A 3$3D printed CNC probe tool for surface scanning

This weekends miniproject was creating a probe tool for my CNC. The tool is designed in Onshape and the files are available there if you want to tweak the design. You can also download the STL files directly from thingiverse.

Video below shows how the probe works. When the probe hits the surface of the workpiece the rod will be pushed upwards and hit the stop switch. When the spindle liftes up the spring will push the probe back to original position.

Onshape design snapshot

It took me a couple of prints before I landed on the current design. To make it you obviously need a 3d printer, and in addition some hardware;

* end stop switch
* LM8UU bearing
* 8mm spring
* 6mm bolt (minimum 40mm length)
* I also thought about using a 8mm steel rod for the main part going through the bearing but ended up using a 3D printed part instead.

With some rough calculation this probe tool costed me a couple of dollars - max 3 if I also include the 2 failed design prints of the probe tool ☺

The cool thing about this design is that you can perform probing of an uneven surface thus enabling CNC jobs such as cutting or carving to follow the curves of the workpiece. Other probing tools depend on having electric conductive surface tape (e.g aluminium) on the workpiece - this is not needed with the probe tool since it uses a switch instead.

You can find the design here on Onshape: click here
I have designed it so that you can switch the tip - for softer materials it could be beneficial to have rounded end - for harder materials a pointed end (more accurate).

As a test I tried it on the shaft of an old axe I had lying around - really promising results! Here I also used a rounded end so I expected lower accuracy. Still really nice - in the video you can see how the gcode is adjusted for the uneven surface of the axe (you will notice the Z movement during carving). Cool. Dig it. This is going to be a nice add-on to my beloved CNC ☺☺

Here you see the probing in action - there was differences on the surface of about 3-4mm. I scanned it with a 10mm grid (10mm between each measuring point). Smaller grids == more accurate and time consuming.

I use Estlcam for controller and CAM. Estlcam supports surface scanning - so this is a perfect fit for me. Not sure what Mach3 can do but sure there are add-ons for it as well? I also believe ChiliPeppr has the same functionality. The way it works is that you send the design to machining and then perform the surface scanning. When the scanning is complete the program will reload - adjusting the gcode with the Z axis movements needed to cater for variances in height on the workpiece.

And here is the end result

If you have any questions feel free to drop me a mail or leave a comment below. Happy making folks!


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