Building a probe

[itsme]

Hi there,

I've searched through the net and this site to try and find info on making a digitising probe. I know very little about digitising (my CNC mill isn't even running yet...), but it must be possible to make a simple probe that works reliably with reasonable accuracy.

Does anyone know what exactly is 'inside' a probe and what it would take to build one?

Thanks
Warren

[Karl_T]

http://www.indoor.flyer.co.uk/probe.htm

Karl

[ChrisJ]

Check out industrialhobbies.com

They show instructions on how to convert a edge finder that has an led light to a touch probe. I think that this type requires that you make contact with a metal surface since it is looking to sink to ground. So, if this is true, it would only be good for digitizing metal/conductive surfaces. If you wanted to do nonconductive surfaces, you would need to build a switch in the probe which when depressed (ever so slightly), would close the circuit.

Chris

[hughesbros]

I can't remember where these drawings came from. The probe works a lot better than the one MaxNC supply.
I increased the diameter on the one I built, I figured the further apart the balls were the more sensitive it would be.
The tip about tinning the PCB board improved sensitivity a lot.

Regards Mark.
Hughes Tooling.

[itsme]

Thanks for the replies everyone.

I think all this information should get me started on something. My mill isn't even finished yet and I'm already trying to find extra attachments to put onto it. I hope I have time to make something with the mill oneday, other than parts for the mill...

Thanks again

Warren

[ChrisJ]

Karl and Mark, nice probe designs.

Thanks also.

Chris

[Bloy2004]

Originally Posted by ChrisJ Check out industrialhobbies.com They show instructions on how to convert a edge finder that has an led light to a touch probe. I think that this type requires that you make contact with a metal surface since it is looking to sink to ground. So, if this is true, it would only be good for digitizing metal/conductive surfaces. If you wanted to do nonconductive surfaces, you would need to build a switch in the probe which when depressed (ever so slightly), would close the circuit. Chris

This is true... but in my limited electroplating experience, one may be able to coat the surface of non-conductive items with a conductive "paint" (spray or brush) allowing use of this type of probe. I haven't done any of this with a probe, but have had success in electroplating non-conductive items (years ago).
..of course this all depends if the item to be probed is up for the "paint job".

[ChrisJ]

Could you suggest some products that we would have access to for your conductive spray paint suggestion?

Thank you for the reply!

Chris

[Bloy2004]

Originally Posted by ChrisJ Could you suggest some products that we would have access to for your conductive spray paint suggestion? Thank you for the reply! Chris

I can't really advise on those conductive coatings....its been SOooo long ago, some of the electroplating companys are non existant now.... I DO remember though that I had made a mixture (to save a few bucks) as an alternative to the comercial coatings by using a medium to hold powdered copper. I don't recall if I fully tested it.
...geesh.. I'm not THAT old...just a bad memory or "too many irons in the fire" at that time.

[itsme]

Hughesbros, I assume that you are using TurboCNC, since you posted in the other thread I started in the TurboCNC section. Could you please tell me if your probe uses a 'point' on the end or a ball? The reason I ask, is that TurboCNC doesn't have cutter radius compensation and I'd imagine that if a ball were used, then the points written to the text file would be inaccurate. Am I correct in thinking this?

Warren

[itsme]

Hello again,

I've had a good look at all the information that was given earlier and I think I've pretty much sorted out the actual probe design in my head. My attention is now drawn to the 'amplifier'.

Is an amplifier really necessary, or can I simply run 5V through the probe directly to the parallel port? I would obviously like to make it as simple as possible, but if an amplifier is needed, then I'll have to make one.

Thanks
Warren

[hughesbros]

Originally Posted by itsme

Hughesbros, I assume that you are using TurboCNC, since you posted in the other thread I started in the TurboCNC section. Could you please tell me if your probe uses a 'point' on the end or a ball? The reason I ask, is that TurboCNC doesn't have cutter radius compensation and I'd imagine that if a ball were used, then the points written to the text file would be inaccurate. Am I correct in thinking this?

I'm using a MaxNC CL control on a machine I built. Like TurboCNC there is no compensation for the probe diameter, but I can offset the surface in Rhino. I used a 1mm diameter probe to scan the face in the image attached, the surface on the left has been offset 0.5mm inwards to compensate for the ball.

Mark
Hughes Tooling.