William Noble wrote:
today, laser equipment with which I am familiar would have great difficulty
with anything much beyond a basic cylindrical shape - certainly doing Andi
I was thinking the same thing - but overlooked a couple of things the
laser engraving machines makers didn't. The effective depth of focus
on the laser I saw is about 1/8". Beyond that the laser begins to do
what laser folks call "blooming", the beam beginning to spread out,
losing it's effective "crispness". But when the beam is only 0.007"
in diameter, and it blooms 10% - it's still only 0.008" in diameter.
Let me try and put that in perspective.
The finest wood burning tools, the ones with the razor blade thin
tips can, in the hands of someone who knows how to use it, burn
100 lines per inch. I've got a book by a guy named Curtis J. Badger
who is a master bird carver. He uses a pyrography for bird feather
detailing. He does down (sp?) feathers that, from closeup photos,
would require actually touching to realize that they are wood. And
this guy can only do 100 lines per inch with the finest tips he
can find.
So - the surface area on a curved piece you can laser with
adequate crispness IS limited by the laser's effective depth
of focus and a function of the amount of curvature in the
area to be "engraved". I worked out the "effective width"
for 2 to 8" diameter curves and did the illustration near
the bottom of this page (I posted the url earlier and have
since added to it)
http://www.svwoodturners.org/PieceOf...dexingJig.html
So for an 8" diameter sphere, you'd have a circle about 1 7/8"
in diameter to "engrave" in - IF - you set the focus at the
high point. BUT - if you set the focus at the edge of the
the "effective depth of focus" you could double the diameter.
Of course that would mean that the "crispness" at the center
and edges of the "engraving" wouldn't be as crisp as possible,
but it probably wouldn't be noticeable to the naked eye, especially
once you've added color.
Wolfe style motifs would require significant setup and some pretty advanced
math to calculate the inverse projections from the object's surface to the
laser control axis - my recommendation - don't give up your wood burning pen
just yet
Laser engraving wouldn't work with some of her curved bowls
- on the inside. Could work on the OUTSIDE though
But for her shallower ones, and her plates and platters, those
are within the abilities of laser engraver
advanced math and calculations
Actually, the "printer driver" that the laser engraver company
provides
with the laser does a lot of the complex math for you. Computer are
really good at manipulating numbers and digital image files are just
numeric data. So if that "printer driver" tells the laser to not fire
when a pixel is "white", to fire at maximum power when it's "black"
(pierce) and dynamically change the power and frequency of the laser
pulse based on other pixels' "grayness" (carve, with depth defined by
"gray" numeric value), the computer and software tells the laser
what to do and where to do it - and it does it.
The laser's getting instructions on
WHERE to fire (x,y location)
HOW MUCH to use fire (power)
HOW LONG to keep firing at that spot (frequency)
HOW FAST to move to the next firing location
You get to set these "print" parameters, much like
selecting "fast draft", "normal" or "best" with an
inkjet or "laser" printer.
Now the cool thing about using a gray scale image
to act as a plan view contour map for a 3-D shape
is that there's software packages out there already
that let you create virtual 3-D objects fairly
easily - and then convert them into gray scale
"flat" image files. There was such a software
program called Bryce 3-D that was pretty powerful
and fairly easy to use - but - because of the
computational speed of computers at the time
could take hours to render a 3-D object when
you wanted photo realism.
This low relief 3-D "carving" using the laser has
some really interesting possibilities. See the bottom
illustration of a "basket weave" on the url
I gave above.
I've since been playing with gray scale texturing
using PhotoShop and some of the texturing filter
plug ins for it look like they could make the texturing
currently being done with flex shaft and burs and
carving tools all look pretty primitive by comparison.
Imagine doing scales or fur or clusters of tiny convex
hemispheres in areas of a piece.
Right now all the stuff I've done about using the
laser for engraving, carving and piercing are on
our turning club site. I think I'll start doing some
pages on it on my woodworking site. Will post the
url here when I've got something to share.