K2 Retrofit with pico systems servo amplifier and encoders using 7i95t

Hey guys I have been having a hell of a time trying to get closed loop pid tuning going, which i've done before pretty easily.The Z Axis seems to require over 500 P in order to have proper cmd-pos and fb-pos being in line or on target.No matter what I do I seem to get this crazy drift once im done pressing the job button.Maybe someone can help out?I have tried tuning to no end. The Z Axis has a shock which creates resistance from it falling downwards.Maybe my scale is incorrect or something else?The Servo Amplifiers use Digital PWM/DIR

   

"The Z Axis has a shock which creates resistance from it falling downwards."

If you remove the shock, what happens?

Does it fall under its own weight?

Is there any way you can make the Z-axis lighter?

(By removing superfluous stuff to reduce weight)

Perhaps you need a beefier motor on the Z-axis.

The machine worked before, but basically your saying due to the amount of power being used aka the P needed to get the motor to move and then the drift is evidence that the motor is probably a little under powered? So maybe I need to redo the tuning overall instead start from P = 300, D = 0, I = 0, BIAS = 0 FF0 = 0 FF1 = 0 and FF1 = 0 and see if im still getting drift? The other option is to see if i can increase the servo-thread update frequency? from 1000000 to 900000? That would get more more cycles per P right giving me more response, but is essentially the same as increasing right?

Ignore what Langdon suggests, his advice is unreliable at best, mostly uninformed and most formed in an empty head and produced rectally.
My apologies for sourcing the thread and being so crass but many a time I have seen the above mentioned member not answer the topic and speak non sense.

Whilst I myself don't have correct answer Tommy or some other more knowledgeable member may chime in.

As for decreasing the thread period, aka increasing thread frequency I would run a latency test using the new figures the see how this affects latency, just to be sure there are no surprises, the Linuxcnc docs will have this information, but it will be need to run from the command line.

Once again apologies for the crass warning.

If these are voltage mode (bare PWM) drivers, the tuning is somewhat like
velocity mode servos (with low velocity loop gain) That means that FF1 is critical.

I would first set a relatively  low P term and adjust FF1 so that during constant velocity
the motor neither lags nor leads the desired position (too much FF1 will make the
position lead and too little will make it lag) Note that this is just for tuning during constant
speed motion.

Next I would adjust D as high as possible while remaining stable.

Next do the same with P and back off about 30% from where it becomes unstable

You can now add some FF2 to compensate for the following error during acceleration
and decceleration.

Finally you can add as much I term as is stable (watch out for big oscillations)
and then back off about 50% from the point where it became unstable

Note: If you need to retune FF1 , you need a low P term and zero  I term

Also if you can decrease the Ethernet latency and run a higher frequency servo
thread, the performance will be improved.

these are PWM digital signal, pico systems servo amplifiers, as far as im told the pwm from the 7i95t is digital. Well not so much as im told but also through experience, heh pwm analog didn't work dont ask how i know i dont want to know how i even know. Just call it a misunderstanding in hardware specifications.