I've been working on a SCARA arm prototype and reworking the kinematics in Marlin firmware to support it.
At the moment I've got a working build of Marlin and most of the forward / inverse kinematics solved - there are issues with my design that necessitate a re-design in respect to using physical end-stops. I'm looking to use Hall Effect sensors in place of mechanical switches.
Calibration should be relatively simple. Firmware expects initial cartesian coordinates relating to endstop positions, so that it may deduce the initial angles. From there, cartesian X / Y coordinates are translated into the proper angle rotations for each joint (of which there are only two.)
The additions of the Morgan kinematics added to Marlin by Quentin Harley where instrumental in allowing me to see how best to go about modifying the translations. The Morgan kinematics are very similar to a Delta / Rostock configuration. The kinematics for a single arm are very similar to the Morgan transformations.
I have a lot to learn, and still a lot to sort out. If anyone has questions or is interested in using the firmware I'd love feedback.
Here's a video I made for a friend showing some of the first moves:
I'm re-designing the arm to be much more flexible in terms of calibration and reach. I'll post an update if you are interested. Not complaining, but I've been in a really dark space lately and haven't felt like communicating much. I'll try and post some new shots soon.
I tried printing something the other day and it worked pretty darn amazing without being calibrated at all. You can barely hear it move. The motors I'm using are Sanyo something or other with 400 steps per revolution and a Printrboard limited to 16x micro stepping. I'm using a belt reduction to drive the arms but I can't recall the ratio right now. Sorry I'm being so vague. I'll respond soon. I wanted to say thanks for asking though.
... my experience with scara style mechanics shows, that a serial scara lacks of stability and resolution, while a parallel scara is much more rigid and superior in accuracy across the complete building area ... and much simpler to assemble too