At my age, it is projects like this that make me want to get up in the morning and do something instead of sitting around the house all day. I like staying home and putzing around in the shop or dreaming up new projects.Art
AKA Country Bubba
(Older than Dirt)
I built my first cnc for the very same reason as alfons37. Took me a while to even get as far as trying to route a pcb. You gotta learn how to cnc before you start on a pcb. Then theres the added complication of levelling, alignment pins for double sided etc pretty soon it all gets pretty darn hard. Prepare to destroy a load of copper boards. You gotta keep in mind when designing the boards that you can expect to route 0.1mm gaps easily so you need to keep your pcb design modest.
To get to the op's question, the machine you need will need to be super precise but not necessarily super strong, if knocking a few microns of copper off the top of a board is all the stress it will get. The chinese machines may well do the job, but you cannot be sure of what you are going to get with one of these. However given your budget, your choice is a cheap chinese machine or none at all.
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Last edited by eurikain; 19-10-2015 at 02:22 PM.
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?
Last edited by Tenson; 19-10-2015 at 01:59 PM.
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!
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.
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.
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.
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).
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.
Hope some of this is helpful to you when you do get to finally mill some copper.
Last edited by davegrennan; 23-10-2015 at 02:09 PM.
PS Flatcam is great for turning gerber files into gcode and its free!
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 )
Last edited by HankMcSpank; 23-10-2015 at 10:03 PM. Reason: Particularly Mary Hinge.
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