DIY Touch probe , Renishaw Tip


(Chris) #1

I have an idea for a Mini Touch probe like the Renishaw’s but with 1/4’’ shank.

My question is I have no idea how the circuit/electrical stuff works. When you plug the 2pin JST into “Probe” does carbide motion pick up only on when the circuit completes? Is there a way to set it up so it can register when a circuit breaks?

Here is my inspiration: https://hackaday.com/2011/06/09/diy-cnc-touch-probe/

Could something like this work on the nomad/shapeoko board?


(Richard Cournoyer) #2

Does this help?


(William Adams) #3

I believe for a normally closed Probe you have to recompile Grbl.

See https://www.shapeoko.com/wiki/index.php/Upgrade_Overview#Touch_.2F_digitizer_Probe for some links and notes on this.


(Evan Day) #4

So this is on my future project list of things to make and has been for a while. So bearing in mind that I have not actually made one yet, this is what I have gathered from lots of research:

  1. This 3-bar design has hundreds of variations out there but the same basic design seems to be the most popular for homemade models. I found a few others that use a piezo buzzer and an inverting Schmitt trigger type of electronic circuit, which I think may be more accurate but I’m afraid that its just at the threshold of my electronics comprehension level, so the 3 bar design is the way I’m going to go.

  2. For this design, I believe a critical step is having some sort of mechanism to limit runout; the design you reference uses set screws. This is really important to make the probe accurate enough.

  3. Obviously Carbide Motion doesn’t provide the auto level functionality required to use a probe like this. I’m currently using a Carbide 3D touch probe, which is really good for zeroing, but I don’t want to use it for auto leveling. For auto level, I believe you will need to use an alternate G-code sender like bCNC (the one I’m currently trying to force myself to learn), or Chilipeppr. I’m not sure what other senders have the auto leveling functionality.

  4. If you just need a probe for zeroing, frankly the probe design you reference is much more complicated than required. Much easier ways to make your own touch probe, or use a Triquetra, or Carbide 3D probe.

  5. But yes, I believe a probe like that would work with the existing Shapeoko board and the existing probe pins. The biggest question I don’t know the answer to is this: I believe that one pin on the probe part of the board supplies +5V. These probes work by detecting when there is a break in that +5V signal. What I don’t know is if the control board is set up to detect a drop of 5V or if it is looking for an increase to 5V from 0V.


(Phil Thien) #5

I don’t understand why one would be using this sort of device instead of just relying on the bit?

What is the advantage of this thing?


(Phil Gorsuch) #6

I have looked at doing this as well. About the only thing that has really stopped me other than a lack of time is the limited Z travel of the Nomad, which means one would have to make a very very compact probe if you wished to probe material of any height. Ultimately Carbide Motion will not cut it for this type of probe interaction (Eg auto leveling, automatically finding hole centres, stock centres etc.). I was planning on looking into bcnc or others that allow customization.


(Evan Day) #7

Phil Thien, auto leveling. Very useful for PCB engraving, or engraving very thin lines where you need to know if your surface of the work piece has any distortions or changes in Z-height. Also enables working on curved surfaces without a 4-axis rotation. You also can use it for making a digitized model of an actual object.

Engraving on a curve: https://www.youtube.com/watch?v=dgqRBbZXwIA

Digitizing an object: https://www.youtube.com/watch?v=ZYJU1kwtzV4


(Richard Cournoyer) #8

Because technically there is a small chance of damaging the cutter. In fact, I was taught to never measure the size of a carbide end mill using a micrometer…again, it can cause (micro) damage.


(Griff Carpenter) #9

Interesting Evan. I look forward to following your eventual progress on this.


(Neil Ferreri) #10

@RichCournoyer How do you measure end mills? Plastic calipers?


(Richard Cournoyer) #11

No dear, we use an Optical Comparator.


(Neil Ferreri) #12

Well, of course. I think I left mine in my other pants, though.


(Griff Carpenter) #13

Oh man, gotta look that up. An optical whozit.

Lowly woodworker here, just muddilin’ through all this tech stuff.


(Chris) #14

Thanks for the replies everyone! It is very helpful.

I am actually making a touch plate already, the touch probe is something that interest me as well. This is less about what is needed, and more about what am I good enough to make. Self challenge if you will. I’m currently enrolled in an program and have access to big machines so I’m trying to take advantage of this by having projects on standby.

I’m currently designing a touch probe and I have it around 2’’-ish in length, so next step is to 3D print and test.

This is probably 4th on my list, behind a wall of workholding things for the nomad.


(Dan Nelson) #15

I think my QA manager would have a fit if I turned up with my tooling at his office and asked to use his optical comparator. They were not very keen on me rolling my motorcycle in to take some measurements on their FARO arm for some pieces I wanted to make either,…stifling my progress!!!

:smile:

Dan


(Griff Carpenter) #16

Blue tape and CA, walls down :sunglasses:


(Phil Gorsuch) #17

Second that. Unless I am doing some very aggressive roughing with small footprint parts blue tape and CA glue is the only workholding I use now.


#18

In the absence of an optical comparator, a toolmakers or traveling microscope can be used.

In the absence of any of the above, cut a part and measure. From this, you can derive the actual tool size, to a reasonable precision. This, of course, will be influenced by machine factors, but this is often not a problem, as the derived size you get may be a better match for what the machine will do.


(Richard Cournoyer) #19

Wait, so they inspect your parts using an instrument that you don’t have in the production area? That’s not very smart (or fair). LOL


(Dan Nelson) #20

Incoming parts from vendors, not our final assemblies we assemble from those parts.

Dan