Messages

1

General Mach Discussion / Re: Problems with AC Servos

« on: May 21, 2013, 05:58:21 PM »

Will definately check that when we get the new ballscrews, Mike!

Thanks

2

General Mach Discussion / Re: Problems with AC Servos

« on: May 18, 2013, 11:46:32 AM »

OK, feel even stupider now. It isn't even a 1605 ballscrew, it is a 1610 ballscrew with dual threads. Didn't even know those existed! Didn't notice the steeper slope when measuring.

It was pretty easy to see when we got a permanent marker and run it through the threads.

Going to get smaller pitch ballscrews now and that should fix things!

3

General Mach Discussion / Re: Problems with AC Servos

« on: May 18, 2013, 10:56:14 AM »

Thanks for the answer, Hood. We just discovered we can't wrap our heads around!

I can't believe we haven't noticed this before, but when you spin the ballscrew one revolution it goes 10mm! And we are using a ballscrew with a leadpitch of 5mm. Feeling pretty stupid now, but how can this be? Must be thinking wrong somehow.

So the driver was doing 1:1 steps, after all.

4

General Mach Discussion / Problems with AC Servos

« on: May 17, 2013, 02:17:01 PM »

Hello!

We just bough 3 sets of these drivers+AC servos.

http://www.artisantg.com/info/Oriental_Motor_VextaKXP_Manual.PDF

We have been having some accuracy issues with them.

It says 400steps/rev, so with our 1605 ballscrews it should be 400/5=80 steps per mm, but in order for it to scale properly we have to put 40 steps per mm in motor tuning.

It seems like either the motors react to both the falling steps and the rising steps? Or that we get some kind of double pulsing.

When we cut, holes also become a bit square. Engraving is pretty ugly, especially where the engraving changes direction. It seems a bit 'wiggly'. The motion of the motors can sometimes look a bit sluggish.

The motors also sometimes makes these short 'groaning' noises, when standing still. Is this normal with servos?

Pretty sure it's not the mechanics, as it worked with steppers before.

Could it have anything to do with interference? Seems strange because the errors always seem to occur on the same spot. Even if we rescale things, the errors are the same size.

Any help would be appreciated!