I’m in the planning phase of my sandtable build and would like some feedback about if some things are possible the way I imagine them. First to the construction, I’m going to build a polar table similar to the sisyphus tables, I also want to be able to use 2 balls and a parking feature for 1 of the balls. The balls always move on opposite sides, if one is at the center the other is outside and vice versa. I hope you can understand what i mean
Since I couldn’t find any firmware specific for this kind of polar kinematics I will use marlin configured for a regular cartesian machine, but set it up so that Y 1 equals a half rotation (1 radian). Software endstops will be disabled to allow it to move infinitely in both directions.
I can then use a simple script to convert .thr files to gcode, starting the gcode with G92 Y0 and G91 makes this straight forward, since everything moves in relative coordinates I don’t have to worry about converting the crossing from 360 degrees to 0 degrees correctly. As I understand it the Thetha values in .thr files are also relative, but the Rho values are absolute? Still shouldn’t be an issue, since I can just use the delta between coordinates for the Rho value.
For the parking mechanism I will use some sort of hook shape that moves in and out with the Z axis motor. This way it doesn’t interfere with the drawing surface. Before parking/unparking the machine would need to be homed.
Everything gets controlled by a raspberry pi with octoprint. What I’m not sure about yet is if it is possible to also run NodeRed on the same pi to host a simple web interface to control an RGB led strip… Or if it’s somehow possible to enforce the rule that only patterns with the same starting Rho as the ending Rho of the last pattern can be selected.
Sorry if this is a bit all over the place, I have too much stuff that I’m thinking about at the same time
I’m gratefull for any feedback