Center positions (0,0) vs extended chain

Took me some time to realize that the chain that is extended during a calibration is not the same as the centered (0,0) position. What kept frustrating me was that I had marked the chain at position 0,0 (not the extended length), and was trying to follow posts on how to re-center w/o going through the entire calibration, but it always dropped several inches when I told it to go to center. Finally realized that it’s apparently not at 0,0 when extended at the end of calibration.

So what’s the difference between the extended chain length and the length to center (0,0), and which is reflected in the chainextendlength in the ini file? Thanks.

Chainextendlenght in the .ini and in GC advanced settings is the amount that the chain feeds out to connect your sled after calibration. Correct, the link to mark is the one after the feedout and not X0/Y0.

For a 10 ft motor distance something around ~1651mm and for a 12ft ~2032. It does not match with 0/0 as the motor height is not calculated in at this point.

Thanks Gero, good to know! I’ve been trying to calibrate mine off-and-one for many months now, and never able to get it quite right. Thought I’d try just measuring and entering the values directly, after having gained a better understanding of some of the parameters. I’ll make sure to measure/mark the extended length then.

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I think that what you did (marking the chains forthe 0,0 location), but you
missed one step

you need to change the chain length (it’s in one of the settings menues, or you
can edit the groundcontrol.ini file). Just make it so that the value is a
multiple of 6.35mm, even if that means it’s just a little off from the exact 0,0

there’s nothing magic about the original 1650mm lengths (and the more correct
1651 value is just making it a precise multiple without requiring the chains be
re-marked). Having this value position the sled at or near the center would be
an improvement IMHO

David Lang