Mori MVJR Build Log

I still suggest that you normalize the PID numbers by setting both PWM scale and MAX OUTPUT to machine units/sec at 1825 RPM.

I must be missing something then because when I set

OUTPUT_SCALE to 11.81 = (pitch*RPM/60) = (0.3937*1800/60)
and
pwmgen = 1

The motor speed can't be adjust by the pot to 1800, it can only get up to about 600 RPM.

Maybe I'm not looking at the pwmgen value properly, I thought it has a range from 0-1.

Should I be setting pwmgen to some number higher than 1?

You should not have adjusted the pot (it was right before = ~1800 RPM at full scale)

And yes the range of the PWM generator is +- OUTPUT_SCALE

You should set OUTPUT_SCALE and MAX_OUTPUT to 11.81 (11.81 Inches per second)
now when you set the PWM value to 11.81 you should get 1800 RPM (and 11.81 Inches per second linear motion)

This is what I mean by normalizing the PID, when set up this way, the PID loops outputs values directly in inches per second

OK thanks a million that was what I had wrong, I thought the pwmgen range was -1 to +1.

Welcome.

The -1 to 1 is just the default range...

Progress report, I was able to home all the axis and start tuning PID on the X axis.

I made a program as suggested that moves the axis from 0 to 1 and back to zero.

So far I have improved to the point that I have the PID display gain so the scale read 50um and the graphed curve is about 2-3 graduations. Not sure what good enough is yet and if this relates to follow error or something else.

It seems like the machine moves with less acceleration than it did before, as it seems much less violent than it used to be when it was in 100% rapid.

I also notice that the DRO doesn't make it to 1.000, more lie about 0.720, not sure if that is the DRO lagging or if the machine is falling behind.

I have the following setting in INI
MAX_VELOCITY = 9.833 (this equals the max specified in the manual.)
MAX_ACCELERATION = 20

I looked in the manuals for the CNC and didn't find any indication of an acceleration spec.

Is there a best practice for determining the proper MAX_ACCELERATION ?

"So far I have improved to the point that I have the PID display gain so the scale read 50um and the graphed curve is about 2-3 graduations. Not sure what good enough is yet and if this relates to follow error or something else."

HALScope displays what you tell it to, Are you selecting FERROR on the selected axis in HALScope?

FERROR _is_ the following error

Unless you are plotting FERROR I cannot tell whether the machine is anywhere near tuned (the DRO difference could be that you have a long long way to go tuning)

I was tracking pid error.

I don't know if PID error is an indication of following error.

FERROR _is_ the following error

Thanks, I'll start tracking that too then.

You could try increasing the acceleration until things go wrong...

I wonder what the symptom of too much or too little acceleration would be.

"I wonder what the symptom of too much or too little acceleration would be."

Too much would cause too large of a following error during acceleration.

Too little will make the machine slow on small details

There is also an unseen factor here, the actual torque needed for cutting and perhaps more table load, that is if you adjust your max acceleration to the point that the machine is just able to follow with no load, this means all the drives torque is used for accelerating the bare machine at maximum acceleration and none is left for cutting and table loads

It would be nice to know what the original machine spec was. but lacking that, you could bump up the acceleration until you get large following errors and then back of by perhaps 30 to 50%

Note that setting acceleration up to the point that your drives cant follow is liable to test the drives and machine rather severely so be careful!

BTW I would not mess with this until all the other tuning details are worked out