My table has a pretty consistent distortion occurring directly in the center where the armature I guess has to flip around to keep the ball moving. It's particularly visible where straight lines go through the center, but is visible essentially any time anything passes though it. This error occurs at all speeds, but I typically run my table at the very slowest rate. The picture attached shows it at its lowest speed.
I found a previous forum post: https://sisyphus-industries.com/community/community-tracks/ball-doesnt-go-straight-line-around-center/#post-1238 , where Bruce suggested we could use the table's advanced settings to adjust the "homing offset" but I wonder if there may have been changes to the menu in the two years since that post was made as I don't see any homing offset (unless the "jog" options are what I'm looking for?) and the settings I've tried don't appear to make any difference when I adjust them.
Help! Any info would be greatly appreciated.
You are correct on all counts - the distortion is due to the ball's home position not being exactly dead centered. When the mag-arm rotates with the magnet at true center, there is no visible ball movement. Make sure that the distortion you're seeing happens even after a reboot (which causes the ball to go home, using sensors). If it is OK after reboot, but happens more and more as your Sis runs, this suggests position creep (lost steps, usually due to running at top speed). But if it is consistent, then try to calibrate the home position to true center via the following procedure:
First, make sure your firmware is up to date (several improvements to making homing more accurate have evolved over time).
- Reboot, and after the ball has homed (stopped moving at the center), pause your Sis (if it is starting a track automatically).
- Go to Settings / Advanced / Advanced Movement and use either the Left or Right button to continuously drive the ball around the center. If it is at the center exactly, you won't see any motion. If it moves in a tiny circle, estimate how far off it is (the radius of the circle it makes, using the center of the tiny circle to the center of the ball).
- Jog the ball using the IN button toward the center. If it goes the wrong way, then your home position error is negative (it is past true center).
- Go to Settings / Advanced and then tap the "Advanced" banner at the top 7 times. This expands the menu with expert / diagnostics options.
- Once the menu expands, scroll down to Sisyphus Settings. There you will find "Homing Offset" (under "Jimmy Homing"). Use the slider to enter the distance you estimated (note the distance should be quite small (+ / - 1/8" at most). Hit save at the bottom of the menu and it will reboot. If the center distortion becomes worse, then repeat the above, but chose the opposite direction for the offset.
The procedure is a bit tedious, but you should be able to nail it so that you see NO center distortion. If you can't get it to disappear, it's possible that your mag-arm screws are not tight and the arm is not perfectly straight (which makes it impossible for the ball to be positioned perfectly at the center). That's easy to fix by pulling the bot out, aligning, and re-tightening.
Please let me know how it goes!
I used sandify to put together a real simple small track to speed up the process, it's a lot better now (see image), but still a little offset at maximum homing offset (0.12 inches) so I guess I will have to drop the bot and try to re-adjust it manually.
Thank you for your very thorough help!
We had our weekly support meeting, and this came up. Everyone agreed (including me) that my "procedure" could be made a whole lot easier! I assume you used Sandify to create a track that is simply a line that passes through the center? In the meeting we agreed to create a tool in our app to make this easier (akin to the calibrate tool for RGBW lighting).
I assume you used Sandify to create a track that is simply a line that passes through the center?
Correct, just a short line that passes across the center repeatedly. I've attached it. I'll probably wait until the weekend to drop the bot from the table, I need to do some dusting anyway.
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