Greetings all; I have now managed to wreck 3 or 4 half completed attempts at this board by typu's in my code driving the tapered hole probe too far, so I have turned to the contact probes construction.
1. Assume the spindle carrying the ground is turning 2-400 rpms so that any runnout is canceled as the probes end shape is then a cone shaped envelope described by the probe as it turns, and its turning fast enough that the probing motion has only advanced by maybe 0.0001" or less in the time it takes to complete a revolution. 2. The response to a true from the probe is at worst the servo threads lag to get the stopping initiated. So I do 2 probes, one at say 4ipm, back up a bit, 0.010 maybe, and redo it at say .2 ipm for a final G38.2 snapshot capture in $5361-5369. 3. The current involved is a TTL pulldown, maybe 3 mills max, so electrical erosion of the contact isn't a short term problem. This is I suspect true even if a add a small capacitor across the contact to stretch a momentary contact out long enough for reliable first contact detection. 4. What would be wrong with taking the approach of making the probe contact so flimsy it cannot damage the board even if driven sideways out of the hole in the pcb and across the copper while it is still spinning? Rummaging around in the missus's sewing stuff last night, looking for a suitable flimsy straight pin to cabbage, I came across a couple of her needle threaders, those ultra teeny little springs bent in a V that you stick thru the eye of a needle, run the thread through the loop of the V sticking out, and pull this wire, and the thread, back through the eye of the needle thereby threading the needle with about 5% of the hassle of trying to just stick the end of the thread through it. I hit me that this ultra teeny little spring is exactly what the doctor ordered if I was to rip it out of its coors can tab handle, and smunch it into the end of a piece of 1/16" brass tubeing, sleeve that up with 2 more sleeves to get it up to 1/8" shank, (no drill chuck needed, runs in a 1/8" collet) and bend to shape so it spun reasonably true. The tip of this could be knocked around 3/8" without permanent deforming it, by less pressure than it would take to damage the copper of the board. Deal? I'm going to make it today & find out! Of what use is imagination if you don't use it? ;-) 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> Nothing is faster than the speed of light ... To prove this to yourself, try opening the refrigerator door before the light comes on. ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! http://p.sf.net/sfu/learndevnow-d2d _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
