On Sunday 31 March 2019 13:17:59 jrmitchellj wrote: > As I tell the robotics students, design limit switches to survive > missed detection & over travel. > On a milling machine, I would recommend a roller type of switch, that > would come in contact with a cam bar that is long enough to reach end > of travel. > > On my machine, I have two switches positioned about an inch apart, at > the middle of travel. Then the are cam blocks, one positioned near > each end of travel > The roller rides up on the block, trips the switch, and the switch > body is safely out of the travel path. I did my mill this way because > I have sooo many pins available with the Mesa kit. > > On the school mill, I used one switch for each axis, and the cam block > from either end of travel would trip it. > > So no failure (or other malfunction) will crush a switch!
I have my G0704 rigged much like that. But this gantry isn't built like the 704. As an experiment I've about half built when the better half pled hunger about an hour ago, so quit. I have a 4x.7x20 threaded into the front face of the gantry on the right side, whose flat head pushes one of these switches that is mounted on a small bit of pcb glued to the end of a 5/16" x 2" alu cut from some 40 thou panel, but will need to replace that 20mm screw with at least a 30mm and a lock nut. Experimentally it can flex the 2" of alu away from the frame with at least 1/8" of overtravel w/o actually bending it, so I'm thinking an even longer screw to trip it even earlier, and a lock nut so the screw won't work out of adjustment will handle the Y home ok. I think I can rig the X much the same. Z of course doesn't have to move near as far, so a slow search there isn't going to be too much like watching paint dry. But Y might have to move 600mm, so its just got to march right along, ditto for the nearly 400mm X might have to move. Thanks JRM. > > --J. Ray Mitchell Jr. > jrmitche...@gmail.com > > > > "Good enough is the enemy of excellence"author unknown > > On Sun, Mar 31, 2019 at 7:03 AM Gene Heskett <ghesk...@shentel.net> wrote: > > Greetings everybody; > > > > I think I've got the coolant pump starting problem fixed. Ignore > > that faint knocking sound. > > > > Now I would like to use a teeny little pushbutton (6x6x2.5mm tall) > > between two solid parts of this machine for home and potentially as > > limit switches. > > > > However the amount of available overtravel after the switch has > > clicked is quite limited unless this switch is mounted on something > > crushable so that the getting stopped overtravel does not crush the > > switch like a Coors can. > > > > Is there a way to determine how much overtravel vs approach speeds > > is occuring? > > > > I ask because a wide open x or y move can do around 220 ipm on this > > machine, and that stopping distance is not an ignoreable distance > > when the switch only has maybe .010" of overtravel after its > > clicked. > > > > So I first would like to determine the maximum safe SEARCH_VEL I can > > use for homeing, then from that, be able to set MAX and MIN LIMITS > > far enough away from the crash stop to provide crash protection in > > the space between the LIMIT set in the ini file, or how much crush > > room I have to build into the switch mount? > > > > Also, in attempting to minimize this stopping distance, what or how > > can one detect a motor step slip if the ACCEL's are stopping the > > motor faster than it can stop? Hopefully without pounding a $90 dial > > into junk. > > > > Thanks all; > > > > Cheers, Gene Heskett > > -- > > "There are four boxes to be used in defense of liberty: > > soap, ballot, jury, and ammo. Please use in that order." > > -Ed Howdershelt (Author) > > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > > > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
