Re: "New kid on the block"

The simpler 3D laser scanners I have used are nothing more than laser range
finders. They have a laser and a camera(one piece unit), the laser shoots
directly down on the z-axis reflecting back to the camera at about
20degrees. The laser is mounted to the machine head and software
simultaneously tracks the x and y axes and calculates the z depth. This is
more time consuming than the more advanced 3D scanners, but it does the
trick. An important part of this system however, is the need to reduce the
data you don't need while maintaining the data that is vital to the form.
For example, a large flat area can be scanned at a very low resolution,
whereas an edge or pocket would require a much higher resolution to be
reproduced accurately. Since you would generally scan at one resolution, you
need software to reduce the data where you can. For those scanning with the
intention of using CNC to reproduce the piece, this method is IMHO the most
economical, because you can use your machine to control the laser movements.
One drawback is the "shadow" produced by the 20 degree reflection angle.
There are far more sophisticated systems that use moving lasers and camera
tracking, that are able to scan very rapidly, and depending on the software
can output anything from pointclouds to NURBS curves or NURBS surfaces.
These devices are much less expensive than they were even a year ago, but
require powerful computers to process the enormous amount of data generated.
Between the scanner and the computers, your looking at a hefty investment
for this type of setup.

Patrick Huss



-----Original Message-----
From: Arne Chr. Jorgensen <instel@...>
To: CAD_CAM_EDM_DRO@onelist.com <CAD_CAM_EDM_DRO@onelist.com>
Date: Thursday, July 15, 1999 4:32 AM
Subject: [CAD_CAM_EDM_DRO] "New kid on the block"

>From: "Arne Chr. Jorgensen" <instel@...>
>
>Hi there !
>
>I have been listening in for some time now, - and I have some
>questions.
>
>1.
>
>I used Autocad under dos, and I now have two tablets:
>
> - CALCOMP 2200
> - GRAPTECH Digitizer KD4300
> How do I hook up these ? Does anyone have manuals for these ? Do
>you need any special drivers to run them ?
>
>2.
>
>I am using Linux, - and I just hate the "microsoft-box" ! I am just
>sorry I didn't switched to unix or linux - years ago. But I admit,
>- it can be difficult sometime. I have used 6 months to get the EMC
>working ! I used a 486, and I recall that someone said they wanted
>to set up a 486 in their workshop. There is some files that needs
>to be modified to get it working with the RT kernel, because it uses
>shared memory a little differently:
>- in lilo.conf : append="mem=xxx" - set aside less than 1M
>- in /usr/src/linux/include/asm-i386/param.h - change #define
>EXEC_PAGESIZE 4096 to
>
>#define EXEC_PAGESIZE 1024
>- then the good guys at NIST has done corrections in the
>emc-06-Jul-1999.tgz
>
>I just wanted to pass this along.
>
>3.
>
>Does anyone know where to change the xemc, so that it opens in a
>window that is not larger than my screen ? ( I can't use a higher
>resolution - I need to change the window size )
>
>4.
>
>Does anyone have a script that strips off all the quotes from the
>digests I receive. I use a lot of paper to print out the same info
>again and again.
>
>5.
>
>I want to use the EMC software to run servo motors, not steppers.
>Is there anyone who has some schematics on servo amps ? I would
>like to make my own.
>There is also some problems, because my motors don't have any tacho
>generators. To get tighter servo loop, you need that. Does anyone
>have an idea how to make a tacho signal from the encoders ?
>I know about a chip that does this, but it will only work for sinus
>shaped encoder signals
>( SGS L291) - any ideas ?
>
>6.
>
>What is a DRO ? - I guess it is a Digital Read Out device, - but
>what is EDM ?
>
>7.
>
>Someplace I read that some wanted to divide this list. Not everyone
>is interested in ball screws etc., I understand that. But what if
>there were a DIGEST made over people that uses this location, with
>information about what and how many uses Linux, EMC, skills,
>interests, etc. Then you could post a question to those who most
>likely would know what you would like to know, instead of having
>everybody answer the same question. Sure all comments would be ok,
>but I guess there is someone that seldom speaks up, - and they may
>have some very interesting projects going on, - something others
>would like to join in on. Just a thought.
>
>8.
>
>Someone mentioned a laser scanner for 3d. Does anyone know what
>kind of principle they use to do this ? ( I know of several
>possible solutions - but would like to get some info on how they do
>it )
>
>
>
>Best regards
>
>//ARNE
>
>
>
>
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>
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