Homemade Renishaw style touch probe.

[tonyfoale]

The net is full of example of DIY touch probes, but when I searched this forum I did not find any examples so here is a post describing one that I made a couple of days back, along with an explanation of how they work and what you need to make them work well. I also describe how I checked for accuracy.

Click for full size.
This picture shows a typical use that I have for it. Inspecting a motorcycle crankcase that I made from a solid block.

These probes have numerous uses such as reverse engineering parts, setting workpiece positions prior to machining, 3D surface scanning and part inspection. First invented in the early 1970s for a difficult inspection job on Concorde engines, they are now widely used on milling machines and CMMs (Coordinate Measuring Machines). Some top of the range versions have sub micron accuracies. I was aiming for mine to be better than the 10 micron resolution of the slides and DROs on my mill. Testing showed that I was successful.


The important bits.

For the full story see a PDF document at https://motochassis.com/FileDump/CNC_Probe.pdf

If I get a moment over the weekend I'll make a video showing the testing procedures.

[Altair]

Thanks tonyfoale! We've added your Touch Probe to our CNC category,
as well as to your builder page: tonyfoale's Homemade Tools. Your receipt:

Touch Probe by tonyfoale

tags: CNC, test probes

[tonyfoale]

The probe has now been finished off with the addition of a 3D printed box to contain the minimal electronics. This makes it self contained except for a 5v wall wart when using it manually. There is an output for connecting to a CNC or other external device when necessary. The schematic for the electronics is in the PDF linked in the first post, otherwise the following pix are self explanatory.

Click images for full size.



The box could have been made smaller, but the excess volume is just future proofing.

[olderdan]

Great addition to your measuring equipment and a very neat job, I was never quite sure what was inside those touch probes although I have used them in the past on CMMs. I am sure you will be using yours a lot.
BTW your crankcases are looking fantastic.
Regards
Alan

[tonyfoale]

Great addition to your measuring equipment and a very neat job, I was never quite sure what was inside those touch probes although I have used them in the past on CMMs. I am sure you will be using yours a lot.
BTW your crankcases are looking fantastic.
Regards
Alan

Alan,

Many thanks.
I put a link on my Facebook about it and it caught the eye of a Renishaw engineer. He has given it a seal of approval, as far as can be determined by words and photos. He confirmed that my effort is similar to their early continuity probes, nowadays they have different technologies including strain gauge detection of touch. He offered the opinion that mine should be good for around 5 microns repeatability. I know that it is better than 10.
You can see his comments if you scroll down to the fifth post on Tony's FB . You may need to click on "See more comments"