Z-Axis correctly homing but crashes into the endstop on printing

dc42

It's normal for the homing switches to be ignored except when homing, not just in RRF but in most other firmwares too. The soft endstops set by M208 limit the motion after homing.

Jackal

https://duet3d.com/wiki/G-code#G0_.26_G1:_Move
The G1 g-code is for moving, so if you send a move via Machine Control or while printing it usually does not include the S parameter that's why it ignore the endstops.
There is nothing wrong with your homing.

CoolM8

But why then does the bed crash into the enstop and the print head is not able to move when i start a print? This all happens after homing.

dc42

Did you see my earlier reply? https://www.duet3d.com/forum/thread.php?pid=11931#p11931

CoolM8

Yes, the home all works all fine as i already mentionend. Homing the axes indivdually works just fine too. Only when i start a print it homes first just fine and then it moves the printing-plate into positon where it crashes ito the nozzle beacuse it is not stopping correctly anymore.

dc42

Please post the first ~50 lines from the gcode file you are trying to print.

CoolM8

Here it is (it is generated with Cura 2.4):

[[language]]
;FLAVOR:RepRap
;TIME:26015
;Filament used: 13.6328m
;Layer height: 0.15
;Generated with Cura_SteamEngine 2.4.0
M190 S70
M104 S245
M109 S245
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F9000 ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E6 ;extrude 6 mm of feed stock
G92 E0 ;zero the extruded length again
G1 F9000
;Put printing message on LCD screen
M117 Printing...
;LAYER_COUNT:199
;LAYER:0
M107
G1 F1500 E-6.5
G0 F3600 X86.3 Y86.301 Z0.3
;TYPE:SKIRT
G1 F1500 E0
G1 F1800 X86.3 Y97.501 E0.21068
G1 X86.26 Y98.29 E0.22554
G1 X86.141 Y99.07 E0.24038
G1 X85.943 Y99.835 E0.25525
G1 X85.669 Y100.575 E0.27009
G1 X85.321 Y101.284 E0.28495
G1 X84.903 Y101.955 E0.29982
G1 X84.478 Y102.504 E0.31288
G1 X84.666 Y102.722 E0.31829
G1 X85.117 Y103.37 E0.33314
G1 X85.501 Y104.061 E0.34801
G1 X85.813 Y104.786 E0.36286
G1 X86.05 Y105.539 E0.37771
G1 X86.209 Y106.313 E0.39257
G1 X86.29 Y107.098 E0.40742
G1 X86.3 Y107.5 E0.41498
G1 X86.3 Y118.7 E0.62566
G1 X97.5 Y118.7 E0.83634
G1 X98.289 Y118.74 E0.8512
G1 X99.069 Y118.859 E0.86604
G1 X99.834 Y119.057 E0.8809
G1 X100.574 Y119.331 E0.89575

dc42

So your start gcode is homing xy then homing Z. What happens if you send these commands manually:

G28 X0 Y0
G28 Z0
G0 Z0.3

CoolM8

This works just as fine.

timcurtis67

What is the "G1 F9000" for?

Its in this section of the program
G92 E0 ;zero the extruded length again
G1 F9000

Maybe that is causing the crash?

deckingman

My best guess would be as follows but I'd need to know what maximum speed you've set for Z in your config.g.

Towards the start of your gcode, there is G1 Z15.0 F9000. That is to say, move the Z axis 15mm at a speed of 9,000 mm/min which is pretty dammed high for the Z axis - it's 150mm per second and if you are using some sort of lead screws, I'd doubt that the machine is capable of that speed. So, you'll likely have skipped steps and the machine won't physically move that 15mm. So say for example that it only moves 10mm but the electronics "thinks" the bed is at 15mm away from Z=0. The next Z move is to go to 0.3mm at a speed of 3600 (still high IMO but more sensible). So the machine "thinks" it has to move the bed 14.7 mm to get to Z=0.3 but because the bed is only 10mm away from the nozzle, it'll crash.

It's easy to check - just edit that Z15.0 F9000 to something like Z15.0 F600.

AFAIK, the maximum speed you set in config.g should also limit the speed regardless of what the slicer tries to do (DC42 will confirm this or otherwise) so if you have that set high, reduce it to something sensible.

HTH

CoolM8

Nope Z15.0 F600 and Z0.3 F600 still give the same result. Because my Machine is an Ultimaker Original and rhe Profile in Cura is for the Ultimaker Original it should be able to do F9000.

deckingman

Oh well, it was just a thought (although I'd be amazed if your Z can travel at 150mm/sec). However, you've tried a slower speed so…...

The only other thing that I can think of is are you sure you've got the steps per mm correct for Z? What do you have them set to and what is the lead (not pitch) of your screws?

Edit, even if your machine is capable of 9000mm/min in Z , it's way too fast IMO - especially if you are using that sort of speed to home.

timcurtis67

I see what you are saying but if you look close in the program you posted you just have a "G1 F9000". No axis is called out on that line. I would remove that line and see if it corrects the crashing issue.

This is where a single block button would be nice to have. All of the CNC machine I run have that switch to step through the program one line at a time. Its a big help for correcting program issues.

CoolM8

No this doesn't work neither. Im gettig so frustrated, it all homes fine wen it starts the g-code file, then it moves to the center in X and Y and then it moves the Z-axis (I've even increaten from Z0.3 to Z0.6) but is still can watch how the platform hits the Z-axis enstop but carelessly continues to move upwards.

deckingman

Just to be clear. If you home Z, then do G1 Z0 does it go to the point where the nozzle is just touching the bed?

timcurtis67

@CoolM8:

starts the g-code file, then it moves to the center in X and Y and then it moves the Z-axis (I've even increaten from Z0.3 to Z0.6) but is still can watch how the platform hits the Z-axis enstop but carelessly continues to move upwards.

Anyway you can post a video of this happening?

Is your Z home position down at the print bed where the nozzle touches the build plate or up with the nozzle at it highest point away from the build plate?

CoolM8

Here is a short video. You can clearly see that i the beginning the Z-axis correctly stops when the endstop triggers, but when it moves to the middle you can hear that the Z-axis turns further even though the endstop triggers.
https://youtu.be/93f6WJ-Ht1I

This is the test G-Code file:

[[language]]
;Generated with Cura_SteamEngine 2.4.0
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 X0 Y0 ;move X/Y to min endstops
G28 Z0 ;move Z to min endstops
G1 Z15.0 F600 ;move the platform down 15mm
G92 E0 ;zero the extruded length
G1 F200 E6 ;extrude 6 mm of feed stock
G92 E0 ;zero the extruded length again
;Put printing message on LCD screen
M117 Printing...
;LAYER_COUNT:199
;LAYER:0
M107
G1 F1500 E-6.5
G0 F3600 X86.3 Y86.301 
G0 F600 Z0.6
;End of Gcode

T3P3Tony

What is in your homing gcode files?

CoolM8

[[language]]
; homeall.g
; called to home all axes
;
; generated by RepRapFirmware Configuration Tool on Thu Nov 17 2016 21:40:07 GMT+0100 (W. Europe Standard Time)

; Relative positioning
G91

; Lift Z
G1 Z5 F6000

; Move towards X and Y axis endstops (first pass)
G1 X-215 Y-215 F1800 S1

; Go back a few mm
G1 X5 Y5 F6000

; Move slowly to axis endstops once more (second pass)
G1 X-215 Y-215 F360 S1

; Move Z down until the switch triggers
G1 Z-210 S1 F1800

; Absolute positioning
G90

; Tell the firmware where we are
G92 Z2.5

; Uncomment the following line to lift the nozzle after probing
;G1 Z5 F100

[[language]]
; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool on Thu Nov 17 2016 21:40:07 GMT+0100 (W. Europe Standard Time)

; Lift Z relatively to current position
G91
G1 Z5 F6000

; Move Z down until the switch triggers
G1 Z-210 S1 F1800

; Back to absolute positioning
G90

; Tell the firmware where we are
G92 Z2.5

; Uncomment the following lines to lift Z after probing
;G91
;G1 Z5 F100
;G90