Calc offset nozzle to center for G55

Hi!
Setup:
Print-shuttle/plate with space for 2 printhead but for now only 1 installed. Each one is -15/+15mm in x from the real center of the "fly-shuttle"/"print-shuttle".

-When using the whole 700x700mm printing-surface the printer is using G54 and in the config.g the offset of the 1 extruder is working fine

-When using a smaller ca. 300x300mm printsurface on top of the big one, I configured a macro for the students to use G55 temporarily

Now comes the thing:

Everybody of course takes the nozzle as a reference to define the G55. Since the nozzle is 15mm shifted in x from the "real" center, I assume in my little macro, I have to add/subtract that one from the defined point since otherwise it is off by that amount?

dc42

You don't need to use G54/G55 to account for nozzle offsets. Just use G10 commands with no L parameter in config.g to declare the offsets of each tool. See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Tool_definition_section.

@dc42 said in Calc offset nozzle to center for G55:

You don't need to use G54/G55 to account for nozzle offsets. Just use G10 commands with no L parameter in config.g to declare the offsets of each tool. See https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Tool_definition_section.

Ah-thanks, and sorry at the same time: I guess I have wasted some of your time by not explaining it correct (english is only 2nd language for me, hard sometimes):

Attached a picture:

The students can themself put the "smaller" plate for the fabric-samples "on top" (with some double-sided tape) of the "standard-big-plate" and so, since nobody can say where they put it - if they want to put it overall, and not the big plate - they have to set themself G55-x&y-val-update and in a 2nd step G55-z-val-update whereever they want it... (thanks at this point again for the baby-step-feature with which they can adjust afterwards the correct height while printing when their interpretation of G55-z was some way off...)

The reason you cannot simply "glue" a smaller fabric-sample on the big plate is, they play with flexible filaments and their tension in x&y and tape or similar stuff does not hold the tension applied... This was our simplest idea to do the job (the fabric is wrapped around the table to apply tension), the clips are underneath to avoid a crash in x&y-movement...

So G55 is not used for the offset, this is in the config.g - I just wanted to be sure if I visually use a nozzle as reference that is 15mm of center when using G55, I have to adjust within G55 for those 15mm, correct?

dc42

@lb said in Calc offset nozzle to center for G55:

So G55 is not used for the offset, this is in the config.g - I just wanted to be sure if I visually use a nozzle as reference that is 15mm of center when using G55, I have to adjust within G55 for those 15mm, correct?

If you select a tool that uses that nozzle and then you use that nozzle as visual reference and move it around to find the correct G55 setting, then the nozzle offset correction is already applied; so you don't need to adjust G55 for that 15mm. However, if no tool is selected when you move the print head around but you still use that nozzle as visual reference, then you do need to adjust for that 15mm offset.

@dc42 said in Calc offset nozzle to center for G55:

@lb said in Calc offset nozzle to center for G55:

So G55 is not used for the offset, this is in the config.g - I just wanted to be sure if I visually use a nozzle as reference that is 15mm of center when using G55, I have to adjust within G55 for those 15mm, correct?

If you select a tool that uses that nozzle and then you use that nozzle as visual reference and move it around to find the correct G55 setting, then the nozzle offset correction is already applied; so you don't need to adjust G55 for that 15mm. However, if no tool is selected when you move the print head around but you still use that nozzle as visual reference, then you do need to adjust for that 15mm offset.

Thanks!
Means: I just put T0 or better G10 P0 in the macro and everything is fine?

dc42

T0 should do it. G10 P0 will just report the parameters for tool 0.

@dc42 said in Calc offset nozzle to center for G55:

T0 should do it. G10 P0 will just report the parameters for tool 0.

Thanks! (Ouch - 4 month of learning RRF-G-code and still missed that one...)

@dc42

I knew it: It worked for a few weeks and today they had a crash with G55. Long story short (I was not there but had to rely on oral witness, and we all know how good that is ) they homed the machine, put the small plate on the big table, zero'd that one out with G55, and for some reason moved further up in Z and then crashed into the nozzle of course...

On the original big plate with homing done in G54, after homing there should be the software-fence active which does not allow more then -0.5 in z, I can only assume and that is what I wanted to ask you, if within G55 the "upper z limit" is not re-adjusted but lies - in the case of the small plate 10cm - far away?

Improvements going through my head:

thinking about putting a 2nd "emergency" trigger on the printhead
resetting (temporarily) the z-trigger-height just those 0.5mm up and let it always stop every movement
only for x/y maybe G55 might be used, but for the z-axis everything stays in G54 for the axis-minima-maxima to be present...
Use stepper as endstop (new to me, have to fiddle into that...)
...

EDIT(a day later):
It wasn´t so bad. Nothing really bad happend, just the little heatbreak needs to be replaced because it is bend and after trying to straighten it again, it broke...

The thing was, that I didn´t zero out the additional (optional) csys G55, 65, ... after each upcycling (didn´t know the vals would be saved) so they moved somewhere where they shouldn´t...

Kicked out the G55 for z, regarding the z-axis everything needs to be now done in G54 to always have the "minimum/maximum axis limits" active! That worked. And since they do not really need the 400mm in Z anyway I just subtractet the z-axis by the 100mm the small additional table has to ca. 300mm which should be enough.

@dc42

Is there a simple approach - maybe in future Firmwarereleases - to zero out/reset all csys in the config-override.g when homing or restarting (I think homing would be enough? (Was my fault that I didn´t check, that the NIST-Standard, that you quote for following, on additional csys is that way, that they seem to have to get saved for next startup...) sorry for my bad english!

For now, all good: I might just zero all csys after G54 out either in the config.g or when homing... The trick with the homing I might put in the g-code-wiki, to remember people (like me ) that csys vals are saved in the confg-override.g