Can anyone explain the function of a CMM is to CNC Machining???

[brianklein]

CMM=Coordinate Measuring Machine

What i mean is can a CMM measure the coordinates of an already made object so that someone can reproduce the object through CNC machining center of whatever apparatus is appropiate???

[dpuch]

A CMM has no direct relation to a CNC.

In short, a CMM allows measuring in 3D all at once, at least all the probe tip can access. Depending on the system and software output the measurements in various ways. Simple xy measurements to a single origin, point to point on the part ect. Some can output point clouds for import into 3D software as a surface.

see http://en.wikipedia.org/wiki/Coordin...suring_machine as well.

[brianklein]

If you can get a 3d image from an object using the probe, then you can create a CAD of 3d file of he object on your computer right???

[dpuch]

Yes, but again it depends on the software. That isn't the most common use, but yes. There are of course limitations.

Small variations mean you do not end up with a "clean" solid model. More than 3 points for a flat face means you will have either not a perfectly flat surface, or the points get averaged into a flat face and some minor angle. then for circles, when is it a collection of points and when is it an actual circle.

Think of measuring a cube, but ending up with all the sides 0.01 deg off. A reasonable representation, but not "right" A similar issue is that you end up with a model, but no nominal numbers or tolerance for any features.

Some CMM software (calypso is what I have used) allows making a measurement plan (programming it) by probing the part in the manner you want it to automatically do additional parts. Sounds good, until you consider the above and realize you have to go back and enter in all the correct dimensions and tolerances per print, set features to be parallel or perpendicular ect.

All that said, they are used for exactly that sometimes, and they do deal with these and perhaps more issues somehow.


A more common use (in my opinion) is to verify manufactured parts to a model or the print rather than create a model.

[brianklein]

Do you know of any good places to learn how to use a CMM???

[dpuch]

Originally Posted by brianklein Do you know of any good places to learn how to use a CMM???

It will usually be from a dealer of the CMM you buy, and specific largely for that CMM

[mulciber]

Hello, First post here but I used to run a CMM and still can if I need to. In learning a CMM try a local community college. It may be basic but it can give you a general overview. Learning a CMM is as much software as anything else as well. I learned on though a couple jobs and used Mitutoyo's software(can't remember the name) and most recently PC-DMIS. There is also open DMIS and Tarus, and a host of others... Maybe that helps, I dunno.