RE: Probing

[Carl Mikkelsen <cmm-at-alum.mit.edu>]

At 04:19 PM 1/14/02 -0500, you wrote:
<snip>
>
>Nobody ever answered my question.  With EMC, on a hexapod, in g-cod
>can you create a temporary coordinate system where the Z axis is
>along the axis of the bit AND the head is at some arbitary roll, pitch
>& yaw?  So that subsequent position commands are with respect to this
>arbitary oriented cartesian coordinate system?
>

Unfortunately, I don't yet know what I can do under EMC with a hexapod.
I've been mostly lurking here, since I'm not yet up to speed with EMC.  I
saw the probing comments, though, and my 2c lept out of my pocket.

I need to get onto EMC, if for no other reason than that the development I
do can be shared.  I'm running with regular linux, with the clock rate
turned up to 1000 HZ.  This works well for me, especially with the new
motor drivers I should be getting back from the PCB shop in a about two weeks.

Doug (I think it was Doug) has a nice optical interrupter probe.  Thanks
for the pictures.  Your probe should give good repeatability.  I opted for
a switch (partially because I had a bag of them), and did some limited
repeatability testing.  For me, it was a good thing, as I have distroyed
three switches so far.  Programming errors have jammed them into the work
surface and crushed the switches.  As you can see from the picture, I chuck
the switch in place of a cutting tool.  Once, I got the sequences wrong and
turned on spindle power with the probe installed.  Fortunately, it wasn't
so out of balance that everything self-destructed.

This is a picture of my probe:
http://files/cgi-bin/next-res.pl?home_album=/Processed/Carl%27s%20Projects&b
asedir=./Processed/Carl%27s%20Projects/Stewart%20Platform/Truck%20Signs&res=
svga&name=PA250761.JPG&album_name=Truck%20Signs

My application was much simpler than determining the 3D shape of a model.
I needed to carve some line art, photographs, and lettering into cherry
panels.  For the photograph to look good, I needed to be able to carve
closely to the surface, which required that I know where the surface was.
Being glued-together wood boards, there was warpage and more unevenness
that I could ignore.  I used the probe to map the surface height in a grid,
and then bilinear interpolated the Z offset I needed at each point.

Does EMC include a provision for surface mapping?

-- Carl