VERY weird printing speed issue

Tinchus

Hi. Im tunning the printer to see what its limits are. So far I have been printing with acceleration values of 3000 in both X and Y and now Im tryng to raise those values.

My old config was like this regarding speed and accel:

M92 X80.16 Y80.16 Z1600 E428.25:428.25 ; set steps per mm
M566 X1000.00 Y1000.00 Z300.00 E450:450 P0 ; set maximum instantaneous speed changes (mm/min)
M203 X18000.00 Y18000.00 Z340.00 E2400.00 ; set maximum speeds (mm/min)
M201 X3000 Y3000.00 Z20 E1500.00 ; set accelerations (mm/s^2)
M204 P3000 T3000 ;
M906 X1500 Y1500 Z1200 E900:900 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S300 ; Set idle timeout

Now I just changed to this:

M92 X80.16 Y80.16 Z1600 E428.25:428.25 ; set steps per mm
M566 X1000.00 Y1000.00 Z300.00 E450:450 P0 ; set maximum instantaneous speed changes (mm/min)
M203 X18000.00 Y18000.00 Z340.00 E2400.00 ; set maximum speeds (mm/min)
M201 X4000 Y4000.00 Z20 E1500.00 ; set accelerations (mm/s^2)
M204 P4000 T4000 ;
M906 X1500 Y1500 Z1200 E900:900 I30 ; set motor currents (mA) and motor idle factor in per cent
M84 S300 ; Set idle timeout

The problem: I tried to print a sample test , same model and same printing settings. Now for example, the first layer with old config was being print at a requested speed of 20 mm/s and a real speed of 20 mm/s. With the new config, Im getting this weird behaviour: the first layer has a a requestd speed of 20 mm/s but I get a real speed of 2 and 3 mm/s !!!!

I have attached also the gcode, the speed there set for the forst layer is 20 mm/s so the speed is being re calculated by the firmware. What is happening here?

Thanks in advance for the help

test_pcABS.gcode

Phaedrux

Look at the start of your gcode file. You have a section of commands that is over writing your config.

M201 X4000 Y4000 Z300 E1500 ; sets maximum accelerations, mm/sec^2
M203 X18000 Y18000 Z500 E1000 I0; sets maximum feedrates, mm/min
M204 P4000 T4000 ; sets acceleration (P, T), mm/sec^2
M566 X25.00 Y25.00 Z5.60 E15.00 ; sets the jerk limits, mm/sec

Remember that M566 is actually in mm/MIN not mm/SEC

peter247

@tinchus I think you are using the Cura default start and end gcode which sets the acceleration and jerk.

Tinchus

@phaedrux Solvec, thank! I dont know where that gcode came from.... someting in the slicer has changed and that introduced that gcode.