Sled will not go to top of board same parts are cut different sizes

Hi Jimr,
I reviewed your last posts on this topic as well as the Holey Calibration Topic.

This is the kind of situation where we have a chance to share about what is going on in the arduino, and name new places to recognize the situation.

For the context, here is what makes the arduino complain about not finding positions error:
The arduino keeps in memory the amount of chain that is extended above the sprocket 12 O Clock position. At power up, it reloads the last values saved in the EEPROM.

At first, the arduino has to figure out where the sled is on the workspace, the arduino will use these chain length values along with some parameters describing your setup as entered via GroundControl.

The arduino always limit sled movement to not exceed the workspace coordinates in knows. And when figuring out the sled, it will always assume the sled has to be on the workspace. If it can’t figure out how these chain lengths make up a sled position on the workspace, it will flag this “can’t find position error”.

Now why would the sled not be on the workspace anymore (especially because you see it is)? Usually because it is somewhat close to the edge before some parameter change. (remember that the workspace boundaries you see and the workspace boundaries arduino estimates are different until calibration is fine). So when changing parameter, you want to first bring the sled close to the center. Otherwise, after a change it might end up for the arduino to see it outside, even maybe just a little bit.

Actually, the arduino will try to figure out sled position after each related parameter change, or at power up. If you get into the “can’t find position” it won’t want to move. But you can revert parameters, (click stop button in upper-right GC will show x,y recomputation results), then be able to command it to move the sled, then enter parameters again. No need to go through the burden of reseting chain lengths. These should always be fine unless you get chain skip or off the sprockets.

I have also met this situation when I had mistakenly input a related wrong parameter value in GroundControl ( a typo). Say… a number out of range like 35012 mm motor distance.

So…
To help you, I need to understand the details of your current setup and you recent actions.
Could you share the GroundControl.ini file listing all you setup parameters?