[bcmaint]

We have an old vertical that ran on a dos program. I'm in the process of converting it to KmotionCNC using Kflop/Kanalog to control the servos and VFD spindle.

The servos are Glentek. The drives are Glentek GA377-1. I had contemplated using gecko drives but everything is already there.

Two things are puzzling me....so far.

#1 When I enable the drives, I'm used to the servo's basically locking up. You can't move them by hand. When I enable the drives on this machine, I AM able to move them. The try to return to the original position, but I can move them kind of easily.

#2 After each test, it doesn't always return to the same position. It's always 1-3 counts of on the Axis tab.

Attachment 264438

[TomKerekes]

Hi bcmaint,

When I enable the drives, I'm used to the servo's basically locking up. You can't move them by hand. When I enable the drives on this machine, I AM able to move them. The try to return to the original position, but I can move them kind of easily.

With a low P gain and no I Gain the servo response is likely to be very poor/weak. With a P Gain of 0.5 it will take 2 encoder counts of error to even get 1 DAC count of output drive. It also seems you have a torque amplifier (the green Output plot is proportional more to acceleration than velocity). With a torque amplifier damping (D Gain) is required to be stable with higher P Gains.

After each test, it doesn't always return to the same position. It's always 1-3 counts of on the Axis tab.

Same reason as above.

Regards

[bcmaint]

Thanks Tom,

The only information I have on the Amp is a PDF drawing. The jumper J3 is in place, saying it's in current mode. Not sure if that means anything,

I tried raising the P value, but anything over about 1.5 causes it to become unstable. Should I be raising the D value as well, and in what increments?

[bcmaint]

OK, I think I have my axis figured out. I played with the PID settings and they seem to be stable and rigid now.

Next question is the spindle. I have it set up in KMotionCNC using M3,M4,M5 and S. I can get it to turn on and rotate, but the speed adjust slider isn't working.

[bcmaint]

I zoomed in on the tuning graph. It looks like command and position track right on except for this part.

[TomKerekes]

Hi bcmaint,

In a DC motor torque is proportional to current, and acceleration is proportional to torque (they are all basically the same). Does your motor have a tachometer or any other feedback to the amplifier?

But yes you most likely need D Gain to have high performance. An analogy I often use is a car accelerator pedal. With P Gain only it means you push the pedal down proportionally to how far you are from a Stop sign. Imagine as you approach a Stop sign you reduce the acceleration. This results in still increasing velocity until you fly past the Stop sign (overshoot). This only works at all if the amount you allow to push the gas is limited to a very tiny amount to creep up to the Stop sign. Now consider dragging a heavy sled behind the car. As you approach the Stop sign and reduce the gas to a small amount, the drag force will exceed the engine force, and the car will begin to decelerate before reaching the target. D Gain is like adding a Drag Sled behind the car. The higher the D gain the more the drag. The more D Gain you have (drag) the more P Gain (gas) you should be able to use.

Try adding D gain. Every system is different. Try starting with a value of 1 and repeatedly increase by ~ 50% until you see an effect. Too much D gain will cause the system to also go unstable.

HTH
Regards

[bcmaint]

Thanks Tom,

There is no feedback to the amplifier.

[bcmaint]

OK, I tried using the 4 C programs to control my spindle since I couldn't get the speed slider to work using just output bits/DAC. The bits turn on and the console states "jogging spindle 16666.66667 counts/sec" but I have no analog signal and no spindle movement.

This is my MySpindleDefs.h file:

#define SPINDLEAXIS 2 // Axis Channel to Jog to rotate Spindle
#define FACTOR (1000/60.0) // to convert RPM to counts/sec (counts/rev / 60.0sec)
#define SPINDLECW_BIT 144 // bit to activate to cause CW rotation
#define SPINDLECCW_BIT 145 // bit to activate to cause CCW rotation
#define SPEEDVAR 99 // global persistant variable to store latest speed
#define STATEVAR 98 // global persistant variable to store latest state (-1=CCW,0=off,1=CW)
#define KMVAR PC_COMM_CSS_S // variable KMotionCNC will pass speed parameter (113)

I have the VFD wired to DAC 2

[TomKerekes]

Hi bcmaint,

Before attempting to modify C programs or configuring KMotionCNC first make sure you have configured a KFLOP Axis to control the spindle speed. Test it using KMotion.exe Console Jog Command as described here:

KMotionCNC Spindle Control

Regards

[bcmaint]

Tom,

I can get the axis to move fine following those instructions. The problem comes when I try to run it in KMotionCNC using the c programs in the CSS folder. I modified it to use axis 2 and bits 144 and 145. The bits turn on and off, but I'm not getting any 0-10v analog output.

[TomKerekes]

H bcmaint,

How did you configure KMotionCNC | Tool Setup | S ? Is it using Var 113?

Regards

[bcmaint]

Yes, the only things I changed are the axis channel and cw/ccw bits

[bcmaint]

Followup: after going through the setup instructions, I went back and tried using the output bits and DAC selections in KMotionCNC but with the values from the other part, ie -2.047 and -2047 and sudden;y I have movement. I'll need to adjust it some since we'd never run it at full 10v speed. Making progress and thanks again for all the help Tom.

[bcmaint]

The most we would want would be DAC2=-500. Would I set the minimum to -500 and would the scale stay at -2.047?

[TomKerekes]

Hi bcmaint,

Do you intend to require CSS? If so you would probably be better with the C Program approach.

Correct setting the min to -500 will limit the DAC to 500 counts (~ 2.44V).

Not sure where you get the -2.047 Scale from. You will need to adjust the magnitude (keeping it negative) to get the actual RPM to match the specified S value.

Regards

[bcmaint]

We don't plan on using CSS. I got the Scale the Basic Configuration here:

KMotionCNC Spindle Control

[TomKerekes]

Hi bcmaint,

The -2.047 Scale was an example for a system that ran 1000RPM with a 10V input. Most likely you will need to find a factor that applies to your system.

Regards

[bcmaint]

Finally back on the project. One of our axis has a little bit of backlash. I see in the configuration screen backlash mode can be turned on. What kind of values should be in Amount and Rate? Are these actual linear values, ie .001 or are they counts? And I'm not sure what Rate is.

Thanks

EDIT: Nevermind, I found it on the website and answered my own question.

[TomKerekes]

Hi bcmaint,

btw you don't need to go to the website to look these things up. With two mouse clicks you can get to an explanation of any parameter on any screen. Click "Help" and then the parameter.

Regards and good luck with your backlash.

[bcmaint]

I ran into a snag yesterday. We're using this on a lathe, x and z axis only. I have x and z on analog out 0 and 1. Analog out 2 is used for spindle speed. I got everything working individually but when I try to move them in KmotionCNC the spindle tries to move when jogging the Z axis. I had everything working a couple weeks ago and didn't change anything. Not sure what's going on now.

I'm using the "Basic 2 Axes" Main Dialog Face.

EDIT: Also I'm doing all of this on a laptop, but will eventually be using a desktop installed in the machine. Is there an easy way to transfer any changes made to the KmotionCNC program or will I have to set it all up manually?