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Messages - ktownsend

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Thanks to both of you for the very thorough replies.  Obviously I'm utterly new to this, but I definately don't mind doing some reading.  If you can tolerate just a bit more spoon feeding, though, would either of you be able to suggest a metal alloy that would be easy to work with (i.e., soft) when starting out?  I'm not terribly worried about longevity, etc.  I really just want to get to know the software and the machine, and have something thin I can easily cut and experiment with.

And just to clarify (Simpson), what I want is to actually cut right through the material.  I need a piece of metal with precisely positioned 'holes', and I spread some solder paste across the surface of the metal with a squegee, leaving paste in the holes.  Here is an example (though cut with a laser):

http://www.gsiglasers.com/UserFiles/Images/Market%20Sectors/Electronics/precision_cutting.jpg

Kevin.

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Rich:

Thanks for the reply.  I have the metal pretty securely bolted to the base (to keep it flat), with some thick paper underneath to absorb any cutting past the metal (I have the Z limit on Mach3 set to -1.0mm ... great feature since I have no hardware limiters).  The holes are very small.  As small as 0.2mm for a 0.5mm pitch QFP footprint, for example.  Typically, the holes are more like 0.05" though.  I had no problem removing the copper layer from a sheet of FR4 with the same setup (though the copper was very thin), which is why I was surprised the aluminum wouldn't cut.  As per your advice, the spindle is quite high speed (25K RPM I think).  And I tried a 0.2mm endmill ... it broke as soon as it came in contact with the metal. :-(

I had hoped it was as simple as changing the bit, but reading your comments it seems not.  Can you recommend a brand/type of cutting fluid to try, or at least some characteristics to look for?  Given that I'm completely new to this, I'd rather trust someone elses judgement?  I'm sure I can find 100 recommendations on the web, but I may as well start with one that works with someone competent, and see how that works out.

Kevin.

PS: I've attached a photo just in case it help with any diagnosis, if anyone is willing to take a look.

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I've been trying to learn the ins and outs of CNC routing and Mach3 (I just bought a license last night), and have been trying to mill a 0.02"/0.5mm sheet of anodized aluminum.  I've tried a 45°/'V' 3.17mm carbide bit that worked well on a piece of copper clad FR4, but it absolutely won't go more than about 0.1-0.2mm into the aluminum even if I put the z-depth on the cut to -1.0mm or higher, for example.  When I try to move the bit down manually (with the spindle on of course), it just won't 'enter' the metal.  I also tried a 0.2mm drill bit, but it did exactly what I expected ... snapped on first contact.  (If you even look at them the wrong way, they break though.)  I really want to be able to cut small holes out of 0.008"-0.02"/0.2-0.5mm aluminum, and didn't think it would be a problem, but I'm not really sure how to proceed now.  I'm assuming that it's just my drill bit, since I have a fairly decent spindle (Wolfgang precision spindle .... I forget the model number).  If someone can recommend a drill bit for cutting 'rectangles' out of this kind of thin metal (ideally that can be purchased online), I'd really appreciate it.

For reference sake, I'm trying to cut solder paste stencils out of sheet metal, and I have aluminum, stainless steel and brass to try, in 0.005"/0.02" (brass), 0.01" (stainless steel), and 0.02" (aluminum).

Kevin.

4
Would you mind letting me know what bit you are using?  I'm just playing with the CNC now and stuck a 0.2mm carbide bit in there, but they are so fragile I'm not sure it will work.  If you have any bit suggestions, I'd definately appreciate it.

How are you converting from Gerber to GCode?  I am just playing with CopperCAM which I use for PCBs, but it seems it can only cut outlines, it doesn't want to cut 'inside' the pads (I'm using the top paste layer).

Thanks for any help.  There isn't a lot on the web (at least that I've found using Google).

Kevin.

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I'm trying to produce solder paste stencils internally to avoid the cost and delays of outsourcing them, and this seems like a natural fit for my CNC mill, but I'm really not sure what kind of aluminum I should be looking for.  I meausred a stencil I have beside me and it is 0.15mm thick, but I'm not sure what type of aluminum it is ... or where in the world I can buy it online.  If anyone has any suggestions on what type of material to use and a potential source, it would be greatly appreciated.

Kevin

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General Mach Discussion / Laser for Cutting PCB Solder Paste Stencil
« on: April 27, 2009, 12:24:45 PM »
I'm interested in converting my CNC Mill to use a laser to cut Solder Paste Stencils for PCBs, but I'm wondering if it's possible to accurately laser cut things down to 8mil?  Can someone suggest (preferrably a reasonably priced) laser that is capable of that kind of resolution, or at least give me an idea of what characteristics I should be looking for?  I'd prefer to cut the stencils in aluminum, but if this isn't possible I could settle for thin plastic transparencies as well.

I've seen some lasers on ebay, but I'm not sure what kind of resolution they offer?

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