I am having issues with the G28 command moving the Z-axis up in 20mm increments (the raise before homing value). The first move is faster than my steppers can move so they stall on my Prusa i3, running Ramps 1.4 using Kimbra Marlin 4.12 or 4.2 with 8825 drivers.

I have changed the homing values, below are the settings from my configuration_overall.h

#define HOMING_FEEDRATE {150*60, 150*60, 300, 0}
#define MANUAL_FEEDRATE {100*60, 100*60, 300, 60}
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, 800, 94.1, 625, 625, 625}
#define MICROSTEP_MODES {16, 16, 32, 16}
#define MOTOR_CURRENT {1, 1, 1, 1, 1, 1, 1}
#define DEFAULT_MAX_FEEDRATE {5000, 5000, 100, 200, 100, 100, 100}
#define DEFAULT_MAX_ACCELERATION {1000, 1000, 100, 5000, 3000, 3000, 3000}

I will kill power next time it happens and measure the distance moved. It almost appears that it is doubling the distances.

#define Z_RAISE_BEFORE_HOMING 20
#define Z_RAISE_BEFORE_PROBING 20

When it over drives the steppers it moved ~55mm up (more since the steppers stall).

Then other times it only moves ~15mm at a slow feedrate.

Then usually after a print a G28 moves the z-axis DOWN.

Edited 1 time(s). Last edit at 10/19/2015 09:28PM by randyf1965.

I am running 8mm acme lead screws from [openbuildspartstore.com] .

I have tried lowering my feedrate but at 10 the z-axis barely moves.

Tonight I removed the jumper on the Ramps board between Vcc and 5v and added a 7805 circuit to supply 5v to the Ramps seperate from the Arduino, same issue

Tomorrow I will try putting Octoprint back in the mix and see how it runs thru that instead of my pc.

Or I guess I could disconnect my PC from the printer and print from the sd card.

More troubleshooting and talking to myself......


ok, disconnected the pc and ran an autohome from the LCD... same issue. First time it moves way too fast and stalls the z-axis steppers, 2nd time works normal (WTF?!?!?!??!) and soi far everytime after that first try it works ... until I power cycle the arduino/ramps

Edited 1 time(s). Last edit at 10/21/2015 09:27PM by randyf1965.

Octoprint does the same thing, the 1st G28 moves Z way too fast.

Still having the same issues with the first G28 moving way too fast and too far

Are the signals at the microstepping pins on the stepper driver stable and do they correspond to the configured microstepping?

Have not checked the signals on the pins, but I reflashed my controller.


Now it works the 1st time :
>>>G28
SENDING:G28
echo: gcode_G28 >>>
echo: setup_for_endstop_move > enable_endstops(true)
echo: Raise Z (before homing) by 5.00 > (home_all_axis || homeZ) > destination: (0.00, 0.00, 5.00)
echo: >>> homeaxis(0)
echo: setup_for_endstop_move > enable_endstops(false)
echo: setup_for_endstop_move > enable_endstops(true)
echo: > TRIGGER ENDSTOP > current_position: (0.00, 0.00, 0.00)
echo: set_axis_is_at_home 0 > (home_offset[axis]==0.00) > current_position: (0.00, 0.00, 0.00)
echo: > AFTER set_axis_is_at_home > current_position: (0.00, 0.00, 0.00)
echo: <<< homeaxis(0)
echo: > homeX: (0.00, 0.00, 0.00)
echo: >>> homeaxis(1)
echo: setup_for_endstop_move > enable_endstops(false)
echo: setup_for_endstop_move > enable_endstops(true)
echo: > TRIGGER ENDSTOP > current_position: (0.00, 0.00, 0.00)
echo: set_axis_is_at_home 1 > (home_offset[axis]==0.00) > current_position: (0.00, 0.00, 0.00)
echo: > AFTER set_axis_is_at_home > current_position: (0.00, 0.00, 0.00)
echo: <<< homeaxis(1)
echo: > homeY: (0.00, 0.00, 0.00)
echo: >>> homeaxis(2)
echo: deploy_z_probe > current_position: (0.00, 0.00, 0.00)
echo: setup_for_endstop_move > enable_endstops(false)
echo: setup_for_endstop_move > enable_endstops(true)
echo: > TRIGGER ENDSTOP > current_position: (0.00, 0.00, 0.00)
echo: set_axis_is_at_home 2 > (home_offset[axis]==0.00) > current_position: (0.00, 0.00, 8.41)
echo: > AFTER set_axis_is_at_home > current_position: (0.00, 0.00, 8.41)
echo: > SERVO_LEVELING > stow_z_probe
echo: stow_z_probe > current_position: (0.00, 0.00, 8.41)
echo: Raise Z (after) by 5.00
echo: > SERVO_ENDSTOPS > do_blocking_move_to_z 13.41
echo: do_blocking_move_to: (0.00, 0.00, 13.41)
echo: <<< homeaxis(2)
echo: > (home_all_axis || homeZ) > final: (0.00, 0.00, 13.41)
echo: setup_for_endstop_move > enable_endstops(false)

But the 2nd time it moves down instead of up unless I do a G92 Z0:

>>>G28
SENDING:G28
echo: gcode_G28 >>>
echo: setup_for_endstop_move > enable_endstops(true)
echo: Raise Z (before homing) by 5.00 > (home_all_axis || homeZ) > destination: (0.00, 0.00, 5.00)
echo: >>> homeaxis(0)
echo: setup_for_endstop_move > enable_endstops(false)
echo: setup_for_endstop_move > enable_endstops(true)
echo: > TRIGGER ENDSTOP > current_position: (0.00, 0.00, 13.41)
echo: set_axis_is_at_home 0 > (home_offset[axis]==0.00) > current_position: (0.00, 0.00, 13.41)
echo: > AFTER set_axis_is_at_home > current_position: (0.00, 0.00, 13.41)
echo: <<< homeaxis(0)
echo: > homeX: (0.00, 0.00, 13.41)
echo: >>> homeaxis(1)
echo: setup_for_endstop_move > enable_endstops(false)
Reset.
echo: setup_for_endstop_move > enable_endstops(true)
echo: > TRIGGER ENDSTOP > current_position: (0.00, 0.00, 13.41)
echo: set_axis_is_at_home 1 > (home_offset[axis]==0.00) > current_position: (0.00, 0.00, 13.41)
echo: > AFTER set_axis_is_at_home > current_position: (0.00, 0.00, 13.41)
echo: <<< homeaxis(1)
echo: > homeY: (0.00, 0.00, 13.41)
echo: >>> homeaxis(2)
echo: deploy_z_probe > current_position: (0.00, 0.00, 0.00)
start THIS IS WHERE I RESET since the extruder is trying to drive thru the hot bed

Similar behaviouring on our big deltas ( RichCattell's marlin)
Sometimes not always ( more often when homing after print finish ) it goes up stuttering.

If it is moving to fast, set the feed rates lower.

I resolved the too fast feedrates by using a M203 Z5 command followed by a M500 which sets the maximum feedrate on the Z axis to 5mm/sec or 300mm/min.

BUT I still have the sloped ABL the 3 layer skirt I print around my objects is ~.7mm thicker on the back side of the bed compared to the front.

Here is my latest G29 probing 4 points using a proximity detector on a 1/2" MIC6 aluminum bed.
The thickness of the skirt is still off by .09mm in 90mm front to back. The Z-Axis moves very slightly while printing.

Tonight I will try printing without bed leveling and see how it looks

Am I reading it correctly? The front left is low and the back right is high?

echo: G29 Auto Bed Leveling
echo: Bed X: 215.000 Y: 10.000 Z: -0.003
echo: Bed X: 42.000 Y: 10.000 Z: -0.110
echo: Bed X: 42.000 Y: 215.000 Z: -0.110
echo: Bed X: 215.000 Y: 215.000 Z: -0.170
echo: Eqn coefficients: a: 0.00013728 b: -0.00040854 d: -0.06980550
echo: Mean of sampled points: -0.09812500
echo: planeNormal x: -0.000137 y: 0.000409 z: 1.000000
echo: Bed Height Topography:
echo: +-----------+
echo: |...Back....|
echo: |Left..Right|
echo: |...Front...|
echo: +-----------+
echo: -0.01188 -0.07188
echo: -0.01188 +0.09562

echo: Corrected Bed Height vs. Bed Topology:
echo: +0.00168 -0.05832
echo: +0.00168 +0.10918

echo: Bed Level Correction Matrix:
echo: +1.000000 +0.000000 +0.000137
echo: +0.000000 +1.000000 -0.000409
echo: -0.000137 +0.000409 +1.000000