Ever make Xmas ornaments out of PCB's?

[Kev Williams]

I never did until today! Don't think I'll be making any more soon, either! This was tool work, not laser...

One of my customer's engineers asked me last week if I could make some ornaments out of some large 350x450mm PCB's they had to destroy? --He asked me "is this even possible with 1.6mm FR4+copper?"

Oh, I don't see why not! ... but it didn't take me long to figure out why he asked that question...

What he wanted was for me to turn this:

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into THIS. He even sent me the vector file, it was laid out perfect to miss all the large mounting holes...

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As you can see, I did get the job done, but wow...

I put the plate on my trusty IS7000, set my 3-flute Garr 1/16" endmill to the correct depth, and proceeded to drill the hanger holes.
No problem. Let's try a tree...

No problem! Cut nicely-- Let's try another one...

Halfway thru the second tree, the copper started mushing up the edges of the cut, and I noticed the spindle was rising up--
I stop the machine, and the endmill was so dull already that it wouldn't cut the copper, and the lower layer of copper was
balling up... Well, that endmill had about about 50 hours of cutting holes in black anodized aluminum on it, so I grab a new
2-flute endmill...

It cut the first tree dandy. About 2/3 thru the second tree, it got so dull that it wouldn't cut as fast as the machine was
pushing it, and it snapped in half...

It was then that I looked up "FR4 PCB"... 8 layers of fiberglass with 2 layers of copper top & bottom. That might explain it!

So to finish this job I ended up cutting them out with a standard engraving tool, with a 12° angle and a .020" or so tip.
I could only go .015" deep at a time, and 8 trees was about it before having to sharpen the tool.

I've never seen anything dull a carbide tool like this stuff did! The tool wear was probably at least 2x the wear I get cutting the
same linear inches of stainless steel!

Each pass took 45 seconds from tree to tree, 4 passes each tree = 3 minutes each, x30 trees = 90 minutes pure machine time...
plus around 10 tool sharpenings, add at least another half hour, plus deburring, plus two $9 endmills...

They turned out really nice, but I'm not sure I want to mess with cutting this stuff again!

[Richard Rumancik]

Yes, it is amazing how fast fiberglass can dull a sharp edge or tool. The copper itself is no problem; it is the glass. I would probably try waterjet to do something like this.

[Matt McCoy]

Awesome! Cool idea.

[David Somers]

Kev,

Have you tried a Chip Breaker or a diamond cut router bit for use on PCB's? The diamond cut is not actually diamond. It refers to the flute pattern. The diamond cuts slower but cleaner and is supposed to last longer. The Chip Breaker cuts faster but not as smooth a finish, though I understand it is still a reasonable finish. It doesnt last as long as the diamond cut and isnt the preferred bit for industrial use. They are both pretty good and both are used in manufacturing so they should last a good while. You can get them in up and down cut as needed. I believe Amana has the designs to give you a starting point.

I am not experienced with these btw. I had a friend who has asked about cutting this stuff and I had looked up the bits needed. We haven't decided to play yet.

Hope that helps!

Dave

[Kev Williams]

I cut holes in a few fiberglass Hoffman electric box every week, but they're basically an epoxy/silica powder mix, 1/8" thick. I cut them dry with the same Garr endmills, each box has roughly 40" linear inches of hole cutting, and I can get about 30 boxes out of an endmill before it's too dull to cut decent. This stuff took out a brand new endmill in less than 30"!

I just pulled the tool that cut the last 8 trees, and it only cut the last .015" of depth (out of .062") , plus about .005" to be sure it cut clear thru...

The tool is a nearly-gone 1/4" shank with carbide tip, edge ground at 35° with only a 12° taper. Because the tool is tapered, the entire cut edge was cutting material, but in measuring a .012 angle x .020" deep, math says the amount of material being cut was only .0043". Using Corel to help, I came up with around 9 or 10 linear inches of cut, x 8 trees, so roughly 80 total linear inches of removing only .005" of material. Also, I flood all my cutting with a light mix of TrimSol machining fluid...

Here's pics of the tool as best as I could take- both are the same pic, I just added a straightline to highlight the tool wear...

You can clearly see the serrations in the cutting edge, caused by each layer of glass. I have NEVER seen carbide wear this badly, with what I consider a small amount of work! With 8 layers of glass within .062", that comes to each serration being around .008" apart, and the depth of the serrations is about half that distance! That's a LOT of missing carbide!

Some of the available diamond-cut and other 'roughing' tools might make shorter work of cutting this stuff, but I have to agree that a water jet is probably the best way!


http://www.engraver1.com/erase2/tool1.jpg

http://www.engraver1.com/erase2/tool2.jpg

[Glen Monaghan]

Here are a few I made from old circuit boards. I tried to let the trace patterns guide the ornament design. Cutting was done with jig saw, wearing out a number of narrow, fine-toothed blades in the process.
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