How is that possible in lcnc

I think external offset on the z would be the way to go to get this done. 

 

Maybe this could be a starting point?
github.com/scottalford75/LinuxCNC-3D-Pri.../master/compensation

Uses Python2 though.

The nice thing about using the deeper layer of linuxcnc is it gives you axis geometry error compensation as a bonus.

External offsets is a great way to hack in new behaviour to try out ideas.
Unfortunately the adage 'Don't let perfection get in the way of good enough' can be extended too far.

endlessly stacking external offsets hacks makes setting up linuxcnc much harder.

Well it's also not possible with Mach4

I do not know how Tony did it, but on my setup it's a complete fail and I never got it to work.

One year or so ago I tried it for the first time.
The wizard did not generate any usable map file at all.
I edited a map file by hand then - just to see it work.
Loaded it into Mach4, but the software completely ignored it.
Asked the support, but they could not find the problem.

As I saw Tony's video I tried it again.
New Mach4 version this time.
The wizard also failed. I got a lot of "no touch points" even though the probe indicated a correct touch at every probe point and the machine stopped z-feed.
Ok. Again I corrected the point file by hand and this time it worked: The z-axis followed the touched surface.
I contacted the support about the broken wizard and they sent me a new one.
Same result: Lots of "no touch points".
I did debugging and tests together with the support.
Result: They marked the ticket as "Resolved" without any comment or solution. Nice!

So the surface-following function works in Mach4 if you manage to get a map file in some way.
Btw: G-Code Ripper also fails in combination with Mach4 (it works fine with Mach3!). The results of the "probe-only" runs are as faulty as the ones of the Mach4 wizard. It's Mach4 that has a problem - not G-Code Ripper! Love that piece of software!

There are lots of other serious problems with Mach4 and I tended to switch to linuxcnc for quite a while. Now I think the time has come to roll up my sleeves and start over using linuxcnc.

Lothar

Aciera wrote:

Maybe this could be a starting point?
github.com/scottalford75/LinuxCNC-3D-Pri.../master/compensation

Uses Python2 though.

Yes, my compensation component does exactly this. Works great for 3D printer bed "leveling" and it should handle more irregular surface with a higher number of probe points.

I really need to upgrade my LinuxCNC version and move my tools to Python3. So little time, too many projects....

Here is a video showing this:

It's in German, but the youtube translate function covers most of it.

As said above it's done by the compensation function of linuxcnc.

Enjoy

Lothar