Digitising Probe.

[Clive HartlandParticipant @clivehartland94829]

Has anyone on the Forum made one of Shaun Wainfords Digitising Probes, I have downloaded the diagrams/drawings and now realise it is connected to the software for digitising.

My query is can it be used in a standalone method by attaching an LED and some method of powering it?

I understand its function/workings and feel confident in making one but am a bit put off because it needs attaching to software that I have not got.

Clive

[Clive HartlandParticipant @clivehartland94829]

[John Stevenson 1Participant @johnstevenson1]

Clive, got some links to save hunting about ?

[Clive HartlandParticipant @clivehartland94829]

I found it by googling Shaun Wainfield and going down the headings to the Digital Probe.

He is big in CNC machining and making 1 off Motor Cycles from home made parts.

There are a couple of other mentions in other engineering forums also.

Clive

Edited By Clive Hartland on 22/09/2012 10:48:38

[Clive HartlandParticipant @clivehartland94829]

Another link is 'Homebrew Touch probe'. This details a simple circuit to fit in a probe.

Clive

[blowlampParticipant @blowlamp]

Clive.

It is a nice design, so as it's only a glorified switch, you should be able to rig up something to get what you're after.

I'm no electrcal expert, but you'll need to keep in mind the tendency of the contacts to tarnish/burn to the degree that the connection becomes unreliable, so very low current flow is probably what is needed.

Martin.

[John Stevenson 1Participant @johnstevenson1]

Clive,

OK thanks now see that it's just a CNC touch probe.

What is not quite clear to me now is how you want to use it given no CNC ?

It could be used manually but it would be an absolute pain, move X and Y using a DRO ? bring Z down and note the reading, move on and repeat. This would give you what is known as a point cloud map but without software or CNC what use is it?

Perhaps I'm reading this all wrong and all you want is an edge finder or similar ?

[GoCreateParticipant @gocreate]

Hi Clive/John

Clive, I don't mean to hyjack your thread but if I may, can I direct a question to John. I am interested in this probe for cnc probing with Mach Cloud software..

John, From what your saying, this probe is only really suitable when the contacts break in the Z travel (having previously moved to an X/Y position) so would not be suitable for edge finding in the X, Y, axis only? (So should only be used for 3D digitising?)

Cheers

Nigel

[John Stevenson 1Participant @johnstevenson1]

Nigel,

No they will work as an edge finder, they have three sets of contacts that the probe sits on and it only has to move off one to break contact.

Imagine you are probing a steep cone like a church steeple when it goes down and makes contact the movement will be more X or Y than Z due to the angle. Hope I have explained it clear enough ?

John S.

[GoCreateParticipant @gocreate]

John, Thanks, that's clear to me now.

Cheers

Nigel

[Les Jones 1Participant @lesjones1]

Hi all,
Here is an idea for a variation on this design. A ball on the end of the probe sits in a conical depression on the end of a rod. It is held in contact with the depression with an insulaing fibre passing through a hole in the rod and attached to a tension spring. The origin idea was that the rod was made of three 120 Deg segments with thin insulators between them. If the ball was not displaced it would make contact with all three segments. If it was diplaced from any direction it would no longer make contact with all three segments. I could not see an easy way to make the rod in three segments so a possible alternative would be to make the rod of insulating material and drill three holes down it spaced at 120 Deg. Three thin metal rods would then be glued into these holes. When the glue had set the end of the rods would be machined so they formed part of a conical depression. The ball could sit in contact with the end of these rods. Here is a sketch of the idea.

I have not yet tried to make one of these to test if the idea will work.

Les.

[John Stevenson 1Participant @johnstevenson1]

Les.

It will work but not very accurately due to the size of the ball and length of the probe.

Now if you made the ball 2" diameter…………………..

[blowlampParticipant @blowlamp]

Here's a cheap one

Martin.

[Clive HartlandParticipant @clivehartland94829]

So basically John i would be better using an edge finder of the mechanical type ?

The idea partly, was to make one and get it to work for edge finding. But as you say it would be tediously slow and only in x and y modes.

Its an interesting project that would probably sit on the shelf doing nothing, so that one is on the back burner !

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Clive,

I think it's worth reading through this recent thread.

MichaelG.

[Anonymous]

Posted by blowlamp on 22/09/2012 11:31:57:

I'm no electrcal expert, but you'll need to keep in mind the tendency of the contacts to tarnish/burn to the degree that the connection becomes unreliable, so very low current flow is probably what is needed.

Quite the reverse in fact. Most mechanical switches and relays incorporate a wiping action to the contacts as they close to help break the very thin oxidation layer. There is also normally a minimum wetting current through the contacts to ensure reliable current flow once mechanical contact is made. For small switches I use a minimum of 10mA as a rule of thumb.

Regards,

Andrew

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