M558 H parameter question

[fcwilt]

Hi,

I have a question about the H parameter for M558.

From the docs:

Hnnn Dive height (mm). The height above the trigger height from which probing starts.

In practice what does that mean?

Sometimes I can execute a G30 a good distance away from the bed and the probing shortly fails with an error message about the probe not being triggered.

Other times it travels much more than twice the dive height and eventually the probe is triggered.

I have not been able to determines what is causing the difference.

Can someone kindly enlightened this benighted soul? If my ignorance persists I may take to drinking heavily.

Thanks much.

Frederick

[dc42]

@fcwilt when you execute a G30 command with a P parameter and Z-999 or an even more negative value, or you execute G29 S0, then the probe moves to height H + max(probe trigger height, 0) above the expected trigger position.

[fcwilt]

@dc42 said in M558 H parameter question:

@fcwilt when you execute a G30 command with a P parameter and Z-999 or an even more negative value, or you execute G29 S0, then the probe moves to height H + max(probe trigger height, 0) above the expected trigger position.

Thanks.

But in these two cases it was a plain G30.

One time it probed "in mid-air" twice and reported a failure to trigger.

Another time it traveled 100+ mm and finally "found" the bed and triggered.

What is causing the difference in behavior? Some pre-existing state? I cannot figure it out.

Thanks much.

Frederick

[Phaedrux]

I don't think I've ever seen a G30 fail to trigger and I often have the bed at Z max (305mm) and my dive height is only 3mm. So there must be something else in play.

[fcwilt]

@phaedrux said in M558 H parameter question:

I don't think I've ever seen a G30 fail to trigger and I often have the bed at Z max (305mm) and my dive height is only 3mm. So there must be something else in play.

I agree but I have not be able to reproduce the odd behavior "on demand".

I will keep working at it.

Frederick