next topic »

[on:]

Hi there,
I am an engineering student at the University of Cape Town. I have access to a pretty old PCB etching machine, the type that simply mills away copper to leave the tracks. I was wondering if anyone has tried to produce their own Arduino Mega and if so do you have any advice?

I am hoping to simply take the Eagle CAD .brd file and get an Arduino Mega board made. I currently have the mega1280 and am really happy with its's performance. I am using it in a electromyographically controlled prosthetic human hand and am looking to use this board again in a similar project.

Many thanks for any help or comments!

[Reply #1 on:]

That's a prototype machine. I've read about it but never used one. It works as a mill, that's right, taking away unwanted copper. What's the capability of your machine? Say, what is the size of the smallest milling/routing bit? I just measured the mega2560 PCB file to have 0.3mm spacing between the wires that come out of the atmega chip. If you have a 0.3mm diameter bit, you might be able to do it. Sounds challanging. I've never seen such small bit in a regular machine shop.

I'd like to see someone say yeah, I did it with a prototype machine. Always good to know what one can do with such a tool.

[Reply #2 on:]

I have a milling machine (an LPKF.)  It's basically hopeless for a MEGA-class board:

1) Without "very expensive" bits, the typical quoted limit is 0.2mm routes.  But that requires very careful adjustment.  And while the Mega may have 0.3mm between tracks, the ATmega2560 itself only has about 0.15mm between the SMT pads...

2) You don't get "plated through" holes, which means you have to solder on the side that has traces (both sides if both sides have traces), and put wires in all the vias (144 vias on Mega!)  This is also somewhat impossible on some components (connectors.)

[Reply #3 on:]

Thanks for your comments guys. Ya the main deterant I guess is soldering up all those vias! I really want to create my own Arduino board and I've been very happy with the 1280 chip, I like having the capacity that it offers, especially with 16 ADC channels. OK well I might give it a shot and I'll let you know how it turns out!

[Reply #4 on:]

There are ATMEGA1280 breakout boards available, which makes it a trough-hole version.

[Reply #5 on:]

westfw,

I've seen the word "LPKF" before. How much is a machine like that?

[Reply #6 on:]

About $10k for the base units, new.  I got mine used on eBay for much less; they show up periodically.  It'll also cut complex shapes out of FR4 fiberglass, which was part of the idea, but I think they are increasingly "silly" as professional fabrications becomes easier and cheaper...

[Reply #7 on:]

westfw,

These things can cut holes on enclosures, right? Might be another revenue of income if they can. Currently I'm using a dremel. Very awkward and inaccurate and sometime dangerous. I wish I had a mill.

[Reply #8 on:]

These things can cut holes on enclosures

If you have a flat panel that you need cut.  The total Z-axis range of a dedicated PCB mill is about 1cm...

[Reply #9 on:]

More specific complaining: at the time I bought the LPKF, I was interested producing small numbers of very small and quite experimental boards, because even the fabricators willing to deal with hobbyists generally had a minimum charge of $50 or so.  (for which you'd get something like 3 boards each 80x100mm.)  That was a pretty reasonable price, except that I had little interest in spending $50 for 50 copies of a 20x25mm board that didn't work :-(

Since that time, the "co-op" services like batchpcb and  dorkbotpbx have appeared  and seem to do a pretty good job of handling that market segment...

[Reply #10 on:]

Like one of these on ebay?

http://cgi.ebay.com/T-Tech-Quick-Circuit-Complete-PCB-Prototyping-CNC-LPKF-/320488544878?pt=LH_DefaultDomain_0&hash=item4a9e9b1a6e

Considering each motorized degree of freedom will cost $1,000 (scientific quality), this price is within reasonable range but still too much for me. Anything cheaper? Just a CNC? I know there's a makerbot but I don't have patience to build one.