe offset x [mm]
EPR:3 804 0.000 Z-probe offset y [mm]
EPR:3 816 20.000 Z-probe X1
EPR:3 820 20.000 Z-probe Y1
EPR:3 824 190.000 Z-probe X2
EPR:3 828 20.000 Z-probe Y2
EPR:3 832 100.000 Z-probe X3
EPR:3 836 190.000 Z-probe Y3
EPR:0 880 0 Autolevel active (1/0)
EPR:0 106 0 Bed Heat Manager [0-3]
EPR:0 107 255 Bed PID drive max
EPR:0 124 80 Bed PID drive min
EPR:3 108 196.000 Bed PID P-gain
EPR:3 112 33.000 Bed PID I-gain
EPR:3 116 290.000 Bed PID D-gain
EPR:0 120 255 Bed PID max value [0-255]
EPR:3 200 2200.000 Extr.1 steps per mm
EPR:3 204 10.000 Extr.1 max. feedrate [mm/s]
EPR:3 208 4.500 Extr.1 start feedrate [mm/s]
EPR:3 212 500.000 Extr.1 acceleration [mm/s^2]
EPR:0 216 3 Extr.1 heat manager [0-3]
EPR:0 217 230 Extr.1 PID drive max
EPR:0 245 40 Extr.1 PID drive min
EPR:3 218 7.0000 Extr.1 PID P-gain/dead-time
EPR:3 222 2.0000 Extr.1 PID I-gain
EPR:3 226 40.0000 Extr.1 PID D-gain
EPR:0 230 255 Extr.1 PID max value [0-255]
EPR:2 231 0 Extr.1 X-offset [steps]
EPR:2 235 0 Extr.1 Y-offset [steps]
EPR:1 239 1 Extr.1 temp. stabilize time [s]
EPR:1 250 170 Extr.1 temp. for retraction when heating [C]
EPR:1 252 4 Extr.1 distance to retract when heating [mm]
EPR:0 254 255 Extr.1 extruder cooler speed [0-255]

Even with these parameters I can't go faster than about 49mm/s with commands like G1 X150 F4800.
I can hear sound difference until F2940 but no more speed even with F9999 ... did I missed something ?

Thanks for you help,
Nicolas.

Repetier

Yes, you missed you are using a Mega 2560 which has limited speed. 800 steps per mm * 100mm/s = 80000 mm/s. Limit you can reach with that processor is around 40KHz. Reduce resolution if you want to go faster. Alternatively switch to Arduino Due + RADDS shield, then you can achieve 300-400KHz.

BTW: Speed limit 100 is not much if your head is not very heavy. 200-400 is normally possible from the motor side. Not that it makes sense to print that fast:-)

furynick

Thanks, going down to 400 steps/mm and give it a try.