On Tuesday 07 July 2009, Glenn R. Edwards wrote: >Yes, I had a stepper system run backwards when pushed too hard. I believe >it was a combination of accel and start frequency being too aggressive. >However, the backwards motion was NOT smooth or at commanded speed- slow and >noisy is what I remember. Jeffrey did not report, though, that his >backwards motion was anything but normal except direction-wise. So, I'm >thinking this isn't the case here. > I think I'd have to qualify my statement by saying that it would generally only apply to the case of running full step as even half-step would make smooth backwards motion very difficult to do. >Glenn > >-----Original Message----- >From: emc-users-boun...@lists.sourceforge.net >[mailto:emc-users-boun...@lists.sourceforge.net] On Behalf Of Gene Heskett >Sent: Tuesday, July 07, 2009 7:30 AM >To: Enhanced Machine Controller (EMC) >Subject: Re: [Emc-users] Weird EMC2 tuning issue (direction reverses >intermittently) > >On Tuesday 07 July 2009, Andy Pugh wrote: >>2009/7/5 Jeffrey Pease <jpe...@peasej.com>: >>> One mysterious issue I've seen that I'm trying to figure out is that >>> very, very rarely, a movement command to the milling machine will >>> make an axis move the correct distance in the INCORRECT direction. >> >>Is there any possibility that this is a mechanical problem with the >>motors? I am wondering if they can get into some form or resonance when >>pushing the step rate too far, such that they start stepping backwards? >>Note that I don't even know if this is possible/ > >Yes it is, particularly when using a driver that can't microstep. Resonance >can build up to the point where its actually turning backwards due to the >magnetic spring action, and it could find it easier to keep on turning >backwards, having overshot the center. I have not personally observed that >in my machine however, cuz if it skips a step, mine just locks in place and >sings. Dampers will help to squash this, allowing considerably higher >speeds. >The dampers should take the form of loosely coupled weights that can slip >and therefore absorb the resonance motions. Mine are built from a steel >spool with one flange removable and adjustable, with alternating layers of >sheet rubber whose center holes are a drag fit on the spool hub, and large >fender washers that are free to turn on the spool hub. The removable flange >is adjusted so that the stack of washers/rubber is snug but can be turned in >place when the motors are powered up & locked. This works well for >microstepping drivers such as the xylotex I use, allowing about 2x speed >increases but probably needs a more mathematically based design for stuff >running at half or full step. > >They can be see at <http://gene.homelinux.net:85/gene/emc> > >-- >Cheers, Gene >"There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." >-Ed Howdershelt (Author) >The NRA is offering FREE Associate memberships to anyone who wants them. ><https://www.nrahq.org/nrabonus/accept-membership.asp> > >Celebrate Hannibal Day this year. Take an elephant to lunch. > > >---------------------------------------------------------------------------- >-- >Enter the BlackBerry Developer Challenge This is your chance to win up to >$100,000 in prizes! For a limited time, vendors submitting new applications >to BlackBerry App World(TM) will have the opportunity to enter the >BlackBerry Developer Challenge. See full prize details at: >http://p.sf.net/sfu/blackberry >_______________________________________________ >Emc-users mailing list >Emc-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-users > > >---------------------------------------------------------------------------- >-- Enter the BlackBerry Developer Challenge >This is your chance to win up to $100,000 in prizes! For a limited time, >vendors submitting new applications to BlackBerry App World(TM) will have >the opportunity to enter the BlackBerry Developer Challenge. See full prize >details at: http://p.sf.net/sfu/blackberry >_______________________________________________ >Emc-users mailing list >Emc-users@lists.sourceforge.net >https://lists.sourceforge.net/lists/listinfo/emc-users
-- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> The distinction between true and false appears to become increasingly blurred by... the pollution of the language. -- Arne Tiselius ------------------------------------------------------------------------------ Enter the BlackBerry Developer Challenge This is your chance to win up to $100,000 in prizes! For a limited time, vendors submitting new applications to BlackBerry App World(TM) will have the opportunity to enter the BlackBerry Developer Challenge. See full prize details at: http://p.sf.net/sfu/Challenge _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
