What's the Tiny Touch Plate Neodymium Magnet for?


Let me try to explain in my best English;
It’s a matter of placing the bit rather close to the edge of the 3 axes touch plate.
The script needs to move far enough on the y/ x axis.
Say, you place the bit 2 cm of the edge, and in the script you move it 1 cm to probe the side, this will obviously not work.

If you probe, and set this axis to 0, and want to go back above the plate you need to move it far enough in the script to reach that Point (including the bit thickness). I believe it’s better to move it further to probe and go back to it’s origin, then saving time and use short distances.

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Btw, I figured out that the angular deviation measurement would be rather easy to implement using G68 command, however I believe it is not available in stock Marlin and I’m not (yet) clever enough to know how to implement this. :joy:


– Align work that is not exactly aligned to the coordinate system. For example, suppose you wanted to run without tramming in a fixture. If you can probe the fixture to determine its angle, you can apply a G68 to “zero out” that angle and then run the part program. This can reduce setup time by reducing the need to be accurate and trammed in.


Ah, got it! Thank you!

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I had ordered a 3-axes touch plate, and it arrived today.

I’m looking at the sample code you supplied.

One question I have is: shouldn’t the x and y axes sections have their own versions of the G92 command, that takes into account the thickness of the lip on the touch plate (amount by which it overhangs the material to grip it), and also takes into account the diameter of the bit?

For example, on Z axis, you have:

G92 Z14.0000
→ set your probe thickness, in my case 14mm, so Z0 is actually -14mm

And on this website’s instructions for the Tiny Touch Plate, it shows:

G92 Z0.5

So, wouldn’t the X and Y need a similar approach?

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One other question, this time regarding G38.2. Your comment says,

However, in this YouTube video I’m watching, link below, the man says the number after the Z is setting a limit on how far down the probe should be willing to go while looking for the target.

Is he wrong? Or is your comment of “define it’s location as 0” not being understood in the right sense?

Thanks for any help or clarification.

Here’s the video link: Are You Ready to Learn to Write GCode for Your Touch Plates? - YouTube

It’s around the 4:55 mark.

PS: You have great English! One interesting tidbit: a really odd quirk of English is that “apostrophe s” ('s) shows “possessive” except in the case of “it.” In the case of “it” the apostrophe means you want a contraction of “it is” — and to show possession, there should be no apostrophe. So “its” means possession, while “it’s” means “it is.” So the comment would be “define its location as 0.”

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you are right!
In my example I forgot to set the offset (?) of the wall thicknes, on Y & X axes :slight_smile: If understanding Gcode correctly, the probing sets the 0 point, but you will always need to take into account the thickness of the probe. In all 3 directions.

Sorry for that mistake, I am still learning :slight_smile:

But, I believe there are multiple ways to achieve the same thing. I can be totaly wrong, but I would imagine that the following commands might result in the same thing, I should check it one day.

G38.2 Z14


G38.2 Z0
G92 Z14.0000

Oh, Here you can find the Linux Gcode details on 38.2, and here the Marlin documentation of it.

I am going to take time to watch that clip, it´s interesting.
In my tests, if I raise Z to the max, and issue the command G38.2 Z0 it keeps going the total distance I want it, until I trigger the probe. So it could be that “0” is just an “unlimited” command. But I am going to test to be sure.

I can say for sure now, that if I first set G92 X0 Y0 Z0 , my probing wont go further then let´s say 2-3cm.

Thanks Douglas, that made me just a bit smarter today :slight_smile:

Ps, in case any one looks for info on the G68 command, I found that Marlin does not support it. But you can actually add new G commands to the firmware. It would be a matter of implementing the G68 code, and add a way to set variables in the script, based on few probes. Then you could rotate the whole Gcode script based on the angle of your workpiece.

@ Olivier

Thank you! You are amazing.

I think if I get a working script that includes the x and y axes sections have their own versions of the G92 command, I would be golden.

So, did this morning a test, and it seems I am wrong :slight_smile:
Using the first command, you´re probe isn´t moving downwards as it needs to be:

G38.2 Z-14

But this would give another issue, it would only drop 14mm from current Z zero point (just like described in that YT video).

Next, I noticed that depending on the fact if I zero-ed the Z axis in the menu, following command would not always work. Didn´t find the reason for that just yet;

G38.2 Z0

So I believe, that for probing Z, it would be best to measure you maximum Z height, say 400mm, then use this command:

G38.2 Z-500.000
G92 Z14.000

That way your Z keeps going down, without giving a timeout, no matter how far it is raised. That would be important when using a homing Z call, as I believe Z will be at his max (in the example 400).

To complete the script to use 3 axes probe, something like this would work I think (without homing, or setting zero xyz!);

G38.2 Z-400.000 ; Probe Z from max
G92 Z14.000 ; Set Probe offset to 14mm, thickness of probe
G00 Z19.000 F500 ; Move 5mm above probe
G00 X-30.000 ; Move 30mm on X
G00 Z-9.000 ; Drop Z 5mm so X probe can make contact
G38.2 X0 ; Probe X axis, if zero´d X then cahnge this to for example - 30.000
G92 X10.000 ; Set Probe offset to 10mm, thickness of probe
G00 Z19.000 F500 ; Move 5mm above probe
G00 X20.000 ; Go back to original starting point
G00 Y-30.000 ; Move 30mm on Y
G00 Z-9.000 ; Drop Z 5mm so X probe can make contact
G38.2 Y0 ; Probe Y axis, if zero´d Y then change this to for example - 30.000
G92 Y10.000 ; Set Probe offset to 10mm, thickness of probe
G00 Z19.000 F500 ; Move 5mm above probe
G00 Y20.000 ; Go back to original starting point

Going to see if I can get a cheap 3 axes probe somewhere in Europe. Scienci Labs uses fair prices, but shipping and import tax make this extremely costly.