Need advice on cnc to pcb circuit job!

[Tenson]

I do it because I CAN and want to do it. Its not a money thing. I do it to prove to myself that I can. A hobby is not all about saving money, sometimes it is proving that you can do it yourself. If it was all about saving money, I would not have any hobbies and simply buy whatever it is. Also, my hobby projects are typically one off types. I have no plans to manufacture a product. So I can go from a board design to finished board ready to populate in less than an hour usually. How quick can you get a turn around on the board (one off) that you want to buy???

Its different strokes for different folks.

My question was actually to the OP who doesn't already have a CNC machine and doesn't have the skills yet. If his goal as set out in the first post is to produce a few PCBs, it will be less expensive and return better quality to use the manufacturer I linked to. £30 will land you a handful of PCBs delivered to your door.

On the other hand, if you are doing this as a hobby then a CNC machine will give you a lot of joy and be highly useful! Alfons37 what is your ultimate goal?

[davegrennan]

alfons, I just thought I'd return here and add a few pointers that I've picked up while taking my first steps into milling PCBs. Hopefully these will save you a few ruined copper boards!
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First level is everything, if your board is not EXACTLY perpendicular you cannot take the really shallow cuts that you would like. Either you will cut too deep in some parts or cut air in others. Set up a touch probe and use something like autoleveller software to level your gcode with your workpiece. It really did the business for me.
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I found that MFD makes a particularly good spoilboard for pcbs. Use double sided tape to hold down the copper board. Using clamps just bends the board! A few strips of tape is strong enough to hold it secure and is easy to get off afterwards.
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Use alignment pins for double sided boards. You just cannot line uop accurately enough just flipping the board by eye, even using marks on the spoilboard.
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Keep in mind that as holes are not plated through you could (likely) have great difficulty in soldering some components, use smd where possible. If you are used to working with commercial grade boards with resist and solder mask etc, its easy to forget this and then realise you cannot actually complete your shiny new cnc made board (happened to me).
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Lastly keep your designs modest and your tracks as fat as possible. Even using 0.1mm V bit, its very difficult to actually cut 0.1mm in copper, expect maybe 0.3mm. I'm sure with more experience it will be possible to get thinner cuts. And keep in mind that the extra cut width will come off your track, so it will be narrower than planned.
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Hope some of this is helpful to you when you do get to finally mill some copper.

[davegrennan]

PS Flatcam is great for turning gerber files into gcode and its free!

[HankMcSpank]

My question was actually to the OP who doesn't already have a CNC machine and doesn't have the skills yet. If his goal as set out in the first post is to produce a few PCBs, it will be less expensive and return better quality to use the manufacturer I linked to. £30 will land you a handful of PCBs delivered to your door.

On the other hand, if you are doing this as a hobby then a CNC machine will give you a lot of joy and be highly useful! Alfons37 what is your ultimate goal?

The reason I used to us a CNC machine to make pcbs was for ultra fast prototyping. I can finish a circuit in eagle & have my board within the hour (vs weeks if using the cheapest chinese fab houses) ...as soon as you have the board, you can start debugging & revision II comes along .....the revision II board can be with me within the hour...rinse repeat.

In short if you are designing circuits, a CNC machine can't be beat for rapid prototyping. Of course once you have your final design...off to the fab house it goes.

FWIW, my design path...

Design board Eagle, then export tracks as gerber & excellon files, then import the gerber/eccellon to do the associated CAM work in Cambam...before finally using CNC-USB to mill the board (CNC-USB has features which are fantastic for pcb milling)

My top tip...find a local signmaker ....checkout their skip...there'll be loads of waste acrylic in there...it's perfectly flat & perfect for use as spoiler.

Even better than ensuring your board is flat ...use probing (which adjusts the Z plane cut depth in sympathy with the boards irregularities (a built in feature with CNC-USB .... https://www.youtube.com/watch?v=0jGY92S8bxM). This method means you don't even need spoiler...my pcb board was always clamped 8mm above my cncmachine's bed...I used tabs to keep the board in place & then just snipped the tabs out at the end.

For double side boards, I used index pins, but again CNC-USB has a feature called 'transformation' which in theory allows you to flip a board over without index pins, the idea is to use a Z mounted webcam to jog to some known coords & then it'll work out the adjustments to ensure your top surface & lower surface are perfectly aligned (this video sort of explains it - https://www.youtube.com/watch?v=JJnenOsbCzU )