On Sunday 03 May 2009, Erik Christiansen wrote:
>On Sun, May 03, 2009 at 09:26:40AM -0400, Gene Heskett wrote:
>> This I would do, if I ever have the problem. I have also probed for
>> contour several times and have not had any errors of more than a thou or
>> two in the data. This using the sliding tube opto-interrupter device one
>> of the guys here gave me a link to when I asked about that a couple of
>> years ago. Home- made of course. :)
>
>It's heartening to hear that it can be done without optos.
>
>Since the link http://www.hedingrips.com/Dcp00470.jpg, posted by Dean
>Hedin on 25 April 2007, now gives error 404, I was wondering if my
>imaginings of a pair of concentric tubes with a hairline aperture,
>closing on contact, are anywhere like the real thing? (I'm trying to
>figure how to have enough light for the detector when open, yet shut
>with little probe motion. Or is it just that the movement to close the
>aperture is known, and can be subtracted?)
>
>Cheers,
>Erik
I used 2 pieces of brass tubing from the model hobby store that slip inside
the next larger size. 1/4" & the next size smaller. I cut a pair of windows
in the outside 1/4" tube such that a one piece opto interrupter (ir led on one
side, ir photo-transistor looking at the led across the air gap) fit by
friction across the slots. Then in the smaller tube I cut a longer pair of
matching windows in, using diamond wheels in a dremel cuz that stuff bends
easily, too easily to saw, filled the top with solder so a ball point pen
spring could rest on it pushing it down, made a steel pointed plugin for the
bottom of it, and slid a piece of a black cable tie inside it to act as the
light valve. The outside tube is swaged in at the top just enough to trap the
ball point pen spring.
It isn't at all fancy, and if the surface its touching is slanted and slick
enough for the steel point to slide down the slant, then of course there is a
few thou of slop and it will record, using the G38 scan facility, a point a
couple of thou lower. It worked well enough to trace the floor plate in 3d
for my old deer rifle. I had visions of replacing 3oz of steel with an ounce
of alu, but it is still a "work in progress". Shoemakers kids etc. :)
If that link is down, perhaps I could go take some pix and put them on my web
page, but mine isn't quite as well finished as that one was. Or maybe that
link could be made to work again. Humm, isn't it on the wiki now, seems like
I saw it there back up the log a year or ??
As far as subtracting the movement between the tip touching and the opto
signal coming in, that is a fixed offset, zeroed out if you like by making
contact and trigger at the top of the part, and clicking on home axis. No
more offset.
--
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)
"Whatever the missing mass of the universe is, I hope it's not cockroaches!"
-- Mom
------------------------------------------------------------------------------
Register Now & Save for Velocity, the Web Performance & Operations
Conference from O'Reilly Media. Velocity features a full day of
expert-led, hands-on workshops and two days of sessions from industry
leaders in dedicated Performance & Operations tracks. Use code vel09scf
and Save an extra 15% before 5/3. http://p.sf.net/sfu/velocityconf
_______________________________________________
Emc-users mailing list
Emc-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/emc-users
