Re: CNC edgefinding/touch probe update

This is the setup I'm trying to do with a mitutoyo touch signal
probe. Do you have the setup information. I tried to set it up
through pin 10 with a pullup transistor but was unable to get any
response. How are you feeding the signal to turbocnc?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Kim Lux <lux@d...> wrote:
> I ordered and received the edgefinding touch probe that I spoke of
last
> week. Specifically, we purchased an Acu-rite 38-80-00-155, which
is an
> electrical contact type probe (ie between the probe stylus and the
> workpiece). The probe is self centering, with a 0.5" shank (ie
works
> with R8 collet mills...) and a 0.2" diameter tip. The stylus has
about
> 1/2" of movement in each direction in case of over run. THe probe
cost
> $250, plus shipping. I have no affiliation with Acu-rite.
>
> There are less expensive touch probes on the market, but:
>
> a) they are usually battery powered and visual, ie they light an
LED.
> b) they don't readily tie into a CNC controller, although they
could be
> made to...
> c) most have a 1" shank, ie they won't fit an R8 mill.
> d) most have a 0.4" sensing ball, which is too large for a lot of
holes.
> e) most don't do Z axis touches. The Acu-rite does.
> f) most have limited over travel capability.
>
> We mounted the the touch probe in our CNC mill, which is running
> TurboCNC as the controller. TurboCNC had a G50 command for center
> finding a hole. The G50 routine had a few bugs, which I fixed. I
also
> added a G51 routine for center finding on a protruding shaft and a
G52
> routine for edge finding on an ... edge !
>
> I've got mixed feelings about the performance of this setup.
First, the
> Acu-rite touch probe itself works well, ie it centers itself well,
has
> good over travel capabilities, etc. No problems there.
>
> The issue I have with this setup is that it utilizes an electrical
> connection between the workpiece and the probe to sense when the
edge is
> "touched". In my (limited) experience, one must have perfectly
clean
> parts in order to get repeatable results. One can get Total
Indicated
> Runout measurements of 0.0004" on a hole, but it might also take 3
or 4
> centering efforts to achieve that.
>
> I'll continue to refine our edge finding efforts. If anyone has any
> advice, I'm all ears.
>
> --
> Kim Lux <lux@d...>