PID TUNING FF1

HI..
i have question for pi tuning
i am using ethercat servo with linuxcnc
recently i retrofit moriseiki sl6 machine

i found strange issue during installation

z axis motor setting in ini file if i set FF 1 = 0

my z axis motor show 100 % load during 10 to 100 rmp (i measured load on ethercat bus (actual torque))

and above 100 rmp it show around 30% load that is acceptable

now i make some trial and set FF1 = 2

then i find load between 10 to 100 rpm is 30%

but z axis work like very high power

i think this FF1 is add some command to servo command

but now i want to reduce hunting when i move with handwheel z axis move is strange
but position accuracy is ok if i move 0.1mm with handwheel it move with hunting

x axis move normally with ff1=0 value

may be this is mechanical issue but ff1 effect i am not able to understand

can anyone explain what exact ff1 does with command

for information i can tell that this machine works since last one year without any issue

nut i always get complains from that machine operator that x axis move very smoothly and z axis move is very strange

may it damage mechanical parts in ball screw

A properly tuned and configured servo should never reach 100% output under normal conditions.

Ordinarily, a velocity mode servo in Linuxcnc will work best with an FF1 near 1 (if inputs are scaled right).

Jog wheel inputs are incremental, and can result in jerky movement. But there are ways to smooth them out.

You may need to share your config files for us to make better recommendations. Also images of halscope traces of following (or PID) error, velocity command, velocity feedback and PID output would make giving suggestions for servo tuning easier.

thanks
i will arrange all information and post soon