Who want to make a touch probe?

[miljnor]

well the picture isn't all that clear on your web sight.

So just to clear it up.

The coin/penny is drill thru and the bolt goes thru it?

this then rests on the pin heads for contact?

The spring pushes down on the penny/bolt for adjustment?

And the silicone is for keeping the penny from sliding around?

And from what I gather the silicone goes around the prob inside of the shaft hole underneath the pins???

[10bulls]

well the picture isn't all that clear on your web sight.

Sorry, it had been drinking, I'll have words with it.

The coin/penny is drill thru and the bolt goes thru it?

Yes, so that the head is against the top (unfaced face).

this then rests on the pin heads for contact?

Yes, like a dolmen.

The spring pushes down on the penny/bolt for adjustment?

Yes

And the silicone is for keeping the penny from sliding around?

Yes. To be honest, I haven't put any on the prototype, but I thought it would be a good idea as if the probe gets pushed sideways the disk
can rub against the inside of the cylinder and hang.

And from what I gather the silicone goes around the prob inside of the shaft hole underneath the pins???

I would put it outside. That way you can put it on afterwards when you're happy it's working. Or you could use a small piece of silicon tube maybe.

[turmite]

10Bulls is it still working? Are you gonna post plans?

Mike

[greybeard]

10 bulls - just a thought. Had you considered substituting a small cylinder of foam rubber for the spring ?
I see the spring as being asymetrical in its pressure on the penny, and the foam could also act as a seal above it. The foam could be stuck to the penny for location, and a second piece underneath the pin assembly could as as a lower dust seal.
John

[10bulls]

10Bulls is it still working? Are you gonna post plans?

Yes, the scan completed with not one hang. The plans (such as they are) are on on the web link in post #39.

[10bulls]

10 bulls - just a thought. Had you considered substituting a small cylinder of foam rubber for the spring ?

Yes, in fact MrBean's Mk I probe had a piece of foam for a spring.
It would certainly work and I like the idea of gluing it to the disk to help prevent sideways movement.
The design lends itself to tinkering and using what's lying around.

[sdantonio]

All the commercial scanners and computer controlled measuring systems uses tools with ball tips. Shouldn't be a big problem to put a ball bearing ball at the end of the tip.

Actually I had a brilliant idea the other night. Traditional violin makers, when they see an instrument where they want to preserve as much information as they can, make up a plaster mold cast directly from the instrument. Modern materials allow us to use a combination of silicone rubber (which will not stick to varnished surfaces) and urethane polymer to make the final casting.

A violin maker I know in NYC tells me that his sillicone/urethane castings come out so accurate that they preserve even the smallest imperfections in the surface like chipped varnish, etc.

So I make a urethane casting, then use the touch prove on that. And I can be as rough with that as I want. Couldn't be simpler.

[N4NV]

So I make a urethane casting, then use the touch prove on that. And I can be as rough with that as I want. Couldn't be simpler.

Where do you get the casting material? Any brands you prefer?

Vince

[sdantonio]

This is my source for urethane and silicone rubber http://www.jgreer.com/ There was a paper published a couple of years ago in the journal of the violin society of america detailing the process (actually it is the transcription of a talk given by a violin maker from NYC of the method he uses. Prior to these materials it was plaster castings. I used to have a hard copy before the big hard drive crash of last summer (damn maxtor). This isn't the same paper but I found it with a quick google. http://www.abcviolins.com/moulds1.html

[sdantonio]

Oh yeah Vince. Always test on scrap wood first (john's source material sometimes changes).

[arie kabaalstra]

intresting Topic, i get the picture, i'll start working on my own little probe..

[Giacco]

idea!

It is possible to place this switch in the top of the Indicator and the design could be simplified.

Regards.

Se le puede colocar este interruptor en el tope del indicador y se pude simplificar el diseño.

Saludos.

Tactile Switch (tipo mouse): http://www.jameco.com/webapp/wcs/sto...oductId=119010

[arie kabaalstra]

i'm not sure this will work, since it can only switch when pressed on, , and how are you gonna design a system that triggers the switch, nomatter which way you move the probe?..

anyways, to make a long story short, i've made my own probe already only 25 mm in diameter, repeatability within 0.005 mm, so i think it's accurate..

http://i12.photobucket.com/albums/a2...1/DSC_0473.jpg

http://i12.photobucket.com/albums/a2...1/DSC_0462.jpg

[icupeter]

idea!

It is possible to place this switch in the top of the Indicator and the design could be simplified.

Regards.

Se le puede colocar este interruptor en el tope del indicador y se pude simplificar el diseño.

Saludos.

Tactile Switch (tipo mouse): http://www.jameco.com/webapp/wcs/sto...oductId=119010

I ripped apart a few computer mice the other day looking to grab some parts for my new edge detector/probe. I had three Logitech mice and they all used OMRON mini-switches. I think it would be hard to adjust as there is quite a bit of hysteresis between off and on.
Looking at other parts of the mouse though the X-Y IR detection circuits are interesting. I am going to use a few of these positioned at 120 deg. and one on top of the probe shaft for Z-axis touch. With a small hole in the pcb about the size of a sewing pin it should work. Designing an adjustment method now.

[Giacco]

Esta es mi idea

This is my idea

Saludos.

[turmite]

Hello Giacco,

Beautiful design.......but I see a potential problem. Your probe has no clearence for side to side movement and will only work in straight up and down probe movement. Some of the scan software has a feature that uses the side of the probe tip as much or more than it uses the end. I have a commercial probe and it has about 2mm clearence all the way around the probe shank where it comes out of the body of the probe. When using an extension for a total of 2" of shank I have quite a bit of overall movement at the tip when pressed from side to side. This allows for overtravel and helps to keep from damaging the probe while in use.

Mike

[arie kabaalstra]

that's why i think a 3point setup is the best ( and i made my drawings just for that setup ), the slightest motion wil cause any of the 3 switches to break circuit, and thus giving the control a sign "hey!!.. something's touching!"

if you increase the diameter of the disc that operates the switch, it might even do "side probing" but i'm not sure it will be very accurate..

[Giacco]

Es verdad, ya comprendo el funcionamiento.

It is true, already I understand the functioning.

Regards.

[Giacco]

Second Prototype, changing concept. The sensibility might be controlled by means of the screws of adjustment. The circuit would be closed to the contact from any side. Suggestions please.
Regards.

Segundo Prototipo, cambiando concepto. La sensibilidad se podría controlar por medio de los tornillos de ajuste. El circuito se cerraría al contacto desde cualquier lado. Sugerencias por favor.
Saludos.

[svenakela]

Giacco, I really like your engagement in the topic, but I think it's not the best solution.
The problem is that if an unexpected hit occur, the tip will be bent. The design with three pair of balls is a lot more flexible. Also it's self-aligning, the tip will be forced to fall back to same position even after a big move.
The big CMM companies also have flexible tip tools that allows several millimetres of travel.

Regards,
Sven