Re: [CAD_CAM_EDM_DRO] Re: Digitizers, Renishaw

I think you might be able to use a gunsmithing/potography trick with those
opto set ups.

First you mask (black out) the end of the pick up unit with some sort of
disk (or possibly a short length of "rod") glued in place. Put a VERY TINY
pinhole in the disk (rod) to allow light to come thru.

Mount mirror on the end of the probe, with the probe free to move angularly
when it contacts a surface. With a small enough pinhole thru a thick enough
disk, the angular movement should be enough to block light return to the
opto unit. The probe would need to be free enough to move yet be able to
return to center position CONSISENTLY when the probe has been moved away
from contact with the part. It might be necessary to increase the movement
of the mirror by mounting it on the end of a "multiplier arm" between the
probe and the sensor rather than directly on the end of the probe.

How much "adjusting" it would take remains to be seen.

Smoke


-----Original Message-----
From: Ian Wright <Ian@...>
To: CAD_CAM_EDM_DRO@egroups.com <CAD_CAM_EDM_DRO@egroups.com>
Date: Thursday, January 11, 2001 5:12 PM
Subject: Re: [CAD_CAM_EDM_DRO] Re: Digitizers, Renishaw

>Hi Jon,
>
>The only way you could get a similar accuracy using an opto set-up would be
>to make the disk very wide relative to the length of the probe and put tiny
>shutters at its periphery between LED/opto sensors. This would probably

work

>but, you would have a big problem in preventing the disk rotating whilst
>keeping the movement light enough.
>
>Ian
>--
>Ian W. Wright
>Sheffield UK
>www.iw63.freeserve.co.uk
>----- Original Message -----
>From: "Jon Elson" <jmelson@...>
>To: <CAD_CAM_EDM_DRO@egroups.com>
>Sent: 11 January 2001 19:56
>Subject: Re: [CAD_CAM_EDM_DRO] Re: Digitizers, Renishaw
>
>
>>
>> Well, there's the rub. The Renishaw design causes an open
>> circuit when the contact probe is moved .0002" in ANY
>> direction. I can see how this will work with an electrical contact
>> between two hard, rigid parts. I can also see how bad contact
>> could occur, as you say.
>>
>> I don't see an easy way to make a low-force probe that will detect
>> such tiny motion in any direction by optical means.
>>
>> Renishaw obviously solved this problem, and have been making
>> these devices for many years.
>>
>> Jon
>>
>>
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>
>Welcome to CAD_CAM_EDM_DRO@...,an unmoderated list for the

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