On Sun, Nov 29, 2009 at 1:51 PM, Jon Elson <[email protected]> wrote:
> Pat Lyons wrote: > > Hello folks, > > > > Hope you had a nice turkey day and all. > > > > I'm trying to understand why my Y axis following error is so much worse > that > > my x and z. I gave them all equal efforts regarding the tuning process, > but > > Y seems to be much more finicky a mechanical response- oscillations > appear > > to be a serious issue- I can get it down to about a thou of following > error > > at constant velocity but the initial lack of acceleration causes a spike > in > > f-error at the beginning of each move... > > I've tried toying with FF1 and FF2 as instructed by several of you, but i > > found that if i deviate from the values I've found, the response goes > nuts > > with skyrocketing f-error. > > > You might need to tell us more about the machine, especially if a > mechanical > aspect of the problem is suspected. > > What servo amplifiers are you using, what controller board? The servo drivers are shown here: http://www.cnczone.com/forums/showthread.php?t=92599 and though they are labeled as EG&G torque systems, they pinout like Westamp drives. (Driven by a 7i33 and 5i20) > Using > Halscope, > you can measure the frequency of the oscillation. If it is 500 Hz, that > is half > of the default servo frequency. If it is in the 10 - 40 Hz range, that > is typical > mechanical resonance. If it is a couple Hz, that is typical tuning > instability. > Yea, I'd say it falls into the <15Hz category. I was thinking about finding a way to dampen the Table's mechanical response by using the gibbs (I'm not sure thats the right name for em, but im reffering to the screws that are used to apply pressure to the dovetails on the ways) > > FF1 and expecially FF2 are used in incredibly small amounts, typically > 2 -5 for FF1 and as little as .0002 for FF2. It is VERY easy to overdo > these. > > Jon > Funny you mention FF2 as 0.0002, because i think the highest I have mine (Xaxis) is like 0.0005. My FF values in all instances are below 1. I managed to get it to settle a little with the error, but the biggest trouble seems to be the initial error, which spikes- I would slowly increase D and would end up with much resonance as a result... I was thinking, this could also be due to an improper backlash measurement I've made (i suspect this because the worst spikes occur when changing direction... Thanks a lot for your help Jon, it is very much appreciated, and I hope i get to return the favor someday! -Pat ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
