Another servo tuning

now I did 5 runs 0 to -390 and the results are attached.
 

Tommy it is about to happen. (the explosion)
I did about 20 runs 0 -390 and the dial indicator moved about 0.01mm
how is this possible steps in one dir - steps in other dir should equal to the 0 on dial indicator shouldn't it? in open loop setup. if there was play backlash or so it would not increase steady in one direction.

so what the? What am I missing guys? what am I doing wrong?

well I left it in velocity control didn't I so I guess this slight overshoot could be expected. I am guessing

I am just waiting for something to happen since i can not help as i never used EXE anything, well except stuff i have come to utterly hate = the exe files in windows!

myval wrote:

well I left it in velocity control didn't I so I guess this slight overshoot could be expected. I am guessing

In that case it is working incredibly well!

There are a number of ways to configure this, and what you accidentally have might be a good one. 

ie, servo drive in position mode, stepgen in velocity mode, PID active but with P=1000 and FF1 = 1. Then the PID takes stepgen-pos-fb as the feedback. (This is the usual setup for a Mesa stepgen config, as the PID allows for better performance as the theead period varies) 

Alternatively you can put the stepgen in position mode and completely ignore the PID. motor-pos-cmd => stepgen.position-cmd 

In either case you can continue to feed the _joint_ pos-fb from the encoders, and that will give you an accurate f-error reading. 
 

I set it in position control without pid , motor-pos-cmd => stepgen.position-cmd 
just get this massive ferror spike but it runs ok. Hits dial indicator within about 0.01 which is fairly decent I guess would only like to bump it up when I run highspeed grinder spindle on it but that is not current issue.
This acceleration and speed is as good as the machine can go, well can go slightly faster but I don't think there is a need for more speed.

So where do I take it from here?
Why is the ferror so spiky?
How to get rid of that massive spike at the start?