I made this somewhat crude optical probe: http://www.hedingrips.com/Dcp00470.jpg
It's deceptively simple, but it actually works very well and is very repeatable. It only triggers in the downward motion of the spindle. The "Renishaw type" probe that Dave mentioned can trigger from a sideways motion. This one cannot, but of course that requirement may not be needed for what you are doing. The picture bears further explanation. The optical sensor "stradles" the larger tube, and is a tight, interference fit. The small black plastic piece in the smaller id tube the optical "interrupter". When the sensor is in place the smaller tube is captivated (it can't be pulled all the way out of the larger id tube) but can still telescope upward into the larger tube. There is a spring inside the larger tube, pushing the smaller tube downward. A rolled lip on the end of the larger tube keeps the spring in place. The larger tube gets mounted in my router collet. The large tube is 1/4" od. On the end of the smaller tube I mount various probe tips that match the contours of the assorted router bits that I use on my machine. I turned these on a metal lathe. For example , I made one like 3/8" ball mill, standard 3/8" & 1/4" endmills, etc... These are not shown in the photo. The small black plastic piece is an interference fit inside the smaller tube. Its position is adjusted so that the slightest movement of the smaller tube will trigger the optical sensor. As I recall, I have a pullup resistor on the top side of the transistor and it constantly pulls the parallel port pin low, except when it is interrupted. I can't think of cheaper solution than this. The sensor I had in my junkbox, but you can find similiar ones out of the digikey catalog. The brass tube you can get from the hobby store or perhaps salvage from an old telescoping antenna. I have only done probing with EMC1, Dave seems to indicate in his post that it is now possible with EMC2. I was not aware of this. I guess it's time to for me to upgrade. As it stands now, Probing a surface with EMC is a slow proccess. So it is worth mentioning the other options for aquiring 3d surface data: I've played with this, it's practically free but takes some work in cleaning up the aquired data. http://www.cs.tu-bs.de/rob/david.html And then there are digitizing arms. http://www.immersion.com/digitizer/ These are exspensive. I think the digitizing arm coupled with good CAD software that can extrude surfaces is probably the most effective and rapid solution for the types of projects we have in mind. ----- Original Message ----- From: "Gene Heskett" <[EMAIL PROTECTED]> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Tuesday, April 24, 2007 8:59 PM Subject: [Emc-users] Need a contour finder probe > Greetings; > > Has anyone drawn up a probe of the sort one could mount in the spindle > collet, > hook up to emc so that when contact has been achieved, emc records the > location? > > And, assuming this has been done, has the scanner routine to do this > already > been written too? > > I'm thinking in terms of the engraving done on a bolt rifles floor plate, > or > trigger guard, so that if an interesting pattern could be scanned with > potrace, and then the z axis treatment added so as to carve, say with a > small > diamond burr moving at call me next week speeds, to a consistent depth of > say .005", the pattern obtained with potrace, but on a curved surface such > as > the bottom of a trigger guard or floor plate. > > But I'd need to be able to probe the contour of the item, and do it > without > doing any preliminary damage to the blueing, which is not a very good > electrical contact surface. So I'm thinking in terms of a guided needle > whose upper end can be set against a single button of a conductive > elastomer > keyboard switch, the effect of which would be rather like a potentiometer > as > the pressure increases, and we could trip and stop the z axis descent when > a > logic 0 was detected, record all 3 axis's positions, then reverse the z > drive, move to the next position .005 away in the scan, and repeat. > > It seems like we ought to be able to do that if the contact pressure > sensor is > already a working item. > > Anybody care to share insights/drawings for such a beast/tool? > > -- > 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) > Nothing is finished until the paperwork is done. > > ------------------------------------------------------------------------- > This SF.net email is sponsored by DB2 Express > Download DB2 Express C - the FREE version of DB2 express and take > control of your XML. No limits. Just data. Click to get it now. > http://sourceforge.net/powerbar/db2/ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. 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