On Wednesday 23 January 2013 21:02:47 Stephen Dubovsky did opine: Message additions Copyright Wednesday 23 January 2013 by Gene Heskett
> Gene, > Nowhere does it specify in the graphic that the two HAVE to be separate. > The drawing is arbitrary/universal and just showing which edges are used > on which steps. If you set the SEARCH_VEL reasonably high enough the > machine must over travel the switch due to deceleration. Have you > tried setting your search velocity high enough that the over travel is > greater than your backlash compensation? > > Stephen No I haven't Stephan, because its backed up against the end of the workpiece in the chuck in normal use, is a solid black of alu with a sheet of double sided pcb materiel glued to the right face for the contact. If I hit it that hard and fast I would be crushing the pcb material. So my initial search is at about 2"/min, with a final search vel of about .2/minute. Repeatability is someplace in the 4th digit to the right of the decimal point even with 23 thou of backlash. So we aren't talking about a switch at all, but a contact with hysteresis of perhaps .0001" max. That backlash is going away, I now have a 16mmx5mmx675mm ball screw laying on a chair cushion and am milling the rest of the parts to install it as I sit here yakking. And wonder of wonders, we actually have enough snow to turn the ground white! We are about 40" of rain or equ behind since last spring. > On Wed, Jan 23, 2013 at 4:11 PM, Gene Heskett <ghesk...@wdtv.com> wrote: > > On Wednesday 23 January 2013 15:59:55 Bruce Klawiter did opine: > > Message additions Copyright Wednesday 23 January 2013 by Gene Heskett > > > > > I am curious, how does LinuxCNC back off of a limit switch? > > > I have a bridgeport with hand wheels so it is easy for me, just > > > wondering how this is done on the big machines. > > > > > > Bruce > > > > As shown in the gfx on the wiki under homing, there is an implicit > > assumption that it is a mechanical switch, with a bit of hysteresis > > space between the close and the open going the other way. It's > > fairly well explained, but the lack of hysteresis in an electrical > > contact such as I am using, means I cannot set my backlashes for > > total compensations, because the backlash takeup move may reopen the > > contact, and its a show stopper error if the switch is already open > > when the backup move starts. I have x home working about 90% of the > > time by setting backlash to half a thou in the .ini file for x on my > > lathe, and around 3 thou less than real on my old sloppy z. When x > > works, it does all the motions in just a few milliseconds once the > > initial contact has been made. The old Z was the same except for the > > 300 milliseconds the backlash moves of 20 thou take. > > ------------------------------------------------------------------------ > ------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, > CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills > current with LearnDevNow - 3,200 step-by-step video tutorials by > Microsoft MVPs and experts. ON SALE this month only -- learn more at: > http://p.sf.net/sfu/learnnow-d2d > _______________________________________________ > 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> Onward through the fog. I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Master Visual Studio, SharePoint, SQL, ASP.NET, C# 2012, HTML5, CSS, MVC, Windows 8 Apps, JavaScript and much more. Keep your skills current with LearnDevNow - 3,200 step-by-step video tutorials by Microsoft MVPs and experts. ON SALE this month only -- learn more at: http://p.sf.net/sfu/learnnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
