On Tuesday 27 October 2009, Chris Epicier wrote: >Jeff > >I read your post with great interest. For me, it gave some very good > insight. Like you, I do not have a repeatable tool length. I was wondering > if I could get a kind of switch doing my touching off of the z-axis. The > idea is as follows: > >- I have a parallel port based 3 axis mill driven by emc2 2.3.3 (soon > 2.3.4) - I have a vacuum table, that is well enough even (I remill the > surface when the wear plate needs to be replaced) - x and y are also > repeatably within reference distance from home position - If I would add a > small metal plate (say alu) into my vac table (could veven be on an spring > mount), connect it to a wire, I could close an electric circuit when the > tool touches that plate.
I would not recommend using alu for that due to the oxide coat that forms on the alu about 100 microseconds after it is scratched to expose the metal. To use it that way would require enough contact force to penetrate this oxide layer and actually make a connection at 3 to 4 volts of applied voltage. That contact pressure could be sufficient to damage the edge of the bit, reducing its life. A gold or silver plated copper contact would be hundreds of times more reliable at touch pressures that would not damage the surface or the bit. A piece of the gold plated contact finger pattern sawn from an old computer card and glued to the reference point, with the sensor wire soldered to it would make a good contact than would be very repeatable at least until the cleaning of the area wore away the gold flash. > If I was able to stop z-motion based on the > closed electrical curcuit (we talk about say dc 4-6V) immediately, I would > not have to jog to the position each time. This saves considerable time > for me and sounds much more reliable to me as manual jogging. Perhaps some use might be made of the G38.2 command by somehow linking the contact detection to the axis zero? I'm not an expert on that, don't even play one on tv, so I'll let the smarter folks here address that. :) But, when they have sorted this, its definitely something I could use too. >How would I be able to implement this? > >greets Chris -- 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) The NRA is offering FREE Associate memberships to anyone who wants them. <https://www.nrahq.org/nrabonus/accept-membership.asp> Beware of low-flying butterflies. ------------------------------------------------------------------------------ Come build with us! The BlackBerry(R) Developer Conference in SF, CA is the only developer event you need to attend this year. Jumpstart your developing skills, take BlackBerry mobile applications to market and stay ahead of the curve. Join us from November 9 - 12, 2009. Register now! http://p.sf.net/sfu/devconference _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
