EMC, INI , MIN_FERROR and acheiving maximum accuracy

Asim

The biggest limitation to accuracy or repeatability is the relatively low encoder counts. When you get serious about making the machine more accurate you should think about new encoders.

Since you are using inch definitions you will not want to reduce ferror or min_ferror very much or you will quickly run into the kinds of errors that you see. You may be able to increase gain (P) some. Until you hear the motors buzzing and then reduce it some. You can also put in some feedforward (ff1). This can probably go as high as 8 or 10 without doing much bad to the setup.

You might start with a battery box. This is simply a supply of at least 10 volts that you connect to the velocity terminals on each axis. I use a variable resistor and a couple of buttons or a double pole double throw switch and a momentary button to send commands to an axis drive. Now you can tune the axis drive to the motor and load that you have. The motor should come up to the speed command and not overshoot much.

From there the tuning of the EMC is not that hard. Write down the ini settings change them a bit and see if the motion is better or worse. I write a little line or square program so I can watch it run after a setting change.

Hope this helps.

Ray

> From: "Asim Khan" <asimtec@...>
>Subject: EMC, INI , MIN_FERROR and acheiving maximum accuracy
>
>hi!
>I've recently runned the spindle of my old gold hurco milling machine
>which now has EMC with STG-II as machine controller.
>I just now have made my spindle running. and i have cut some
>circles cut on a wooden log. now I want to super tune my EMC system
>so that i can have maximum possible machine resolution available.
>
>Here are some of my machine settings:
>
>MACHINE resolution = 0.03 mm or 0.001 inch (as depicted in machine'
>smanual)
>Encoder resolution = 200 (lines) x 4 = 800 counts per revolution
>
>lead screws of my machine take 5 revolution for 1 inch
>
>therefore i have in my ini the setting of INPUT_SCALE parameter
>to 4000. (INPUT_SCALE)
>MIN_FERROR value in my ini is 0.01
>
>I want to know what minimum value i can set for MIN_FERROR ?
>so that my machine gives maximum accuracy
>i've observerd that decreasing the MIN_FERROR severely affects
>the tuning of beds and causes all time famous and bad "following
>errors".
>
>Please put some light over super tuning of machine for acheivement
>of maximum possible accuracies. What are the things that limit it
>and what things must be done to get an EMC based system running
>at maximum possible accuracy
>
>I had posted the same question before on the same forum, hoping that
>jon elson, paul, ray henry and les watts may find some time
>replying my post!!
>
>warm Regards
>@sim