<http://www.isd.mel.nist.gov/personnel/kramer/pubs/RS274NGC_3.web/
RS274NGC_33a.html>
describes G38.2 use etc.
see: 3.5.9 Straight Probe - G38.2
3.5.9.1 The Straight Probe Command
and 3.5.9.2
<http://www.linuxcnc.org/docs/html/config/emc2hal/emc2hal.html>
motion.probe-input IN bit
G38.2 uses the value on this pin to determine when the probe has made
contact. TRUE for probe contact closed (touching), FALSE for probe
contact open.
There is more out there someplace e.g. program to probe a hole ,etc
and a description of the program to log position values but I've not
found them.
HTH
Dave
On Apr 25, 2007, at 2:25 AM, Gene Heskett wrote:
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)" <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
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. 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
--
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
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. 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
