On Sunday 07 July 2013 22:20:01 Eric Keller did opine: > On Sun, Jul 7, 2013 at 4:08 PM, Charles Steinkuehler > > <[email protected]> wrote: > > Is this sort of probing possible with LinuxCNC? > > Didn't we have a discussion in the last year or so about someone that > was probing the surface of a circuit board using LCNC?
That may have been me. I add to the output of pcb2gcode, probeing to establish the jig location which fixes the board location, then probe the surface to establish 0.0000. The idea is to remove enough copper without also removing .005" of glass which isn't too healthy for the bits even if they are carbide. I got tired of the pallet holder not being square and milled it for a ridge on the back that just fits the table slot, so its always square to the table. I can run the drill files .035 thou deep from both sides of the board and they are within .001" or so of perfect, meet in the middle of the boards thickness registration if I pay attention. To establish location xy, I have a small bit of 3/32 diameter brass tubeing set into the pallet .2" to the left of the edge of the cavity the board sits in, also .1" in front of the edge of the board, and a probing bit of 1/8" brass pipe telescoped down to 1/16 ID, and a sewing machine needle threader spring loop soldered into the end of that. I fire up the spindle at about 200 rpms, and have a .1 capacitor on the probe line so that any contact discharges the cap long enough the g38.2 can sense it. The code searches both directions in each axis for contact, then puts that axis at the center, then repeats for the other axis and centers it too, then applies the found offsets to the G56 map and switches the rest of the program to use it. Repeatability is about .0015 or better, usually better. The reason the spindle is running is so that the spring used as a probe is effectively cone shaped and perfectly circular in terms of its contact surface. As long as the tip stays within the confines of the 3/32" tubes mouth, and bends and wobbles the wire does as its spinning are moot. The pallet is melamine, so the probe wire, grounded by the spindle touches the tubing and the pcb surface. Works a treat for the xy, then I switch to the engraving bit and probe again to set the 0.0000 z reference. 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> O'Toole's commentary on Murphy's Law: Murphy was an optimist. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
