3D touch probe

Hi all,

I am in the process of prototyping several tools, and realized life would be so much easier if I had a touch probe to find hole centers, accurately setup material, etc. in particular for CNC machining multiple parts.

So, I searched cnczone and googled, but could not find many affordable (<= 100$) 3D touchprobes that both look to be really well made and accurate enough (<0.01mm). Thus I decided to make my own :-) It will be based on a conventional ball bearing and spring loaded pin/tip, classic system.
I already designed the printed circuit board and I am waiting for the PCB fab to send them. It will have an internal schmitt trigger circuit to reduce noise and bounce effects, and an LED to signal contact. Center point will be adjustable in order to reduce runout.

I have most materials on hand and what I did not have, I found suppliers for. I have a good supplier for the probe body, which will be a nice steel "can" and shaft. The probe will be ruby ball (5mm) tipped, M4 thread, 30mm long. Since I had to order the circuit board and electronic/electrical components in quantities bigger than 1, I was wondering if anybody would be interested in purchasing one of those probes ? I think I could sell those between $80 and $120, depending on how many units of certain parts I can get. Maybe even cheaper.

I am just gaging potential interest... If there seems to be a need, I will produce a batch.

As soon as I get the first probe assembled, I will publish pictures and do some precision and repeatability measurements.

So, anybody with interest, let me know and I will make sure to keep you in the loop.

Cheers !

Yep...

Yes I would be interested - any pics yet

Yes.

Hi,

Thanks for replying to my post.

I am currently still waiting on the circuit boards to come back from the manufacturer. I received the electronic components...
I will post pictures once the first probe is assembled, hopefully at most in a couple weeks.

Hi
I will be interested in following your project. I started to build one myself but as you know it still in the bucket waiting for me to get back to it. Ended up mounting a camera on the side of the head and use that to zero in on jobs This is good for xy positioning only and not for measuring.
What voltage are you running across you ball bearing as I was concerned about arcing across the contacts?
Will it have a out put signal as well as the LED?

Wishing the best for this project

Russell

I am using 5V, no arcing there. The probe will have 3 wires: ground, 5V power, digital output. It uses a schmitt trigger to avoid switch bounces.

Quote:

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Originally Posted by rusel

Hi
I will be interested in following your project. I started to build one myself but as you know it still in the bucket waiting for me to get back to it. Ended up mounting a camera on the side of the head and use that to zero in on jobs This is good for xy positioning only and not for measuring.
What voltage are you running across you ball bearing as I was concerned about arcing across the contacts?
Will it have a out put signal as well as the LED?

Wishing the best for this project

Russell

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Yup!
Put me down for one!
Bill

would definitely be interested in one

can't wait to see what you've some up with

I received the printed circuit boards. I got the nice ENIG ones, a bit more expensive than standard. Gold plated, excellent planarity, much better than tinned PCBs. I immediately noticed a mistake I made. No big deal, just a hole that is too big, I can work around it. I fixed the design and will reorder if the first probe turns out ok.

Still waiting on a couple electronic components as some of the resistors I got had the wrong footprint. Stupid me I got the 1206-size SMT resistors that are sideways...

I worked on the gcode for machining the base which will hold the PCB. I am going to test making a mold so I can replicate it out of epoxy loaded with a filler.

I made a test holder plate from MDF, just to verify dimensions and fit. Attached a couple pictures of some of the parts: test MDF PCB holder, Steel body, PCBs
The PCB holder holds the PCB on top of 3 pointy cone-ended M3 set screws. The hole with a notch is for the cable to come out of the probe.
The PCBs sit on top of each other with three 5mm steel balls sitting in the bigger holes. This is a design similar to http://www.cnczone.com/forums/digiti...ouchprobe.html, however there are several improvements. I am hoping with the more precise PCB, higher flatness of the ENIG process and generally more precise and rigid parts, it should get within 0.001" repeatability. After I get the rest of the parts and test the probe, I will try doubling the PCBs thickness to increase rigidity even further. We'll see if it makes a difference.

Attachment 181689
Attachment 181690
Attachment 181691
Attachment 181692

Yes I am interested

I made another test base out of MDF. This fixes the hole for the LED, and the slot and hole for the cable. I added blind holes to hold the spring that will press the PCB on the set screws. I received the pointy set screws, this will work great... Still waiting on a couple SMD resistors. Once I get those I will assemble a PCB and test it.

I am interested. Have you put any thought in to the "next phase" of putting the probe on an arm with encoders at each joint, and being able to digitize like a Faro arm?

At this time I just thought about building a probe that is useful for a CNC mill or gantry in order to locate and setup material or parts. It could be used for digitizing, but I think there are better ways to digitize objects (optically).

The problem with the arm with encoders is that the encoders have to be exceedingly precise, even more so if the arm is going to be any significant length, and the joints have to be really tight with absolutely no backlash. That would be yet another project.

Maybe once I get the probe working satisfactorily, I will think about an arm for it :-)

Quote:

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Originally Posted by mcphill

I am interested. Have you put any thought in to the "next phase" of putting the probe on an arm with encoders at each joint, and being able to digitize like a Faro arm?

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Still interested, have you made any progress on this :)

Hey, yes, but I got sidetracked on other projects (like fitting proper homing switches to my mill after I crashed the head...). I am currently waiting on revision 2 of the printed circuit board to come back from the PCB shop.

Quote:

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Originally Posted by johnsattuk

Still interested, have you made any progress on this :)

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:wave:

Definately interet here


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