Re: Laser Engraving - valueable information

Jim, you have just shared a wealth of information, which no amount of
money could buy. Thank you very much for taking the time to put your
experiences in writing. This information is very valueable.

Whelen

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Jymmm <jymmm@y...> wrote:
>
> Hi Whelen,
>
> Last year I was looking to purchase a laser engraver.
> Here is what I learned, take it for what it's worth.
>
> Of the three big boys (Epilog, Universal, GPC) they use sealed
(gas) CO2
> laser tubes. Sealed CO2 tubes have a shelflife of about 3 to 4
years, even if
> in use or still in the box. After that, their power output decreases
> (basically).
>
> Most of the mfg's can recharge and replace the mirrors in the tubes.
>
> The older type of CO2 laser tubes are flowing (as opposed to
sealed), where
> you have the welding supply mix you up a special receipe of gases
and you
> just refill the tank when it gets low.
>
> CO2 lasers can NOT mark/etch/cut metals. The wavelength is wrong.
> You'll need a YaG laser for true metal work.
>
> The metal marking stuff is just like pottery glaze.
> You brush it on the metal, the laser "cures" it, and you wash away
the rest
> with water. It does not mark the metal in any way.
>
> Now, if you have anodized metal, a CO2 laser can "bleach" the
anodize itself
> (usually comes out a off cream color). It doesn't matter what color
the
> original anodize is (red, blue, gold, etc) the bleaching will
always be the
> same off cream color.
>
> You can even bleach the color out of denim to produce patterns in
fabric.
> (I was told this process of bleaching fabric it patented, so...)
>
>
> All of the laser use flying optics (moving mirrors to position the
beam).
> The laser *MUST* be focused to the top surface of the material
before each
> run. If not you will get a gooey blob (in the cast of plastic), so
altering
> the Z height itn't going to do it.
>
> A 35 Watt CO2 laser can cut 0.25" thick wood. But if the wood is
dense it
> might be better to make two passes instead of one big one to get a
nicer
> finish. I took a scrap piece of teak wood and had they cut it for
me. Not a
> pretty sight on such a low power laser. Too slow feed and low
powered cause
> the sap to melt/burn and char the edges.
>
> The power levels (like depth) is controlled by pulsing the laser
(plus
> something else I can't recall at the moment).
>
> They all use HPGL (plotter) and not G-Code for controlling
movement/power.
>
> Also most all of them are installed like a printer and most
everyone in the
> engraving industry uses Corel Draw.
>
> I started to ask around about used lasers and found someone that
engraves urn
> boxes (beautiful work) professionally. He was selling a 75 Watt C02
laser
> engraver because it was too low power to engrave on the surface of
softwood
> 0.125" thick in a reasonable amount of time.
>
> I hope I didn't ramble too much and the information was helpful.
>
> Jim...

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