Re: [CAD_CAM_EDM_DRO] Re: Coordinate Measuring Machine - home brew renshaw probe

On Dec 3, 2011, at 10:05 PM, Danny Miller <dannym@...> wrote:

> I was looking at the problem myself, since touch probes are quite expensive.
>
> There's two problems here in DIY. Getting basic "relative" accuracy is
> not a problem, even with fairly crude gear. That is, I can chuck the
> thing up, lock the spindle, scan a wrench and get an accurate point
> cloud of the wrench, all the points should be accurate relative to one
> another.
>
> But another purpose is absolute accuracy on the axes. For example, I
> have a piece of work with a predrilled hole I want to line up with.
> There's scripts where you can say "find me the exact center of this
> hole" and I'll use that as an origin for my coordinate system for the
> rest of the milling operations. The problem is, if there's any runout
> where the probe tip is NOT exactly inline with the center of spindle
> rotation, then it's not actually the center of the hole.
>
> Or just "find the surface height of a flat thing I just chucked in
> there"- which doesn't involve runout, but any difference between the
> height of the chucked probe and the height of the final milling bit
> renders the reference inaccurate.
>
> I think rather than absolutely perfect machining, the key is to make it
> adjustable so the runout can be fixed as needed, and consistent in that
> thermal expansion won't lead to significant errors.
>
> Danny
>
> On 12/3/2011 8:35 PM, Michael Fagan wrote:
> > Sounds like he is trying to simulate a commercial CMM, not scan a surface.
> >
> > Sent from a mobile device.
> > On Dec 3, 2011 8:48 PM, "turbulatordude"<dave_mucha@...> wrote:
> >
> >> **
> >>
> >>
> >> http://www.indoor.flyer.co.uk/probe.htm
> >>
> >> here is a link to one guy who made one.
> >>
> >> the touch probe can take hours to probe a surface.
> >>
> >> if laser is possible for your project, consider that as a faster and
> >> cheaper way to go.
> >>
> >> Dave
> >>
> >> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ime029"<ime029@...> wrote:
> >>> I m making a CMM trainer as my final year engineering project... i m
> >> facing problems.. reinshaw probes are very expensive and not economically
> >> feasible for a trainer..
> >>>
> >>> any idea?
> >>>
> >>
> >>
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
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