Hi Peter - the board takes about 20 minutes to mill out. You have to be careful how you draw the board in AutoCAD, because it will mill the board in the same order. I look for the longest continous line I can do first, then the second, etc. I have not tried to remove copper from a large area (except under an antenna, receiver & transmitter I am working on for another project). How much you can remove in a single pass depends on the diameter of the end mill. If you wanted to take the time to program out large open areas to remove with an larger diameter end mill and then progressively smaller areas with a smaller end mill - it could be done - however I feel the time to draw out the path's would be very time consuming. I tend to run the end mill on that board a 2 inches/minute. The engraving tool I run at .5 inches/minute. The engraving tools tend to wear out quickly - so I use them only when I need super fine pitch. The .029" end mill has produced about 20 boards and shows no sign of wear at this point. Kind regards, David David V. Fansler s/v Annabelle dfansler@dv-fansler.com www.dv-fansler.com -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Peter Restall Sent: Monday, March 01, 2010 2:20 PM To: piclist@mit.edu Subject: RE: [EE] PCB etching experience Evening David, How long does it take to do a board that sort of size (roughly - obviously it depends on track complexity) ? Is it comparable in speed to chemical etching ? I noticed you've milled just the gaps between tracks; have you tried to take larger areas of copper off the board at any point - just etching the gaps between tracks seems to be common on the CNC boards I've seen on the web, but I personally don't like to leave floating copper. I'm just wondering if it's too much hassle to do this (ie. takes too long) ? How long do you reckon the tools will last before needing to be replaced/sharpened ? Cheers, Pete Restall --- Original Message --- I built a CNC machine from a milling machine using EMC2 software and an interface of my own design. While I did this orginially to do aluminum with, I recently have been doing PCBs with it. For one board that uses a 2mm x 2mm chip with 3 pins on opposite sides I use a 20 degree engraving bit for a gap of about .018". For less critical work I use a .029" end mill set only deep enough to remove the copper and not the board. You can see a board I am currently selling at http://www.dv-fansler.com/dvf%20Technologies/lx200_keypad_sim.htm along with 3 pictures. This board was done with the .029" end mill. I have done over 20 boards on the same end mill and they still look like the first one. BTW - I do my layout in AutoCAD and then convert it to ngc with a free lisp program called Realize. David David V. Fansler s/v Annabelle dfansler@dv-fansler.com www.dv-fansler.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist