Karl Townsend wrote:
Your laser digitizer sounds interesting. Please tell me more about it. I
do a lot of designs for my CNC plasma table by taking a photo of the part
and turning it into a .dxf file but accuracy suffers a little in the
process and I end up checking all the measurements if it is a critical
part. Artwork isn't too fussy but some of the machine and equipment parts
I do need to be right on.
Steve


I bought an Omron laser displacement sensor off eBay. It puts out 4 - 20
milliamps over distance of 1.1 to 2.0" away. I mounted it in a taper 40
holder. I then go back and forth over the part in my CNC mill and record
distances plus X,Y,Z dimensions off the control. You end up with a ton o'
points. Then the hard part, make it into something usable. So far, I'm
learning Rhino. I'm not too good at this step.

If you got time, there's also a point probe that you can build or buy. With
that you move the mill to an X,Y location and then move Z till the probe
touches; record point;repeat. Much slower and slightly less accurate. But
still way more than you'd need for a plasma cutter.

I did the photo to .dxf thing with my business sign. Next time you drive by,
look at the new signs. Took more time than if i had just started over from
scratch.


Karl





I've taken "lines" off of boat hulls using a few cheap laser leveling
devices. Anything that will draw a bright thin line on the hull.

One set going "up" the hull and one set running lengthwise.

Then I level up in front of the hull on the load waterline and snap
a digital picture. (Same for the aft part).

I play with the lazer photos a bit first. Kinda Pre-procesing.
The idea is to get the line as thin as possible. Those lines
show up brighter in the photos than they do in real life.
I do this by playing with the brightness and gamma settings.

The thinner the lines are the more accurate the trace.
These pics are then imported into my CAD software (no it ain't Rhino!)
and traced.

While there may be some absolute accuracy lost in the tracing process,
I can usually make it back up in the fairing process.

I'd suspect that proper fairing will help with even small parts.
As long as you can get a good sied photo anyway.

http://www.home.earthlink.net/~cavelamb/draft.htm