On Wednesday 25 April 2007, Dean Hedin wrote: >I made this somewhat crude optical probe: >http://www.hedingrips.com/Dcp00470.jpg > Now that's neat, and I believe the hobby store has those brass tubes in suitable telescoping fit sizes, so this looks exactly as if it will do the job.
Thank you. >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. Me either. I'd made a similar device out of discretes, but had to use two of the rectangular photo transistors stacked, in parallel to get sufficient linearity of the control signal, which was being fed to one of those $20 stepper kits. It straddled the beam on my old OHaus 505 scale, the stepper motor kit being controlled drives a 1/4" brass tube run cross ways at a slight downward angle through a std 8 oz plastic drinking glass, and has several 1/8" holes drilled through the tube as it passes through the glass on its way to hanging over the scale pan. The back end of the tube has been soldered shut, and a flywheel from an elderly 5.25" disk drive is setscrewed to it, with the motor driving the belt stolen from that same donor disk drive. As the beam rises toward balance, the motor stops within 1/20 grain of the correct weight in the pan, but I have to prop the beam up with a weak spring that is out of contact with the bottom of the beam by then else the weight response is so slow it will overshoot half a grain. Why did I do it? Just because I could, and weighting the powder for more than a 20 round box of shells for Bertha gets to be a chore. Bertha being the P.O.Ackley-06 I built about 45 years ago, on a P17 action sitting in a laminated walnut thumbhole stock I carved, and now on its 3rd barrel & due for another fresh one as the groups are slowly opening up again. Douglas barrels seem to be about 2000 round barrels in 30 caliber. Old meat in the pot/freezer at about 75 kills, but at my age, its 13 pounds with its glass is becoming a chore to haul around come deer season, but it still gets to the range for maybe 200 rounds a year. About 3 years after I built it, it reached out and touched a heck of a buck with the 2nd and 3rd shots going though his liver about 3" apart, 640 yards away, deduced by running the Speer ballistics slide rule backwards, easy when you know the velocity and bc of the bullet. The holdover was about 10 feet, and about 15 feet into the wind. Nice buck. The first shot? I actually saw the bullet going in the scope! Kicked up some dust about a foot behind him, so I just moved over and up to the next clump of saw grass for an aiming point. After the third I just laid there and watched for about a minute because it looked like the third had gone through him, then he started batting at flies in his side and I was able to finally see a streak of red. Feeling cocky (& one of the ranch hands had arrived by then so you have to do it right when in front of the frogs you know,) I stood up and picked up my coat and hat and told Bill to go bring the pickup to the head of that ridge and bring the tote goat down, I was going to go down and dress him out, he'd be laying there when I got there. Still standing when I said it, he was laying there when I got there about 15 minutes later. I love it when plan A works. :) >The sensor I had in my junkbox, but you can find similiar ones out of the >digikey catalog. I don't think I have anything that big in my junkbox unless it might be in an old disk drive & I haven't discovered it yet. Digikey is a phone call away once the right one is found in their online 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. And I don't have forever, as I'm 72 now. :-) >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 Not to mention a video speed a/d in the path, and enough bandwidth between it and the drive surface. >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. Probably, but that takes a little red wagonload of coins removed from the laundromat machines to play in that game. I'll have to pass for obvious reasons. Thanks Dean. I think this is exactly what I need, and the optical interrupter approach is not something that had crossed my mind yet, particularly in this simple a device. >----- Original Message ----- >From: "Gene Heskett" <[EMAIL PROTECTED]> >To: "Enhanced Machine Controller (EMC)" <[email protected]> >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 >> [email protected] >> 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. Click to get it now. >http://sourceforge.net/powerbar/db2/ >_______________________________________________ >Emc-users mailing list >[email protected] >https://lists.sourceforge.net/lists/listinfo/emc-users -- 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) Lo! Men have become the tool of their tools. -- Henry David Thoreau ------------------------------------------------------------------------- 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 [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
