Digitizing and working a Cloud of Points

[Merlin]

MPE asked a question about how to process a Cload of Points from a Digitizer...

This is a very interesting and difficult subject because what you are really talking about is reverse engineering something that is already made. This is common in the racing industry where engine heads and ports are hand ground to make the first port and then folks want to duplicate the other heads to make them all the same.

Its real important that you full understand the actual process and the limitations to the process of digitizing.

[MPE racing]

One of the universities here has a laser type scanner. It is a hand held scanner that uses "GPS" style technology to know where the scanner is positioned. The only problem is it can't scan metal and it can't scan internal. However, I'll take a plug of the port using a pliable silicone(probably from a dental suuply store), and then scan this to obtain the port.
I'll look for the link to their site

[MPE racing]

http://www.cpai.uq.edu.au/scanning/

Have a look through this

Greig

[Fish]

Now this is an area that I'm reeeeaaaaalllllyyy interested in! I just started doing work for a Pro-Modified Dragster team here in Vancouver Canada. The budget is substantial enough to allow me to get what I need to accomplish our goals.....finally. Anyway, I am looking at a Faro or Romi arm, and accompanying software package to convert the points. I have downloaded an eval copy of Rhino, but I haven't had enough time to learn it yet, though I'm told it's pretty easy as far as solid modelling programs go. I'll keep you posted if your interested.

What kind of racing are you guys involved in? Anyone up for the "One Lap of America"?.

Adam

[Merlin]

Fish,

Excalibur has users in all facets of racing...NASCAR, BIKES, JET SKIS, SNOWMOBILES and I'm sure many others I am not aware of.

The key is to get good data...The Faro and Romi arms are not really a good choice since they both use a mechnical probe with a ball tip. This means you are not really getting the point of the surface you are touching but rather the center of the ball on the probe tip.

The better systems will use a laser or optical system that actually returns data points on the surface of the object being scanned.

Not that you can use the mechnical methods, its just they are more difficult and take much more time.

[MPE racing]

Fish. MPE stands for Motorcycle Performance Engineering. We make components for drag racing really.
The FFR team of Al Miles and Jerry Gordon just won the Canadian(CMDRA) Pro-Drag championship running one of our dataloggers actually.
The datalogger box is a billet aluminium item made using Excalibur.
go to

http://www.stripbike.com/ubb/Forum9/HTML/000610.html

to have a look.
Greig

[twombo]

Here is a device that maybe the breakthrough in laser metrology many of us are looking for:

http://www.aculux.com

Total cost in RS 232 configuration is about $1200. Given, most manufacturers are charging $10000 to include a laser metrology capability, this a real bargain. I am not complaining about their prices... they have to recoup their investment somehow. I just can't afford the price of admission and, fortunately, advances in technology and subsequent reductionsis prices is always on our side.

Check out the downloadable PDF manual for the OEM version. Some basic code and operating data is included in the manual. Any DOS gurus out there willing to develop code to interface this puppie?

I have presented my concept to a luthier friend of mine who has extensive software engineering experience with x86 and pentium class microprocessors who has similar CNC ambitions and he is going to put some time into developing an application for scanning and creating a cloud of points.

Additionally, a web acquaintance of mine tells me he is scanning ing DOS mode at pretty fast rates already in DOS Mode.
I have asked to share his code and will pass along what I can.

Art Fenerty of Mach 1/2 fame is working up support for the serial port in Mach 2 for release in the future. My guess is that if he gets enough interest from the user base he may be inclined to up the priority of development.

[Fish]

I just looked at the Aculux laser site. It is a good idea, but the accuracy is only 0.003". I know the touch probe system is time consuming and a bit of a pain since what you actually get is an offset of the surface, but the accuracy is down to 0.0002" (at least that's what they advertise). I have worked with other conventional CMM's, an this was standard practise. The trick was to have software capable of generating the true offset surface without taking two days to process.

Hey Greig, do you guys have a website?

Adam

[twombo]

Fish....Tell me more. I can live with .003" but I currently have nothing at all in terms of proven technology and will be happy to chuck the model in the machine and let it measure until it's done.

What do you use??

Laser is great for the future. But....a model in the end is just a model.

[Merlin]

Fish,

I know the systems say they have 0.0002" tolerance but that is in a perfect world. For the type of work you are doing, I have never seen a Faro do better than 0.005"...especially when you have to then offset the surface which compounds the error.

Perhaps you could get a more accurate version of the Aculux by calling and talking to them. It is always better to work from the original surface data if possible!

[twombo]

All my wooden parts finish with scapers anyway. The last few fractions of a mm are by hand. I just want to be able to prototype in a timely manner and test finished item tolerances.

Guess I need to talk to Aculux.

The Faro and Miniscribes are really too pricey and slow for my taste anyway.

Imagine trying to scan a big "ole" string bass.

[MPE racing]

Fish we're at www.mperacingonline.com

I'm just curious how you would interface this into a pc to obtain your cloud of points.
Maybe I'm thinking too simplistic here, but here's what I'm thinking:
You would attach it to the spindle in the machine. Run the machine in a series of lines across the job to scan the whole item.
You would need to know the X,Y,and Z value for each scanned point.
So you would to dprint to the PC the x and y location of each movement, and them also somehow obtain the Z value from the laser into the same line of code.
Possibly there is a way to connect the laser in some form af analog or digital form that the controller can use to convert the input into a number and set a parameter with that value so when you do the Dprint, it comes out in the same line of code.

Am I thinking along the right lines here or did I just confuse myself

Greig