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Old 21st February 2013, 07:55 AM   #1
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Location: Perth, Western Australia
Default SSTART Pcb and power supply project - CNC Routing

Hi all,
I've recently finished building a small CNC router, and intend to use it to mill pcbs. There is of course quite a few steps in between knowing it can be done and achieving the goal, so this thread is intended to explore the process of learning to use the thing and producing some pcbs that I can actually use. As such I thought I'd pick something relatively simple to build and work through all the steps along the way. I should emphasize that I'm a learner at all of these things so this will serve as a documentation of my mistakes along the way I suspect...

The planned project - the SSTART Preamp and a as yet to be determined power supply - I'm thinking something based on the psu described in the BOSOZ though at the moment
The SSTART Preamplifier Why on earth would anyone do such a thing? Article By Grey Rollins
http://www.firstwatt.com/pdf/art_bosoz.pdf

I intend to design a stereo pcb in eagle, then use
Welcome to PCBGCODE to generate the Gcode

the cnc router is a Shapeoko with a few little mods
Shapeoko | Precision by DefaultShapeoko | Precision by Default

using mach3 to drive the CNC router
ArtSoft USA - Home of Mach3 and LazyCam

And possibly using Mastercam to refine the Gcode
Mastercam CAD/CAM software

I'll do my best to detail what I accomplish along the way and we'll see how it goes.

Music to work to today - Cake - Comfort Eagle

Last edited by aspringv; 25th February 2013 at 12:20 PM. Reason: Clarity, and thought it would be amusing...
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Old 21st February 2013, 08:04 AM   #2
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Default CNC Router

The router in question
https://picasaweb.google.com/lh/phot...eat=directlink
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Old 21st February 2013, 09:52 AM   #3
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Default first pass at pcb

First spin at PCB.

I am no layout expert so please, constructive comments welcome.
Parts are not as labeled - nor are values as yet. I used roughly equivalent parts from the eagle library and I'll alter labels/values accordingly once it's nailed down.

I also will need to alter the design rules to better accommodate what the router will need to do to cut the pcb out. There are a variety of pads connected with cross shapes to traces - the mill cannot do those cuts (nor are they necessary).

I also have two placeholder parts until I find a spade connector part in the eagle library... these are for the 60V supply connections (labeled X1 and X2 for now)

Next Power Supply layout...
Attached Images
File Type: png PCB v1.png (258.8 KB, 363 views)
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Old 21st February 2013, 12:30 PM   #4
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Default first pass at power supply pcb

Copied from the design of the BOSOZ article by Nelson Pass (thank you sir!).

I'm using a pile of 5mm leds at the 63V reference due to the fact that I'm looking at about of 1000 of them right now... And the same caveats apply as the previous pcb, in that I've used what I think is an appropriate substitute part and will label values as needed later on should the basic layout be sound.

Music whilst doing this - CCR
Attached Images
File Type: png Power PCB v1.png (154.9 KB, 347 views)
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Old 24th February 2013, 10:33 AM   #5
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Default PCB vLots

Lots of refining and i saw a few errors from the first pass. included the 5W resistor and refined a few of the isolation settings needed to mill it.
Attached Images
File Type: png SStart PCB v5.png (262.3 KB, 325 views)
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Old 25th February 2013, 12:53 AM   #6
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I'm a little vague what stock you are using to make the PWB. Are you milling off the copper of copperclad board? One sided or two sided? I thought one had to use photoresist and a FeCl chemical to do this.
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Old 25th February 2013, 02:09 AM   #7
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Default Stock to be used

I'll be using single sided copper clad pcb materiel. The PCB-Gcode outputs code for a two sided pcb if required but I thought I'd start gently. The point of this is quick and easy creation of pcbs without using FeCl and similar. Basically by the end of this I hope to just be able to throw some pcb materiel in the cnc machine and get a finished job out the other side.
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Old 25th February 2013, 05:42 AM   #8
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Default Tweaking settings

Setting up pcb-gcode to output something useful for my machine has been a little tricky.

For one, I intend to use a 1mm flat end bit to do the milling, and all the faq's I've read are oriented towards using an engraving bit (pointy). I have some .25mm bit's, but it doesn't seem worth it for a pcb thats all through hole parts, and where all the traces and pads can be made to be 1mm away from each other.

That was the next trick - setting up the design rules in Eagle to keep everything at least 1mm apart. Finding where to set pad sizes took a while, but I seem to have a setup that works now. As well as isolating the ground plane by 1.5mm, that seems to be the trick. Below is the output from pcb-gcode and from a cnc simulator (So I have an idea of what the hell the gcode actually represents)
Attached Images
File Type: png SStart PCB gcode output.png (254.1 KB, 297 views)
File Type: png SStart PCB simulated.png (345.4 KB, 287 views)
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Old 25th February 2013, 03:45 PM   #9
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Well, cool. Let us know if the milling works, I've never heard of this. I detest FeCl, and have too much pride to pour it down the drain when it is used up. Hazwaste disposal is >$400 a 55 gal drum, not a service a diyer can use. I had heard you could etch PWB's with a mixture of HCl and strong peroxide, about the time Al Kaida started using peroxide to try to **** up airplanes. So peroxide disappeared from all the store haircare shelves, and HCl is out of fashion now as a pool cleaner, also. Best I can find without a hazmat UPS shipment is 6% HCl in Lysol for cleaning toilets (mixed with detergent).
Incidently, the phrase "PCB" is a bit out of fashion here, where they spent $xxxxxxxxx digging up the part of Bloomington where Westinghouse used to make capacitors with the chemical of the same name. Hammond started calling them "PWB"s for printed wire board.
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Last edited by indianajo; 25th February 2013 at 03:51 PM.
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Old 26th February 2013, 01:42 AM   #10
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Peroxide banned? I remember doing etching at high school with that mix... I would have been 16? Hilarious to think that would make me a terrorist suspect these days

I also had a few issues sourcing chemicals at some point. I had a quick look around to see if I could get some HNO3 and H2SO4 for doing some home anodizing, and the best luck I had was a lab chemical supplier. Admittedly, I'd have to drive about 2.5 hours to pick up but it's not completely unavailable.

I believe that HCl is also used in making Meth so I'm not sure you just have Al Qaeda to blame there...

I just realised that having googled a few things whilst writing this post that I'd now appear to be a drug manufacturing terrorist to whatever govt agencies track these things

I'll be sparking up the Router today to try my first run at milling a pcb - I'm not expecting much as I've made it a one pass cut but we'll have to see.
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