RE:Re: re: Scanner/Digitizer skip function/probe details?

dave e wrote:

>I think Alan said something about using a dial indicator to sense Z.
>If this has a sensor (switch, optical, etc. ) on the needle then
>contact is indicated (pun intended) by movement of the needle. One
>stores x, y, and z in an array and then post-processes to correct
>sensed postion to real position: much in the same manner as one
>computes the position of contact for a ball end mill when cutting
>surfaces in Z. Hope this makes sense. :-O

Dave,

Yep, it makes sense (pun intended). The 'math part' is what CMMs' do
day in,day out...

The 'sense' part is trickier. The problem is accomodating overtravel
and multiple direction sensing. Using a 'standard indicator' means we
have to 'orient' the indicator to the correct directional position. A
small reversible dial test indicator with a switch on the needle(as
you described) will accomodate two directions with overtravel limited
by the indicators' range. For some parts (it has a SHORT arm) it may
work, as long as the 'contact' is always made in the predetermined
direction.

Remember that we are planning to probe a wide VARIETY of objects. And
we "can't" know which part of the sensing sphere(probe tip) will hit
first...

Hope this helps.

Ballendo