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Better touch probe

For the object scanning I want to do I would like a touch probe with more capability than the $5 touch probe.

Having had a good look around at what was happening in the DIY touch probe world. It would seem that a lot of the designs are based on the now expired patents of a touch probe company.


The above is an image from Bertho Roman that shows the mechanism clearly. The three spokes sit on the ball bearings and close the circuit. Whenever the probe is disturbed one of the spokes will move off the ball bearings and break the circuit.

This mechanism is an example of a kinematic coupling. There are two forms of the Kinematic coupling.


The above image comes from precisionballs.com. It would seem from reading peoples comments on touch probes they have built themselves that the can be unreliable electrically. I thought that it would be interesting to see what could be lashed together using not the six ball solution but the three ball and six rod type coupling.

I'm putting together a quick and dirty hack using some large washers on which the mechanism is built. I'm planning to use the shank of copper coated pop rivets for the rods glued down to an insulating layer over the large washer. Rather than use use ball bearings I am planning to use the top of a 1/8 dome nut.

This will be interesting to see the difference in performance between this mechanism and the $5 microswitch version.

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