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

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?
>>>
>>
>>
>
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