Greetings all; Thinking on probing on this new machine.
Generally, the workpiece will be fastened to a spoilboard so that a drill thru cuts into it rather than the slotted alu bed. This I'd assume can be thought of as an insulator as a sheet of plywood seems ideal, and if a more precise z reference is needed, it seems 10 thou can be skimmed of the top in an hour or so. It would still be an insulator, meaning the workpiece an be connected to the probe input for GP probing. I've been useing a probe made from a needle threader, but with the fine wire reformed into a sharper V, an have the spindle turning 100-400 rpms, the wire loop then forming a cone, with a .1 uf capacitor that is discharged if the loop touches at any point in its rotation, and being slow to recharge, will hold that logic zero for long enough to register at LCNC's probe input. My question then is, is there enough continuity up the motor shaft and thru the bearings that it can serve as the ground? Or, because the motor has ceramic bearings its shaft is not grounded and I'll have to rig a brush against the side of the probe itself (it has a brass tubing shank of 1/8" OD) to assure a good grounding of the probes tip) This has worked well, with a repeat accuracy well under a thou on the little HF. Or should I figure on grounding the workpiece, and making a probe out of a piece of 14 gauge wire, drilled into a round teflon rod that is in turn chucked in the er-11, and the hot probe is a brush contacting the wire, again with the holding capacitor to store the first fleeting contact long enough to be seen by LCNC. I've done it this way too, and have found the center of a drilled hole to a repeat error well under a thousandth on the g0704. Now, to explore some what if's: If the spinning diameter was known, it could work in 3d, and assuming the size of the hole was known, the distance it travels across the hole could be used to determine that, by probing y-, y+, centering on that, then centering on the x, and a repeat center on the y could give the phantom diameter of the spinning probe by subtracting the travel from the known hole size, which could then be picked up and used to probe the sides of a workpiece, giving data close enough to use the align utilities to orient the co-ords map so it autocorrects for a raw part thats fixed at a small angle. I like that as I've never been able to keep camview working long enough to use it for that on the g0704. I even have the gui stuffs for that already installed in the g0704's axis! Fiddly stuff changing the probe tool in and out, and may change its working diameter if it gets sprung while remounting the probe tool but it could work just fine as you can calibrate that error out. Would any of you have a better idea that doesn't cost $300? IOW, get all the precision needed from the probe itself each time you use it, it recalibrates itself if you know how big the hole is and you are useing the side of the probe. Cone tips would be out because a z diff would modify the results. The possibility of permanently mounting a calibrating hole comes to mind, calibrating against that, then probing the workpiece for alignment. Anybody like? I do. Merry Christmas everybody. 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
