Firmware/Software sanity check

Check out this post where I worked some of this out to run a theta rho table with a marlin controller:

There is the caveat that Marlin has no idea you are dragging an arm. It thinks the numbers mean mm. So the feedrates will be a bit goofy, slowing down near the center and whipping around the outside edge.

The thetas are locally relative. So if you need to go from 355 to 365, that is different than going from 365 to 5. In between patterns, you need to reset the theta zero. Rho is always absolute, always zero to one in a thr file. No matter what size the table is.

For endstops, there are optical endstops that don’t restrict movement. Those would be good for the theta motor. The rhoish motor could probably use a regular microswitch, but an optical one could work too. Or maybe even sensorless homing. For the Z/ball deploy, what about using a servo? That would have a built in position and you can set it with M280 S0 or M280 S200. You can easily adjust it and Marlin won’t get confused and think there is a Z axis. I think Z would be fine too, but just a bit more complicated than it needs to be.

As for the second ball. You’ve definitely made a challenge there. Hopefully you have an idea of how to do the mechanics so the extra ball is driven by the same motors and you have some idea of how to deconflict at the center.

Also take a look at the sandypi software. It needs some more developers/users, but it seems like a great start for what you (and we all) want. I haven’t set it uo yet (my table is in progress, indefinitely, but I am trying to win a sisyphus table by vote (the tasting flight one is very close, so help is appreciated, you can vote every day for 1 more week). But I do plan on setting that up eventually and making some PRs to try to help it out.

This sounds like a super fun project. You’re in good company here. Please update us as much as you can. :slight_smile:

1 Like