CCM Digitizing Arm - 5 axis Faro Arm

#1

When measuring physical objects sometimes calipers, squares, rulers and height gauges feel inadequate and accuracy is questionable depending on what you are measuring. I wanted a tool that can pick up any point in a 3 dimensional space and easily import into my CAD software of choice. I found an design by Nikolaj Møbius from FabLab RUC that got me pointed in the right direction for a cheap alternative to a $3000 want to have “problem”. A few other makers have made arms of various “quality” but there was no definitive guide that I could find. I started out modeling various methods of mounting the encoders and 3D printed 3 or 4 variations before coming up with a suitable setup that was ridged and repetitive in positioning.

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The finished 4 axis arm below is a repeatable and accurate (~0.2mm). Worked well, but did not give me the freedom that I want to have with the tip (end effector). The arm uses an Arduino to read the encoders with a serial connection to a computer where you can run a Processing sketch that gives you a visual representation of the 3d space and the ability to export point cloud and DXF model (both 3d and 2d). I have modified the original proof of concept Nikolaj produced.
If your interested in the arduino code, I have a GitHub repository with the 4 axis software if anyone wants to build their own.

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I am currently working on a modification to the arm shown above, and have incorporated a 5th axis to give me the ability to reach far more than the 4th axis. In order to implement this additional encoder I have had to completely re-program the arduino from effectively a trig solution to a forward kinematics method. Talk about a HUGE learning curve!

I have some discussions ongoing over at the processing forum as the group there is obviously able to answer some specific questions pertaining to the software platform. I have the arm working off of a Raspberry Pi with a touch screen with the goal of having a wireless platform I can move around the shop or take on the road. So far so good.

Will update on future progress and images of the 5th axis soon as I have hit a bit of a snag. I need to remake a part and my CNC decided to eat a spindle bearing. Should have it up and running in a week(ish) and I can get back to the arm.

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#2

That is extremely cool. I like it a lot!

#3

Very cool. Thanks for sharing.

#4

Wow, nice job! Looking forward to seeing the 5-axis variant too, in progress and complete. :slight_smile:

What do you do to record a point? Do you have a button for your other hand, or foot switch, or is it embedded somehow in the effector?

I can’t count the number of times I’ve thought about — and yet never started — making some sort of CMM, though I was thinking of a cartesian CMM using DRO scales for X/Y/Z because it seemed like it might be more hobbyist-friendly. My idea would be more bulky and less flexible than your elegant arm.

The URL to the discourse forum didn’t work for me; said it didn’t exist or was private. Here’s what I found:

Are you running Processing on the Raspberry Pi or on an attached arduino?

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#5

Michael,
The arduino does the heavy lifting as it were. It reads the encoders and does the forward kinematics math. It then outputs Cartesian X,Y, Z coordinates via serial. The Pi runs processing and takes the coordinates and displays the point in digital 3D space. Right now either a button on the Pi touch screen or keyboard keys can be used to record a point. Once I have the arm finalized I will put a button on the end effector to trigger a point capture. Likely put two or three buttons on it as there is also a feature where you can capture a surface as well as points.

There are a few things that are exciting about the setup in my mind. With the advancement of arduino variants, it would be easy to have the arduino wireless.

Here is the processing forum link again, hopefully it works, it should be public as its just a forum post: https://discourse.processing.org/t/exporting-dxf-is-mirrored-cmm-arm/13995

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