On Friday 06 December 2013 15:28:32 Ron Bean did opine: > >Something that since I have extensive experience with, and the > >destruction one can cause trying to dispose of spent ferric chloride, > >I do NOT want to be involved with ever again. > > The guys here etch PCBs with a mix of muriatic acid and hydrogen > peroxide, which is much easier to deal with. Google "muriatic acid pcb > etching" for more info-- our version is here: > http://milwaukeemakerspace.org/2012/04/pcb-with-lasered-paint-resist-and > -fast-sponge-etching/ > > Note that we're using 30% H2O2 rather than the 2% you typically find at > a pharmacy (I don't know where they buy it). Supposedly you can > "regenerate" the acid mix by bubbling air through it, but we've never > gotten that to work, so we just mix up a new batch each time. > > Instead of photo resist, we use black spray paint, and etch the paint > away with a laser cutter. > > We've tried cutting circuit boards with a CNC engraving machine, with > varying results. The main problem seems to be keeping the board > absolutely flat-- it tends to warp, and then you don't get a consistent > depth of cut. There is a method of "height mapping" the board ahead of > time, and using the computer to compensate while engraving. I don't know > the details, but it does seem to work. I think it's a plug-in for Mach3. > Very careful mounting might also work. > I machine an insulating pallet out of micarta, which doesn't require mapping if the pallet is clean, and the top etch is deburred on a sheet of 600 wet-r-dry, wet with cuting oil before turning it over. I use flat head 0-80 screws threaded into the micarta as hold downs so they "wedge" the board in place, so that there is just enough tension to keep it from walking around a thou or so if the bit gets really dull. The use of tape allows just enough sideways wiggle that I can see it in the etching of a pad. The insulated pallet allows me to establish the z depth with a G38.2 directly from the tip of the etching tool and some follow up code to modify either G55 for the top, or G56 for the bottom. I haven't felt the need to do a preliminary mapping grid run since I found that 5 seconds on the wet wet-r-dry stuck to a granite surface slab, and a decent blow from the air hose to clean it up again took care of the z depth problems.
Now with the camera mounted and working with camview-emc, and the align.zip also working and making some hold downs out of 1/2" micarta, one with a contact for the probe connection in its tip, I might be able to do away with the pallet, but haven't made the micarta hold downs yet. On my todo list though. So is installing a few sheets of 2" R11 styro between the studs to ease the electric bill for heating that garden barn/shed. I have 4 sheets of it blocking the garage now. But here in WV, its plumb fugly outside, which is where I'd have to cut the styrofoam. Upper 30's F, and pouring it out of some pretty tall boots. Toss in enough wind & me and my diabetic feet are gonna 'stay in the barn' & try to keep warm. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> "Nature is very un-American. Nature never hurries." -- William George Jordan A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Sponsored by Intel(R) XDK Develop, test and display web and hybrid apps with a single code base. Download it for free now! http://pubads.g.doubleclick.net/gampad/clk?id=111408631&iu=/4140/ostg.clktrk _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
