Duet 0.8.5 DC42-fork - change Z hight during print?

Hi all,

sometimes it happens that I have to change Z0 during the print because I see that the first lines are either to far away or to close.
In the moment I stop the print and change via G31 the Z value, upload the config and start again with calibration.
The IR Probe is very accurate within 0.01-0.02mm, but the Endstops are 0.01-0.03mm. So it happend that Z0 is off by 0.05mm.
Not a big deal for larger Nozzles, but when you are printing with a 0.25mm Nozzle 0.05mm is deciding a good or bad first Layer.

Is there a way to change it in 0.025mm steps up or down via a makro or something? A button in the PanelDue or the Web Interface would be nice to correct while printing.

is there any command that changes Z in the way like Z=Z+0.025 or Z=Z-0.025 ?


thanx
Dirk

Edited 3 time(s). Last edit at 11/23/2015 08:47AM by critical_limit.

Yes you can do that. The simple way is that if the head is at e.g. Z=0.2mm for printing the first layer and you want to drop it by 0.025mm, send G92 Z0.225. Or to raise the nozzle by 0.025 mm, send G92 Z0.175.

I have it in mind to add a "relative" option to G92 so you don't need to know what the current height is. Meanwhile, here is a way to do it using macro buttons::

1. Set up your pause.g file in the usual way, something like this:

M83 ; relative extruder movement
G1 E-4 F2500 ; retract 4mm filament
G91 ; relative motion
G1 X0 Y0 F5000 ; move head out of the way

and your resume.g file is the usual way, e.g.:

G1 R1 Z2 F5000 ; move to 2mm above resume point
G1 R1 ; lower nozzle to resume point
M83
G1 E4 F2500 ; undo the retraction

Pressing the Pause button will move the head out of the way, and pressing the resume button will resume the print where it left off.

2. Set up macros to alter the Z=0 setting like this:

G90
G1 Z5
G92 Z5.025

That will reduce the Z=0 height by 0.025mm. To increase it by 0.025mm, use 4.975 instead of 5.025.

Then you can press Pause, then run either of these macros one or more times, then Resume. But don't use these buttons if the print has already reached 5mm.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Thanx David for the quick reply.

But moving the Z with one relative command isnt that a problem for the rest of the gcode? Its set in the beginning of the file to absolute values. When you send G92 during printing wouldnt it set to relative then for the rest of the print?
So you need always 2 commands, do you? First for moving the head up or down, second to go back to absolute mode?

hm, have to try that after print is finished.....

cheers
Dirk

PS: checked it few seconds ago. With G92 it´s working for the actual layer. But the next Layer is affected, because it is going to absolute Z which is commanded by the gcode. If I add 0.05 in the first Layer, the second is 0.05mm reduced. Isn´t there a way to change the complete Z so that all Layers that are following are affected? Hm, only in relative mode, right? but how to set only Z to relative and leave X and Y in absolute?

PPS: That doesnt work. Need a command to move the motors for the towers, not the Z hight itself. If we can add a value to x-tower, y-tower and z-tower it wont affect slicer settings and absolute coordinates. But how to move the towers instead of z-hight? Is there a M-code in your fork for this??

Edited 2 time(s). Last edit at 11/23/2015 10:45AM by critical_limit.

Dirk, please try again. I am confident that the solutions I have suggested will work. The essence is:

1. Have the nozzle at a known Z height.

2. Use the G92 command to tell the printer that it is at a slightly different height, thereby shifting the Z=0 position. On the next move, it will adjust the nozzle height accordingly. This change will be permanent for all layers.

One complication that I have thought of is that if you are using "lift Z" in your retraction settings, and you send a G92 command to set the height to first layer height +/- a bit while the head is lifted, then the setting will be wrong because the head isn't at the first layer height.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Yes, of course it works. Sorry for my bad english.

but you have to know the layerhight and enter the absolute value you want to have. If you print many different parts one after the other you often don´t rememebr the layerhigh or can´t have a look so fast.
What I mean was, that it would be nice to have a button or command or something like that which adds oder subs e.g. 0.01mm by one click. So you can adjust on the fly.

But that needs to be done outside the Gcode coordinate system as I understand right. If we could add or sub directly to the towers it will have no influence to the gcode and you dont have to remember absolute numbers and no typos can ruin your print.

If I remember right one of the others firmware has this feature. was it Marlin, smoothie? Have seen it before but cant remember.

Quote
critical_limit
Yes, of course it works. Sorry for my bad english.

but you have to know the layerhight and enter the absolute value you want to have. If you print many different parts one after the other you often don´t rememebr the layerhigh or can´t have a look so fast.

That's why I suggested the pause/run macro/resume procedure. With that, you don't need to know the layer height.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I agree, thats the best option at the moment.

But you know how critical it is to lift, pause and resume during the first layer. Specially when you use Filament which is not sticking like hell to the bed. Changing height during movement without lifting retracting, pausing etc is much safer.
Thats why I asked for such a function/command.
M114 is only reading. M401 and M402 are not available in reprap.
So I dont see a way to do it with the existing commands. Maybe you can think about a new M command in one of your next releases (and, of course, a button "Nozzle 0.01 down" Nozzle 0.01 up" in the Panel ;-) )

cheers