Touch Probe Madness

So I will briefly note my experiences which came today. I hope @robgrz and the rest of the team get to see this. None of this should be construed as ungrateful, as I think it is a great product, but a few things I noticed:

  1. Grounding. It was pretty obvious to me that the alligator clip had to be grounded in some way. I appreciate that there is a ring connection on the end so you can bolt it down, but I would warn people that the most obvious place probably won’t work. Many people are going to think that you can take out one of the bolts that hold the Y-axis rails to the base frame and simply use that to attach the ring connection to the machine. I tried, but as I suspected the powder coating prevents a good ground. I even tried in between the y-axis rail and frame, but it doesn’t make enough contact for a consistent ground. After a few tests, I figured out that the only place I could get a consistent ground was touching the aluminum plate that is the mounting bracket for the control board. So you can use the bolts that mount the plate to the X-rail (NOT the cover bolts) to attach it. That seems to be the only place I can get a consistent ground other than…
    DO NOT TRY THIS unless you are comfortable with electricity, picture below, but as a temporary measure I unplugged a standard three prong plug (this one goes to my computer monitor) and slipped the ring over the grounding prong and then plugged it in. There is enough clearance that it will not touch the hot or neutral prongs, but it still is not a good solution. I’m going to make my own separate ground connection off an outlet that will allow me to have a quick disconnect on the alligator cable instead of a ring.

  2. Finding a consistent ground should be the first thing in the assembly instructions and it is currently clear as mud. I recommend better instructions before the next batch of probes is released. Making sure you have a good ground and powering up the probe should be tested before you close up the cover on the control board.

  3. I have a 2.4d board and so I figured out that I didn’t need the adapter connector that comes with it for older boards, but I would recommend making that clear in instructions. I also recommend a short quick disconnect connection be added (which I am going to do on my own) so that I can leave a short pigtail out of the control box and connect / disconnect my probe with ease. I really don’t want more wires hanging out behind the machine.

  4. It is VERY easy until you get used to workflow to forget to alligator clip your end mill. This will result in your machine continuing to drive down into the probe without stopping (since there is no circuit completed). I did not damage the probe but I did a test case just for this fact and found it to be true. I recommend in a future update to CM 4 that something pop up on the screen to remind you to connect the alligator clip before beginning the probing cycle.

  5. The Z-probing, whether just probing for Z or doing a full X, Y, Z cycle seems very accurate. I tried it a bunch of times and could not come up with a scenario where it was off. I did not test it with a dial indicator, but it looks good to my calibrated eyeball.

  6. With regard to the X and Y probing I noticed the same issue as others. I did all my tests with the number #201 Carbide sold mill inserted. X and Y zero seem to be 1 diameter or so outside the edge of the work piece. I hope this is just a software calculation issue within CM 4. My understanding has always been that the exact centerline of the end mill should be centered over the origin in your coordinate plane.

  7. One odd note, you can see that when it sets Y to zero upon probing it consistently set it as .0030. I’m not sure if that is just a calculation thing, and inaccuracy in the tolerances of the probe, or something else. But if its a bug, I wanted to bring it up.

Pictures of some of my testing:
!DANGER WILL ROBINSON! Don’t electrocute yourself. No I’m not leaving my ground this way.

Coordinates after a full X,Y, Z probe cycle.

After an XYZ probe cycle, this is where 0,0,0 looks like in reality:

Looking down the Y-axis:

Looking down the X-axis:


You guys are amazing…

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User guide doesn’t help a program that inaccurately sets zero on XY axis.

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"NOTE: A mimimum clearance of 12mm is required between the material and the cutter "

“Position the cutter within 1/2” (12mm) above the top of the probe (as shown in the videos below).”

Does the positioning require a minimum of 12mm or a maximum of 12mm, I assume the later.

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I got mine today but didn’t get to set it up yet, but I’d like to maybe see a wizard or something built into the workflow that includes you touching the probe to the bit before you’re able to click the button to begin the probe sequence.


For anyone so interested, this is the link to when RichCournoyer tested the touch probe. We can compare how his testing went compared to the production models.

I would not be using the ground on the plug… pop it on an x/y rail screw, anything that connects to some bare aluminium.

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Rail screws and the plates aren’t bare metal. I put mine on the enclosure retaining screw but behind the enclosure. I.e. metal plate->ring terminal->enclosure->screw. Based on the size of the screw and the ring I think this is where it was intended to go.

Yes I know, regarding the grounding plug. Please re read my whole post. I did say I wasn’t using it as a permanent solution. But trust me, connecting it to the ground wire in my electrical outlet(s) circuit (via proper electrical wiring technique) is going to be the best ground available. And, as I already said, the only place I could find a consistent ground is on the aluminum mounting plate for the control board, but then you have a nice long wire permanently attached to your machine. You can easily back check me yourself. Plug in the touch probe and power on your machine, then hold the alligator clip against the probe. You can easily then use your other hand to test all the places a ground might work. X-Y rails are a no go. I tried many different locations.

Come to think of it wonder why the lead couldn’t plug into the probe and use it’s existing ground wire.

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Well, I’m now down a touch probe. After plugging it in and out a few times from the board to test different ways of running the wires, it stopped working. No power, no LED, nothing. Noticed that the connector on the board end was loose, so I cut back the shrink tubing to find the below picture. I popped the metal tab out of the plastic connector and tried to re-crimp the wire in there and reassemble. I could get the LED to light up and turn red when touching ground, but upon trying to run the probe cycle, it would just bring the mill down into the probe, turn the light red and then fail the cycle. Now I get no power or LED at all. I checked with a multi meter and I still have 5v coming out of the correct pin on the board, so I’m not positive but hoping that its not a control board issue. I think its a problem with the control board in the probe.

Email sent to support.

Please contact about this and we’ll work this out.

Bummer. Teething problems I guess. I forget if I mentioned it but I also lost the led functionality. Didn’t bother to look into it since I already had a replacement on the way.

Mine is fitted to my X axis side rail screw. Works a treat

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I know there’s a few threads on this, has anyone from c3d weighed in yet on whether the X/Y positioning being outside the edge and not centered on it is intentional or a bug? If it’s intentional it’d be nice to at least document where the software is intending to place the bit.

Hardware issues suck, hopefully that’s a fluke but it seems Griff had it out of the box and Evan quickly developed one :confused:

It worries me that no one from C3D has commented here yet. Kina curious if you ask me. I know they are reading this stuff.

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Check your alligator clips boys. Mind just failed after a morning worth of use, was getting intermittent red light. Glad I got into the habit of checking before I start a probe cycle

Wire pulled right out of the clip, it was only held in by the heat shrink tubing. Tiny blob of solder was all there was. Off to the solder station to fix that…

The wire is not crimped into the alligator clip, this offers zero mechanical protection from repeated use. A little glob of solder WILL FAIL rather quickly, this is not an “if”.

I crimped mine down and soldered it.

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I can’t imagine that is intentional… if you are using a corner probe to align multiple bits with different diameters this would cause them to be misaligned.

For example. Suppose that (0,0) is the corner of your material, using this routine a 10mm bit would be centered at (-5, -5) and a 4mm bit would be centered at (-2,-2).


Not saying I agree with the current method of having the bit tangent to the stock as opposed to over the corner, but…
When you change cutters you don’t re-zero X and Y, just Z. So going through the probe operation at the beginning will set the X and Y for the entire job. Each time you change bits you only reset the Z. The center line of the router will always stay the same regardless of bit size.

Not sure I can envision where you would reset X and Y after a tool change, but I probably have not run across that scenario yet.

I know, I’m giving them the benefit of the doubt is all.