Z probe question

I used a z probe before I recently added duel endstops. It used to go to the surface and then back off and then slowly go back down to get a more accurate location. Now that I added the endstops, the endstops do a second check but the Z probe just quickly descends to the touch plate and doesn’t do a double check. This has resulted in a couple of times where the z is not properly determined and it cuts too low. Is this a normal thing or how would I go about getting the Z probe to do the double check?

I forgot to mention. I got the Rambo board and hardware all from Ryan and am using the auto home code that is on the machining basics page.

Mine just probes once… you can specify the probing speed… I have mine set fairly low (60? 40?)

Where is that setting at? Is that something I have to specify in g code settings when I tell it to auto home? Slowing that down would help me.

I’m not sure how you are probing I’m not familiar with the auto home code…
The probing command is here… so for example I would use something like this.

G38.2 F60 Z-1

Where 60 is the feedrate. After probing I do G92 Z0 to set that as the new zero height.

If you are doing Z homing that is a different thing.

Thanks. I was using G28 which is the auto home code but it doesn’t look like that allows me to change the speed. I’ll try using G28 for the X and Y and G38.2 for the Z so that I can lower the feedrate.

If anyone knows how to get the Z to home like the X and Y where it does it quickly and then backs off and then comes in slow I would like to know. If not, this should help eliminate it overshooting the Z probe.

Be careful the first time probing… by default probe will use the Z min endstop but it’s possible to set it up as a separate pin from the Z endstop.

I also have a separate Z endstop and it does the double touch Z homing thing.
You can compare to my config here… don’t just copy it though I have different hardware and pins.

You could also try fiddling with these settings:

* Multiple Probing
* You may get improved results by probing 2 or more times.
* With EXTRA_PROBING the more atypical reading(s) will be disregarded.
* A total of 2 does fast/slow probes with a weighted average.
* A total of 3 or more adds more slow probes, taking the average.
//#define EXTRA_PROBING 1

Something weird happened/changed. Mine all do the double tap on z probing and always have. Like you described, the first one is a bit quicker, touches, goes up a mm or few, then very very slowly comes back down. On older and newer firmware. I’m not sure if I’m caught up to the absolute newest right now though. I think my last firmware update was in the Feb-March area?

I don’t have any useful ideas on why yours changed but just confirming that is not normal, at least compared to how mine have always behaved.

This is a case of ‘probing’ and ‘homing’ being two different things in the 3d printing world, but kind of the same thing in the CNC world.

If your old setup didn’t have dual endstops, you would have been using your touch plate as an ‘endstop’, not as a ‘probe’. So when you home, Marlin treats your touchplate like a homing endstop switch and applies #define Z_HOME_BUMP_MM, which retracts then bumps again.

I’m assuming here but I think now you’ve got your dual endstops on your z axis doing that job, and a new ‘probe’. So when you do a ‘probe’ your are doing a different thing to a ‘home’.

So check your probing section in your config files, and make sure you have #define MULTIPLE_PROBING defined. Make a backup before messing with it, and only change one thing at a time.

@tailslide Are you saying you have two z endstops, and using a touchplate? I’m interested in how you have that wired, and if you get the double-touch on a G38.2 without multiple probing defined.

***EDIT I just saw I was in MPCNC not Lowrider, the endstops will be setup differently! @ijustlikemakingthing don’t mess with your probing, just check in configuration_adv that #define Z_HOME_BUMP_MM is defined

(just more details in case any of it is relevant)

I’ve always been on dual end stop firmware.

Homing X Y and Z have always all double tapped

G38.2 also double taps on all axis, but this one I might have configured. I can’t remember. I do remember I had to do some tinkering in the config.h’s to get this working the way I wanted for XYZ probing without messing up Z homing all while using the same probe.

Edited to add: I’m not trying to be disagreeable, mostly just curious if a firmware update changed/broke this because this isn’t how any of mine ever acted

I have a single Z endstop and a separate touchplate. I could setup a second Z endstop as well and wire my Z motors separately but I haven’t found the need on my lowrider.

On my setup I have the Z endstop connected to Z-min and Z probing connected to a different pin… I can’t remember what maybe Y max ?

I see the double touch on the Z endstop but not with G38.2. I don’t find the need on G38.2 since when I probe it’s generally close to the piece to begin with and I have the feedrate set slow where with homing you don’t know where the carriage is and it’s moving much faster on the first touch.

This is what I set to zero when I want to disable the double bump. There is a Z home speed in the configuration.h file as well. Either way, you’ll need to flash the firmware for these changes to have an effect.

So, what I’m getting is that this is a firmware thing? Would enyone know if the latest dual endstop firmware has the z “double bump” or will I have to learn how to edit the firmware to add it?

When I changed to dual endstops it was my first time flashing firmware so I could have done something wrong. That’s why I’m curious if the latest version has this function.

There are several ways you can mess up when flashing the firmware, but they almost all end up with an error message. It is very rare that you’ll end up getting close enough to actually change the firmware, but still make a mistake and change a setting.

Here is the bump setting in Ryan’s current Configuration_adv.h file. It is set to bump 2mm:

So if that’s also set to that in the Configuration_adv.h file that you used when flashing, then it isn’t the right setting to change.

I will try reflashing the firmware and see if that fixes it. It did the z bump with the firmware Ryan put on it and I didn’t change any settings so maybe I grabbed an older version or the wrong one when I flashed it to add the dual endstops.

Thanks for the help.

Thank you everyone. Just flashed the latest firmware and it now does the Z bump again.

I looked at the firmware I downloaded when I went to the dual endstops and it had the z home bump at 4mm so I have no idea what could have went wrong that resulted in my machine not doing it.

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