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.
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.
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.