Jack Ensor wrote:
> Jon Elson wrote:
>>If you make 
>>several 1" moves in the same direction with incremental jog, 
>>what is the error?  
>>
> 
> Zero, ignoring backlash when giving it individual G1 or G0 commands.
The rest of your data is hard to interpret.  I think the most 
important piece is this one, that the error only happens when 
the direction changes!  That has to mean something.  With 
step/direction drives, the most common error is from the 
direction signal changing too soon, while the steps are still 
being generated by the drive.  That can't be the case here, as I 
understand it.

I would suggest you slow down the acceleration markedly, and see 
if the problem changes.  I also note that the X problem doesn't 
seem that bad, and could be partially attributed to the 
machine's actual position landing somewhere within the backlash 
bound.  The Y axis is so much worse that I have to start looking 
at hardware.  Why should the Y axis be showing so much more 
change in position than X?  The software driving the axes are 
the same.  Maybe you have a bad transistor, bad motor, loose 
pulley or coupling, etc.

But, what I was getting at above was if the error only shows up 
on direction reversals, then maybe the "bump" that happens when 
the backlash is taken up causes the motor to jump a few 
multiples of 4 full steps.  Slower acceleration would allow the 
motor to still be moving slower when it bumps into the other 
side of the leadscrew/nut.

Jon

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