Here’s a great actual-delta-bot drawing robot project from Jarkman!

Drawing Delta Robot, made with Anton as part of Dorkbot Bristol’s Draw project.

It’s all Anton’s fault, really. He suggested a delta robot, we built a quick lashup to see how it worked, and the lashup became permanent. Here’s the lashup, built with gluegun and things we had lying around.

Servos are regular 7 quid Futabas, from the very helpful Mad On Models in Newport, along with servo arms, balljoints, and rod with M2 threaded ends. Well, they come threaded on one end, you need to get an M2 tap and thread the other end yourself.

Initial inspiration was from this sweet little delta by mjcbruin. Maths and geometry code (which built on Arduino with no change) to convert XYZ to servo angles came from this marvellous post by mzavatsky. A point to note – the constants for the machine base and effector dimensions in there (e and f) are the sides of the triangles that comprise the base and effector, not the center->pivot distances! Multiply the radius by 3.466, 2/tan(30) to get the side length.

The overall stiffness of the thing is sensitive to the stiffness of the servo arms and servo mounts. We went from plastic extra-long servo arms to all-metal servo arms, and I expect we’ll go to home-made extended arms.

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