I think I’ll need 2 different boards about 20x15 cm each and 5 small once 30x30 mm each. So in this case home made PCB is my only option as ordering them will be too expensive.
I did made my own PCBs at home many, many times. I used many different methods, I had most success using photoresist film and Presensitized boards, but I never try ti mill PCB on a CNC before.
accuracy of your CNC becomes critical. The biggest determinant of how precise your track spacing can be is total runout of the machine. That also needs to take into account the precision of your mill bit and the flatness of your copper sheet, as unless you’re using end mills (expensive) you’re likely to use a tapered bit, meaning as you penetrate the copper further to get good clearance across the entire board, you will have a wider gap between tracks. See http://phk.freebsd.dk/CncPcb/calibrate.html for some good pointers on testing this
Currently the machine has 200 step per mm so the resolution should be 0.005 mm (untested). I already got some precision mill bits 0.3mm to 1.2 mm.
Flatness level… I’m working on the auto leveling code.
Runout is not a measure of theoretical accuracy, and has many other factors other than step size For example, if you don’t have perfectly aligned spindle, you increase runout (elliptical tool path). And if you don’t take care when locking the tool in the collet, you can get more runout. The best way to prove this is to go through the process of testing with the test pattern I shared earlier, it’s a good way to measure actual performance.
Do you by any chance have a g-code already generated for this test?
I don’t, and I’m kinda remote at the moment (I’m in Seattle USA this week, and my Eagle + PCB-Gcode laptop is in Sydney AU) so I can’t even offer to run it off for you. I will try to do that next week unless someone else can create the board in Eagle from the scripts and run PCB-Gcode over it earlier?
@ EvoMotors -
Yes, I an doing wire wrapping for more that 30 years, and I still build a wire-wrap board to check out a new circuit before I commit to PCB for my customers.
The question was specific about milling PCBs, not about prototyping in general.
FWIW, we have used http://www.pcbcart.com for over 10 years now. Never once had a issue with any of their boards.
I punched in your board size and the cost was $80 + shipping to get 5. The minimum is 5 boards when using the Prototype PCB service.
If you use the Standard PCB service to get 1, it was $101.95 + shipping.
@ VersaModule -
Even $80 for a prototype is too much. I may need 2 or 3 versions before it will be final.
No one else make mistakes around here?
no-one makes mistakes on 20cm boards, no
Lots of people make mistakes on 10cm x 5cm boards.
@ EvoMotors - Since we’re on this topic, would you spend $3K on a machine that could help you produce those prototypes for $10 dollars? If the prototype is important to you then you’ve got to be willing to put out for it.
Who said anything about spending $3K?
@ EvoMotors - i did; just now.
Do you think 3K is the minimum?
@ EvoMotors - I do.
@ Mr. John Smith -
I don’t know where you got this 3K number.
This weekend I’ll probably try to mill sample PCB on my 3D printed CNC machine with NETMF controller. I did not spent remotely 3K on it, but I think it’s going to work.
3K is probably about right for a base model LPKF machine.
But you can probably acheive similar results with a ebay CNC3020 for about 1/10th that.
$3K is about the cost for an Othermill which is highly regarded right now as an excellent personal desktop mill. You can and many others have certainly built their own machines much less than that. But $3K sounds about right for a low end (not Chinese) desktop mill that you might purchase.