re:rE:Re:RE: digitiser
Posted by
ballendo@y...
on 2001-01-12 17:45:36 UTC
Smoke wrote:
I mentioned before that you can constrain a movement (very
accurately) one direction, whilst allowing movement in the opposite
direction. I gave the example of R/C joysticks.
In this case, you could use a similar approach. Think of the 'ball'
catches on cabinets, or the ball plungers used in fixtures and jigs.
These consist of a casing, a spring, and a ball. The casing 'holds
the ball' "in", whilst the spring pushes it out. Therefore the ball
(or plunger,which usually has a rounded 'ball' tip) is repeatable in
one direction and compliant (moves to accomodate overtravel) in the
other direction.
Now it just happens that these ball plungers are commonly available:
Try reid tool, jergens, other industrial(machine shop) suppliers.
They are threaded on the outside (like the proximity switches you may
already be familiar with) and available in various 'forces'.
They could be used as the contacts TOO, or just as the 'centering'
mechanism. If so, a probe will be a non-conductive block with 3
threaded holes, and one counterbored hole (from top to bottom) for
the ball-ended probe. Above the ball (in the counterbore) will be the
spring mentioned in the previous post, with a cap screwed on top to
contain it. The three plungers will be 'adjusted' for centering. Then
3 contact points (which could be sharp point screws) are similarly
screwed in (from the sides) and adjusted.
Hope this helps.
Ballendo
P.S. Personally, I'm looking at when the renishaw patent(s) expire,
and until then, I'll probably make one of their early-style probes
for my own use!
P.S.S. Anyone know why RUBY is used for probe tips??? I think I had
said (mistakenly) sapphire before...
>The probe needs to be made of a spring quality (high carbon) steelDigitiser thread people,
>or some other flexible material
>>ptengin@a... wrote:
>>I'd be interested - I'm wondering what makes the probe hang down
>>exactly vertically, and if it is so constrained vertically, what
>>enables it to flex sideways without breaking if it runs sideways
>>into the vertical edge of the object.
I mentioned before that you can constrain a movement (very
accurately) one direction, whilst allowing movement in the opposite
direction. I gave the example of R/C joysticks.
In this case, you could use a similar approach. Think of the 'ball'
catches on cabinets, or the ball plungers used in fixtures and jigs.
These consist of a casing, a spring, and a ball. The casing 'holds
the ball' "in", whilst the spring pushes it out. Therefore the ball
(or plunger,which usually has a rounded 'ball' tip) is repeatable in
one direction and compliant (moves to accomodate overtravel) in the
other direction.
Now it just happens that these ball plungers are commonly available:
Try reid tool, jergens, other industrial(machine shop) suppliers.
They are threaded on the outside (like the proximity switches you may
already be familiar with) and available in various 'forces'.
They could be used as the contacts TOO, or just as the 'centering'
mechanism. If so, a probe will be a non-conductive block with 3
threaded holes, and one counterbored hole (from top to bottom) for
the ball-ended probe. Above the ball (in the counterbore) will be the
spring mentioned in the previous post, with a cap screwed on top to
contain it. The three plungers will be 'adjusted' for centering. Then
3 contact points (which could be sharp point screws) are similarly
screwed in (from the sides) and adjusted.
Hope this helps.
Ballendo
P.S. Personally, I'm looking at when the renishaw patent(s) expire,
and until then, I'll probably make one of their early-style probes
for my own use!
P.S.S. Anyone know why RUBY is used for probe tips??? I think I had
said (mistakenly) sapphire before...