Strange Z axis moves..

Hi all,

I finish my first RepRapPro Mendel project. It is running on Sanguinololu 1.3a controler with Marlin filmware.

I configure steps per mm, I setup axis movement direction, endstops are also work perfect and all that basic stuffs to do.

The problems starts when I start to print my first object ( 10mm cube). I generate Gcode in Slic3r sw and import it into Pronterface SW.
The Gcode look like this:

; generated by Slic3r 0.9.5 on 2012-11-22 at 18:37:55

; layer_height = 0.25
; perimeters = 3
; top_solid_layers = 3
; bottom_solid_layers = 3
; fill_density = 0.4
; perimeter_speed = 70
; infill_speed = 100
; travel_speed = 110
; scale = 1
; nozzle_diameter = 0.5
; filament_diameter = 3
; extrusion_multiplier = 1
; perimeters extrusion width = 0.70mm
; infill extrusion width = 0.70mm
; first layer extrusion width = 0.53mm

M190 S80 ; wait for bed temperature to be reached
M104 S235 ; set temperature
G28 ; home all axes
M109 S235 ; wait for temperature to be reached
G90 ; use absolute coordinates
G21 ; set units to millimeters
G92 E0
M82 ; use absolute distances for extrusion
G1 F1800.000 E-1.00000
G92 E0
G1 Z0.300 F6600.000
G1 X85.003 Y88.240
G1 F1800.000 E1.00000
G1 X114.993 Y88.240 F1260.000 E2.10233
G1 X115.253 Y88.260 E2.11192
........
........

Machine sets home positions for all three axis is waiting for working temp for extrusion and bed...
After this Z axis goes UP in infinity, but once machine starts to print and it was like it was printing right object, but the problems was that the Z axis was 10cm from the bed???

It is like machine is looking for on point to stop and then to start printing..

What can be wrong? Please, help me...

Homing requires it to hit an end stop which will mark the 0 point on the z. I'd say your firmware has the forward/backwards the wrong way and is going up to find home instead of down. Theres and invert option in the configuration of sprinter.

Hope this helps. Also best way to test is to use the printrun application and step it positive and negative and see that it moves in the right direction.

Then there is the rotation z steps per mm. It elcould e way out for your machine.

You may have your firmware configured to home at max position instead of minimum.
Since gcode for first layer seems correct (G1 Z0.300 F6600.000) I can only assume that your firmware is mixed up on what the endstops represent.
Should be a line in your firmware that looks like
#define Z_HOME_DIR -1
Make sure it is -1 if you want the nozzle to be on the bed.
Also, like duttonw said, you might want to also look into the direction that your printer thinks +Z is, make sure that it is up.

Hi all,

For the Home direction of Z I must set like this : #define Z_HOME_DIR 1 , otherwise Z goes up when is looking for home position and not down in the way of the bad.

I also configure the steps per unit, The machine is doing the right distance:
#define DEFAULT_AXIS_STEPS_PER_UNIT {15.748,15.748,640,145.624}

Where can I check the Z axis direction? I try to do some tests , but without success.

It is quite strange, because in gcode is defined Z axis with G1 Z0.300 F6600.000; so the Z axis must find out this position.

Thanks in advance..

HI,

I thing, that I resolve the problem...

I try with #define INVERT_Z_DIR true // and I thing that is working right.

tomorrow I will try with first print..

Thanks for help..