Hello Guest it is October 18, 2019, 10:22:00 AM

Author Topic: Digitizing probe  (Read 35859 times)

0 Members and 1 Guest are viewing this topic.

Offline zarzul

*
  •  317 317
  • Wyoming, USA
    • View Profile
Digitizing probe
« on: October 24, 2007, 01:31:32 PM »
I have just got my design version of a digitizing probe finished ready for the testing stage. 
It has been an interesting project. 
I still have to make a stylus for it but for now I will just use a allen head screw. 

I intend to try a production run of 10 of these and hope to keep the price down where my fellow hobbiest can afford these. 

I am looking for feedback on how to perform sensitivity, accuracy, and repeatability testing on this.

The probe body is made from 3 pieces, top cap, shell & bottom cap, these all screw together.

The electrical grid is made from a blank pc board with balls soldered on it.  The grid is attached to the bottom cap with several spots of RTV about 1/8" thick.
It's plane is adjustable through 3 set screws coming up through the bottom of the cap, these will deflect the grid a small amount for centering the alignment.

The rest of the contact is through the movable piece, not sure what it should be called.  It is made from plexiglass with brass rods for the contactors.

The shaft is a hardened steel shaft screwed into the top cap.

I deleted most of the pictures since the design has been refined. 

On the last post the first picture shows the assembly with a aluminum piece holding the brass rods,  this is just an alignment device used to hold the circuit board in place while the RTV cures.
« Last Edit: December 03, 2007, 02:14:26 PM by zarzul »
Re: Digitizing probe
« Reply #1 on: October 24, 2007, 01:44:34 PM »
This is looking very cool.  Definitely interested - Just don't know how much I would be willing to pay at this point.  Will watch for future developments and improvements.

Bob @ BobsShop

Offline zarzul

*
  •  317 317
  • Wyoming, USA
    • View Profile
Re: Digitizing probe
« Reply #2 on: December 03, 2007, 02:09:54 PM »
Well I got some changes made to the probe design.  The attached pictures show some of the internals and the finished product with relative size.

Note the LED, it lights up when the probe touches an object.

I have now put an ad on bargain basment for these for those interested.  It is all machined using mach3 mill and lathe.

Arnie
Re: Digitizing probe
« Reply #3 on: December 03, 2007, 02:54:06 PM »
Very nice work!  Does the probe react to non-conductive objects?  Or, just metal.

Bob @ BobsShop

Offline zarzul

*
  •  317 317
  • Wyoming, USA
    • View Profile
Re: Digitizing probe
« Reply #4 on: December 04, 2007, 02:32:37 PM »
Bob,

This might be a double reply to your question.  I must have sent it to you on a pm already. 

It probes both types of objects,  the probe doesn't rely on electrical contact with the object, just mechanical contact.   It sends a open contact signal to Mach3 to trigger the probe input and lights up the LED.

It actuates in the x y & z directions.  Repeatability has been excellent,  the centering of the stylus works well but it takes a steady hand to calibrate,  I have been using an indicator on it mounted in the spindle, then rotate the spindle by hand and adjust the screws until the runout on the ball tip is 0.0005.  My indicator doesn't read much better than that.

Arnie

ynneb

*
Re: Digitizing probe
« Reply #5 on: December 08, 2007, 04:41:30 AM »
Looks great.
I guess the voltage is low across the contacts, otherwise it might arc and give a false reading? Also because the circuit is divided across 3 contacts equal distance from each other, does this give different results depending on direction variations?
What speed do you do the digitizing?

Offline zarzul

*
  •  317 317
  • Wyoming, USA
    • View Profile
Re: Digitizing probe
« Reply #6 on: December 09, 2007, 01:58:57 PM »
I have been using the find "find center of hole"  on the pull down menu from Mach.  Also the wizard that Art made, the bed of nails approach.  I didn't realize I could change the speed but I would guess is is running at about 8"/min.  I will check later today.  The LED just lights from the parallel port breakout board, that uses 5volts for sensing voltage on the contacts.   

I am not sure about the different direction response.  One of the tests I do after centering the probe using a dial indicator on the ball point, I rotate the probe in the spindle and fine tune the centering adjusting screws.  I get it down to .001 runout or less.  Then I do the "find center of hole" routine a couple of times, it comes back repeating from .0006 to .0000 each time,  then I rotate the spindle 180 deg and run it again.  This time it comes back at .003 on the x and .002 on the y.  A small amount .001 or so would be the centering adjustment.  The remainder would be the difference in actuation direction. 

I think that it is pretty good, it can't compete with the precision of a Renishaw, but not everyone has that kind of money to spend.
Re: Digitizing probe
« Reply #7 on: June 25, 2017, 10:44:39 PM »
I have been using the find "find center of hole"  on the pull down menu from Mach.  Also the wizard that Art made, the bed of nails approach.  I didn't realize I could change the speed but I would guess is is running at about 8"/min.  I will check later today.  The LED just lights from the parallel port breakout board, that uses 5volts for sensing voltage on the contacts.   

I am not sure about the different direction response.  One of the tests I do after centering the probe using a dial indicator on the ball point, I rotate the probe in the spindle and fine tune the centering adjusting screws.  I get it down to .001 runout or less.  Then I do the "find center of hole" routine a couple of times, it comes back repeating from .0006 to .0000 each time,  then I rotate the spindle 180 deg and run it again.  This time it comes back at .003 on the x and .002 on the y.  A small amount .001 or so would be the centering adjustment.  The remainder would be the difference in actuation direction. 

I think that it is pretty good, it can't compete with the precision of a Renishaw, but not everyone has that kind of money to spend.

this is old now but what is the status if any
thank you

Offline zarzul

*
  •  317 317
  • Wyoming, USA
    • View Profile
Re: Digitizing probe
« Reply #8 on: June 26, 2017, 09:38:42 AM »
These are available from CNC4PC.com
Re: Digitizing probe
« Reply #9 on: December 31, 2017, 02:26:18 PM »
I'm inquiring about this on that sight....is software included? is there a plug in for mach 3? just trying to get into digitizing and doing some shopping around
thanks