UV laser for copper, IR laser for circuit board substrate material. Some laser machining 101:
When ablating (not cutting), you need short, high-energy pulses.. not average watts. This means you can do a lot with low "watts" as long as those average watts are concentrated in very short, very high strength pulses. Different lasing approaches can create differently-profiled pulse energy (time vs. energy) with a given average "wattage". I've seen very powerful and fast copper ablation with LED excited UV lasers running less than 5 watts, generating a pulse train above 50 KHz. Similarly, a tea-mode laser pulsing at 500 Hz with a continuous power of 75W very effectively "cuts" fiberglass circuit board substrates. Note that tea-mode lasers typically use a flowing-gas chamber and very high voltage capacitive discharge to cause a laser pulse to form, shaped with a very high peak energy for a very short time. In other words, the pulses "hit very hard". These are usually expensive lasers to buy and operate, but they work quite well. I just wish they could cycle faster. Using an engraving laser can work (maybe), but is sub-optimal. Copper can be used in making mirrors for IR lasers, so you can see why IR lasers don't even touch copper very well. To find the proper laser for a given material, you must look at the light absorption curve vs light wavelength. As mentioned by others, heat dissipation of the material and damage of material by the heat-zone must also be considered when looking at choosing a wavelength and power. You can't always "go faster" by "going more powerful". Lenses and mirrors must be carefully chosen to reduce heat build-up and keep your beam optimal. Pre-lens beam diameter is critical for lasing tiny features (bigger beam entering the lens can allow a smaller final spot size, one of several reasons you will find beam-expanders involved) and lens focal length is important for depth vs focus vs spot size vs optics protection issues. And masking (pre-lens) can help shape and manage beam modes at the expense of final power at the substrate. Hope this was informative, if not actually useful. :-) On Thu, Aug 28, 2014 at 2:33 AM, Mike Payson <[email protected]> wrote: > There is no inherent difference between a laser cutter and a laser > engraver, the main difference is one of setting expectations. If a laser > can engrave a given material, it can generally cut that material also-- > *provided > the piece is thin enough*. Generally with laser cutters that are priced > in the range that hobbyists can afford (even well-funded hobbyists) that > generally means metal is out. I think you can cut very thin (<1mm or so) > stainless on a high-powered (~150W) small CO2, but generally any other > metal can't be done on small machines. > > Copper in particular is hard to laser cut, even on very expensive > machines. It is the worst possible combination for laser cutting: It is > both highly reflective and it dissipates heat very well (aluminum is also > hard to laser cut for the same reasons). Our laser cutter at work can cut > 3/8" stainless steel and plain steel, but it can barely make a mark on > 1/32" copper (I haven't tried anything thinner than that yet). > > > On Thu, Aug 28, 2014 at 3:36 AM, Kenny <[email protected]> wrote: > >> My understanding is that an engraver is like a cutter with less output >> power. Enough power to leave a mark, but not much more. The level of >> precision probably isn't implied in either case. >> >> If you are looking at engravers on Ebay, they are probably low power CO2 >> which can't engrave copper. There are IR and UV lasers designed for >> prototyping PCBs, but they cost somewhere in the $60k range to get >> started. >> >> There are other options for using a CO2 engraver, I suppose. Like >> painting on a chemical resist layer that can be engraved off, leaving >> exposed copper to be consumed by your favorite acid. >> >> http://www.instructables.com/id/Double-sided-PCBs-with-a-laser-cutter/ >> >> >> -- >> Kenny >> >> -+---+++-++-++++--+------+-+-++--++--+-+-++--+++-++----+-++-+++---+----+--+----+ >> >> >> >> On Wed, 2014-08-27 at 22:15 -0700, benjamin barber wrote: >> > Question: is a laser engraver a smaller and more precise version of a >> > laser cutter? >> > >> > Question: can a laser engraver be used to manufacture PCBs? >> >> _______________________________________________ >> dorkbotpdx-blabber mailing list >> [email protected] >> http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >> > > > > -- > www.MakersToolWorks.com - Tools for Makers > > _______________________________________________ > dorkbotpdx-blabber mailing list > [email protected] > http://music.columbia.edu/mailman/listinfo/dorkbotpdx-blabber >
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