Cheap digitizing with aluminum foil and a piece of wire!

[cjjonesarmory]

Just thought I'd share my recent experience. I really needed/wanted to digitize a firearm stock, but costly digitizing probes weren't in the budget, and I don't have the time to make one.

It occured to me that I could make a cheap simple digitizing probe with a simple piece of wire and some aluminum foil. Now this definitely is NOT going to be very accurate, but for my purposes it worked great.

The reason for digitizing the stock was to get the contours of the surface so that I can either A) carve some custom engravings on the stock and/or B) machine a new rough copy of the stock.

So to make the process work, I first took some regular household aluminum foil and wrapped it as tightly as possible around the wood gun stock. I then took a firm foam paint roller and rolled the foil as flat as possible around the stock.

Then I took two pieces of insulated copper wire and stripped off about 1/4" of insulation from the tip one wire, and about 1" on the other. I used a piece of MDF to insulate the foil covered part from the metal table (I have a CNC Mill), and used some wooden hold down clamps to secure the part to the MDF. I sandwiched the wire with the 1" of insulation stripped off between the clamp and part of the aluminum foil where I did not intend to digitize.

The other wire I attached to a simple half-inch piece of round steel with some electrical tape so that the rest of the wire insulation kept any part of the copper wire from touching the steel rod. I mounted the rod in the end of my mill (arbor) with the exposed 1/4" of copper wire pointing downwards.

The wires were then attached to the inputs on the controller that I had configured for the digitizing probe.

Using the Mach3 digitizing wizard (the original Art F. - Z-Axis Digitizing Version) I proceded to do a 1" by 1" square in .050" x .050" (x y) increments. I plan on doing more of the stock when I have time, but for my test I just did 1" x 1".

The resulting triplet file I converted to an STL file using Meshlab. The accuracy is probably not greater than .010" to .020", but for my purpose that was all I needed.

Hope this is useful to someone out there. It got the job done for me. One thing to watch out for, I accidently let one of the leads touch the body of the mill and I saw some very very very small sparking. I suspect that it was the 5V signal wire that touched the mill. I had so quickly disconnected the setup after seeing the sparks that I don't know for sure which wire it was, but I was scared that I had damaged the controllers breakout board, but it seems that no harm was done.

Also keep in mind that the wizard does a square-shaped area and any areas not covered in the foil and electrically attached in some way to the lead will not read properly and could potentially cause damage to the machine if it isn't "smart" enough to stop before it runs into something.

Quick, cheap, dirty, but will work until I build a better probe :-)

[stirling]

Originally Posted by cjjonesarmory Also keep in mind that the wizard does a square-shaped area and any areas not covered in the foil and electrically attached in some way to the lead will not read properly and could potentially cause damage to the machine if it isn't "smart" enough to stop before it runs into something.

Hi. A couple of ways round this perhaps. You could also try covering the top surface of your MDF insulating board with foil. Or more simply if the MDF surface is Z=0 and you use G31 Z0 then there shouldn't be a problem. Also you might want to take a look at my probe routines discussed in http://www.cnczone.com/forums/showthread.php?t=29008 which will eliminate all the (wasted) table probing.

Cheers

Ian