On Tue, Mar 13, 2012 at 10:42 AM, Gene Buckle <geneb at deltasoft.com> wrote:
On Tue, 13 Mar 2012, Ethan Dicks wrote:
I thought of that, but I also figured that the
conical nature of the
hole left behind from a bit would catch the light better than a
roughened surface etched by a laser....
I had one project recently where the cut time was 3 minutes, but the
text on the item took 7 additional minutes.
Ye gods man, how much are they charging you to use the laser?
We pay $35/hr station-time which includes the entire time we are
setting up materials, adjusting settings, and laser-on time. The
other billing model I know of is laser on-time. NYC Resistor (the
hackerspace in Brooklyn that spawned MakerBot Industries) charges $2
per minute of laser on-time, for comparison.
One raster-only job I did was etching aluminum tags. 12 tags took 15
minutes of laser-on-time to scribble text on. Mixed projects (like
enclosures for Adafruit clocks) take 15 minutes of laser time to cut
out the parts and another 15-20 minutes to raster the text. Add
another 15 minutes to set up the machine, position and remove the
materials and we're at 30 minutes for simple jobs.
If I wanted to make some replica KMG display digits that are 1"x2",
one set of 10 is approx 20 sq in of rastering and somewhere around 48"
of cuts. For 3mm acrylic, the etching will take at least 10 min and
the cuts under 5 minutes. That puts the production cost of the
acrylic portion of each digit over $1 to which is added the enclosure
and a PCB and probably 20 SMT LEDs. Rough guess is $25 in tools and
materials to make one 0-9 digit display.
The CNC rents for less and could more quickly make line of 1/2-depth
holes than a laser rastering over the entire face of the digits doing
multiple passes to etch to depth (the laser would be faster on a
single pass, probably, but I don't think it would produce good results
in one pass - you can only etch so much at once).
One does not have to rent much time before an inexpensive Chinese-made
laser cutter starts to become economical for hobby work. Cost of
entry is around $1000 and there's more fiddling than with a $10K
Epilog, but if it's not about minimizing minutes to be profitable, and
the tasks at hand fit the lower power and smaller bed of a cheap
cutter, for 30 hours of station time or 8 hours of laser-on time, one
can rent a good machine or buy a cheap machine outright. I know this
opens up the perpetual can-of-worms about good tools vs cheap tools,
but a good tool in this case costs 10X what a cheap tool does. It
might or might not deliver 10X the reward. It certainly isn't 10X
faster if time is a factor.
-ethan