Re: [CAD_CAM_EDM_DRO] Re: DIY probing

Hi Chris,

The shadow technique isn't 100% but I use a commercial shadowgraph machine
for my watch making on small parts and it is good enough for that. One of
the problems I have using it on small round parts is that the light 'hugs'
the curve and diffuses a bit to give a slightly blurred edge but I can't see
that being a problem for you. At least if you get the actual curve of the
horn you will be able to adjust things with check measurements. The good
things about this method are that its simple, you get a permanent paper
record which you can re-measure any time, and it doesn't scratch the metal
by bumping metal probles into it - totally non-contact. My commercial
shadowgraph doesn't have a point source of light, by the way, it uses lenses
to try to get even illumination over the whole work surface. That is why I
suggested a 35mm slide projector (without slides!) as that is about the best
concentrated light source I have found for big areas.

Ian
--
Ian W. Wright
Sheffield UK
www.iw63.freeserve.co.uk

----- Original Message -----
From: "Christopher C Stratton" <ccs@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: 02 November 2001 14:24
Subject: Re: [CAD_CAM_EDM_DRO] Re: DIY probing


>
> It may be that I should further investigate the shadow technique. It
> needs to a be a good point light source and the light->horn path needs
> to be absolutely perpendicular to the tracing surface. After tracing,
> a few referemce measurements must be taken to scale the drawing.
>