Digitizing and working a Cloud of Points

[Fish]

Hi guys,

I talked to Acculux yesterday. They said that their products are designed mainly for human bodies. Hmmm........scan the perfect wife.......now there's a project. Anyway, back to earth. They have never designed, and don't have any inclination to design a system with the accuracies that we are looking for.

As far as the conversion to usable info is concerned, Faro and Romi have software that will convert the points (text I believe) to formats that our CAD/CAM stuff can read. I have heard the same thing about the lack of accuracy before, but apparently, the products are much more accurate now. The proof would be in the demo.

As far as, "What do I use now?" someone asked. I use a Mititoyu CMM. It is about ten or so years old, but it is certified twice a year. It outputs points in text files, which are relatively easy to input into various pieces of software as long as you have taken the data from one relative plain, ie; keep one axis constant. I have never had any real difficulty creating a pretty accurate model from these points. Well, really, the dupicate is a result of all the errors combined, machining conditions included.

The reason we want to change from a standard CMM is that it is too difficult to move some of the parts - they're simply too big and heavy. I have a Renishaw in the machine, which I use to verify measuremnts for the first go 'round of measurements, but not good practice to rely on only one measuring system, I need to have verification of my work. Or rather, my customers need to...

If we can put a man on the moon, than why can't we get a simple....you know what I mean. (Did we reeeaaallllly put a man on the moon?) I smell a conspiracy......

I know I am all over the place here, but, the coffee has run out. As far as needing to know some value before scanning with the laser system is concerned, I think it wouldn't really matter. All the points would be relative to each other. The cloud can be opened in your CAD program, and moved to whatever datum you decide. That's how I do it now. The CMM starts from one spot, but it doesn't matter where that point is. As long as the part is stationary, the points would just be increments from eachother.

Adam

[twombo]

Quote "They said that their products are designed mainly for human bodies. Hmmm"

What a bunch of marroons? They don't seem to be pushing too hard to make a sale!!

They clearly haven't read their own publications very well. The user manual for the RS232 model clearly targets manufacturing processes.

Additionally: They claim a resolution capability of .001" and accuracy of .01% (1 Standard Deviation) at a 500 hz rate. That's pretty good in my book (well within my requirements).

I'll continue my research and share my successes (and failures). Maybe we can get something good going here.

[Fish]

Hey twombo,

You're right, they don't seem too interested in making a sale, or at a new market for their products. The guy that called me just seemed to want to get off the phone as soon as possible. Maybe we could take their idea, and make a real product out of it!!

I don't know if I have this right, but, resolution and accuracy are different beasts. Resolution of 0.001 means that it can recognize features or differences as small as 0.001. But accuracy requires that the system will be able to place the features in relation to eachother, or a datum, within a meaure of accuracy that they are claiming. I look at it this way, I can machine any feature to within a couple of tenths as far as the readout on my machine is concerned, but it my machine accurate enough to claim that it is actually within a couple of tenths?

On that note, the industry has almost gotten to the point where the accuracies requested are barely measurable, let alone repeatable. I have been in shops that claim micron accuracies, but I think they're full of crap. Unless the part is measured on a certified, high quality meausuring instrument, (like a Zeiss CMM), in a temperature controlled atmosphere, the claim is just hot air. I'll get off my soapbox now......

Let me know what else you find, and I'll do the same.

Adam

[HuFlungDung]

Hey Fish, I'll have you know that every part I produce is exactly the size that it is. You cannot even detect a discrepancy between what it is and what it is.

[viperdm100]

Does anyone have any more info on machineing from point cloud data , like how do you get from a .stl format to something I could use like maybe an igs or something.

[Merlin]

Viper,

STL is not really a cloud of points... Sometimes software canconver cloud of point data into a STL. STL can still be worked with if you don't mind working with a larger amount of really small surfaces.

Excalibur will let you import the STL into a CAD model. CAM can then process the data for some operations...most surface type machining.