PCB Fabrication via CNC Machine

[canman]

To those of you who make your PCBs with a CNC machine...what kind of bit are you using to engrave the traces? 

I purchased a desktop CNC machine for a different business venture but I just realized I could use it to make PCBs.  I gave it a try with really bad results...I think I went too deep.  But I'm not sure if the bit was incorrect as well.  I've read the little "v" bits are good for PCB engraving but it seems like you'd have to just barely scratch the copper.

I was thinking maybe a 0.5mm router burr bit would work, but the risk of breaking the bit would be pretty high, unless the feed speed was super low.

Any thoughts from CNC users?

[gtudoran]

V-bit is the only way and the engraving depth is based on trial as not all PCB clads are the same.

http://www.ebay.com/itm/10X-Carbide-PCB-board-0-1mm-30-Degree-Engraving-Bits-CNC-Router-Tool-V-shape-/400714167433?hash=item5d4c6cf489:g:sU0AAOSw-vlVkTUm

Isolation routing is nice but, depending on the applications would be much cheaper to use a fab house. Of course for prototyping is quite ok but you will also need drill bits.

Step by step procedure is something like this:
- convert PCB file to CAM file
- define paths is CAM software
- generate Gcode
- insert tool in your machine and let the tip of the tool rest on the PCB surface and tie the chuck
- define the Z position as 0 (zero) in your engraving software
- zero XY axis
- stat the job

Also a nice video: https://www.youtube.com/watch?v=xz4LCIJyd2A

Regards,
DeX

[canman]

I'll have to order some better V bits then...the ones that came with the machine leave the traces extremely rough!  Maybe a diamond coated bit would keep it really smooth..?

[canman]

Turns out the feed speed needs to be fairly slow!  Once I slowed it down, the cuts were extremely smooth and the circuit board looks killer.  Thanks for the help!  If anyone else is wanting to make PCB's without chemicals/etching I'd be happy to help and pass along what I've learned!

[PRR]

> the feed speed needs to be fairly slow!

I think on *any* rotating-tool cutting, you start with the feed just fast enough to finish one "today".

That usually gives a nice cut.

You turn-up feed when you get an order for 10,000 "today!" Making cars was a lot about speeding-up feeds to cut a lot of cast-iron and turn out a lot of cars on existing machinery. But you are not in that situation (yet).

Yes, slow feed can be trouble. My warped table-saw will burn the wood if I feed slow, less if I go fast. But that's poor guidance from bent fence and my un-smooth hands. At the other extreme, high feed rates often demand very beefy spindles and arms to damp the least shake; and of course sharp tough bits.

You don't "need" diamond to cut soft copper or board. You may want carbide (maybe diamond) when you cut a mile of traces and plain-steel cutters go dull too fast for your taste. But unless I am cutting hardened steel or worse, I always start with tool-steel tools, wait until I blunt a few before investing in fancy-stuff edges. (I switched to carbide round-saw blades a long time ago, but I'm still on plain steel chain-saw teeth because I don't blunt that many chains.)

[canman]

The funny thing is, I thought my feed speed before was slow!  My go-to feed speed is 400 (mm, I think...inches would be pretty dang fast) but when I turned it down to 200, the magic happened. 

I don't plan on turning this into any kind of business, as there are plenty of PCB fabrication shops that are very reasonably priced...but it's definitely a game changer for my own personal projects! 

[eva liang]

the pcb shop could drill the hole fastly and accurately with reasonable price.so great

[G. Hoffman]

> the feed speed needs to be fairly slow!

I think on *any* rotating-tool cutting, you start with the feed just fast enough to finish one "today".

OK, I REALLY don't want to right an essay on feeds and speeds right now, but this turns out to be really not true.  The number of factors involved in calculating feeds and speeds properly is...complicated.  Eventually, you hopefully develop some "rules of thumb," but it really is worth while to figure this stuff out properly, if you have a machine which can handle it.  Part of the problem is that, if you run your speeds too slow, you don't really cut, but instead start to scrap away material, which causes excess wear on your bits, and doesn't improve the finish quality.  Your feed speed and your spindle speed really do need to be related to one another to make sure you are getting a good chip.

And while I don't do much PCB work on my CNC, I do a lot of fine engraving, and I really like the bits you can get from Precise Bits.  He also makes some REALLY nice precision collets for the most popular routers/spindles. 


Gabriel

[R.G.]

Machinery's Handbook

[LiLFX]

To those of you who make your PCBs with a CNC machine...what kind of bit are you using to engrave the traces? 

I purchased a desktop CNC machine for a different business venture but I just realized I could use it to make PCBs.  I gave it a try with really bad results...I think I went too deep.  But I'm not sure if the bit was incorrect as well.  I've read the little "v" bits are good for PCB engraving but it seems like you'd have to just barely scratch the copper.

I was thinking maybe a 0.5mm router burr bit would work, but the risk of breaking the bit would be pretty high, unless the feed speed was super low.

Any thoughts from CNC users?

My day job is fabricating PCBs using LPKF cnc machines. I'm running two machines, two plating tanks, and a press for multilayer boards. The bulk of the isolation milling is done with a 8-20 mil 90 degree v-bit from Midwest Circuit Tech. For small areas we use their 4-6 mil 60 degree v-bit. For larger areas of copper removal either a 1mm or 3mm end mill depending on the size of the area. It is super critical to have a completely flat milling surface. LPKF's machines have a depth limiting foot on the end of the spindle that only allows a small portion of the bit to protrude. That makes an uneven surface less critical because the depth limiter rides along the surface of the copper which makes the bit cut at a consistent depth.

I've been wanting to pick up a Shapeoko or X-Carve to try to implement some of the features that LPKF machines are running. Unfortunately, neither Shapeoko or Inventables are interested in working with me. It's unfortunate because I live about 90 minutes from both companies.