Z Safe Homing - is this the expected behavior?

I have just upgraded from 1.1.9 to 2.0.7.2. And as part of that, enabled Z Safe Homing.

This is what happens: when I do a G28, the X and Y are homing (X0, Y0). Then the probe is moving to the middle of the building plate, and then homing Z. That is all fine and it makes good sense. But then it just sits there…in the middle of the plate.

I would expect or would very much like the G28 process to finish with X and Y homing. That would be a normal G28, but in a safe way.

Am I missing any configuration, or is this behavior what I can expect from Z Safe Homing?

That is how it works. Remember, homing doesn't mean "move to 0,0,0", it means "find out where 0,0,0 is". Where the nozzle ends up is irrelevant to the homing process, as long as Marlin knows where the nozzle is at the end of it. If you want to move to 0,0 after homing Z, do "G0 X0 Y0" or "G28 X Y" after the initial "G28". Note that the latter may not end up at 0,0 either - if X_MIN_POS/Y_MIN_POS are negative (common on many printers) then the nozzle will be at a negative position as well.

X and Y always have to be homed before Z is homed - otherwise there is no way for Marlin to know where the Z_SAFE_HOMING position is.

Thank you for the explanation. I think the key here is that G28 does not mean ‘Move’ but ‘Find’. And in that perspective, it is doing what it is supposed to do. And we could just stop here.

However – from a normal user’s perspective, I think this is what happens most of the time: the Slicer software GUI has a ‘Home all’ button. That butten is in most cases used to ‘park’ the nossle. It is a very convenient way to do that, and really just a side effect of G28.

I would suggest a third option to the Configuration.h:

#if ENABLED(Z_SAFE_HOMING)
#define Z_SAFE_HOMING_X_POINT X_CENTER // X point for Z homing
#define Z_SAFE_HOMING_Y_POINT Y_CENTER // Y point for Z homing
//#define Z_SAFE_HOMING_ENDING_WITH_XY_HOMING // ending Z homing with X and Y homing
#endif

That would allow the option to ‘park’ the nossle pressing ‘Home all’ or just using G28.

Does it make sense, or is it an unreasonable feature request?

I have now made the code change myself. It works just as intended.
I think I will propose a feature request and share my code, then the community can choose to grab it or not.

That sounds like an excellent feature to make a pull request for. Just make sure you make your pull request against the bugfix-2.0.x branch, as documented in Contributing Code with Pull Requests.

Thank you for your support!

I am just a hobby programmer, and I would not dare to make a pull request. This is actually the first time I try to contribute to the community.
Instead I have now made the feature request (#21118) and provided the necessary information. My hope is that it will be assigned to some one that can do the proper testing and integration.

@MMcLure

Can I create a pull request directely on GitHub without installing GitHub Desktop, forking Marlin etc? (following the instructions in the link you send)
But basically just provide the same information as in feature request #21118?

I am asking as below is stated in the pull request form - and it seems to me that I can skip the Desktop/Forking part:
Will some else then embed the code into the bugfix-2.0.x branch for me?


<!--

Submitting a Pull Request

- Please fill out all sections of this form. You can delete the helpful comments.
- Pull Requests without clear information will take longer and may even be rejected.
- We get a high volume of submissions so please be patient during review.

-->

### Description

<!--

Clearly describe the submitted changes with lots of details. Include images where helpful. Initial reviewers may not be familiar with the subject, so be as thorough as possible. You can use MarkDown syntax to improve readability with bullet lists, code blocks, and so on. PREVIEW and fix up formatting before submitting.

-->

### Requirements

<!-- Does this PR require a specific board, LCD, etc.? -->

### Benefits

<!-- What does this PR fix or improve? -->

### Configurations

<!-- Attach Configurations ZIP and any other files needed to test this PR. -->

### Related Issues

<!-- Does this PR fix a bug or fulfill a Feature Request? Link related Issues here. -->

No - you definitely need to make a fork and a branch on that fork

Damn....then I am out of luck. I don´t have the guts to mess around with serious stuff like that. I will just wait to see if something happens.

Many thanks!