Encoder scall, x axis off 1/16 over 8 foot

Is there a mathematical calculation to correct error over 8 foot. I am just stabbing at it trying to get it exact, but measuring with a piece cut with a tape measure. I know thats not accurate but it is the best I have at the moment.

encoder scale is 3967

I suspect a tape measure may well have +-1/16" or greater error at 8 feet
(650 PPM) but you can correct the axis motion (or at least match your tape measure)
by changing the scale to:

3967 * 1+(1/1536) ( motion reads short on tape ) or
3967 * 1-(1/1536) ( motion reads long on tape )
(1536 is 96" *16)

Yeah, I got it close enough.

Thanks,

Bob

This shouldn't be a guess. The number should be calculable from encoder / stepper resolution and the mechanical parameters.

andypugh wrote: This shouldn't be a guess. The number should be calculable from encoder / stepper resolution and the mechanical parameters.

I used came out of the manual for this machine. IT is servo's / rack and pinion, and it was off .y 1/6 over 8 foot.

ITs ok now though. Thanks,