CMM Info

[georgebarr]

Does anyone know of a discussion board to find information on how to build your own CMM (coordinate measuring machine). This allows one to do rapid prototyping by getting a parts dimensions and inputting it into a CAD. Since commercial ones cost more than $4,000+ it would be better if I build one myself. Any web sites on how to build one or discussion groups is appreciated

Thanks,

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[cncadmin]

Right here

[Max]

Something like this?
http://skalarcnc.netfirms.com

The guy who owns this company, Dennis Sullivan posts at ShopBots forum and seems to be very helpful.
You might be able to contact him to see if there is a forum specific to that.

Also, the ShopBot has a probe that inputs coodinates into the computer.

[Wjman]

Try http://www.cmmtalk.com, you might be able to get some info.
Mark...

[HomeCNC]

How about the ability to add a probe to your existing CNC router and turn it into a CMM? This would be handy and I would love to do it with my CNC router.

Some how you would need to feed back the signal from the probe to the P.C. Has anyone here ever seen this done? What software was used? What probe? How was it connected to the P.C?

[kdoney]

I did it on my sherline mill and my router. I used a maxnc touch probe, later I used a simple proximity switch (about 1/10 the cost). These where hooked up to a pin on the parallel port on the controlling machine running TurboCNC. Two special g codes where used on turbocnc for movement, one moves until the touch strikes the workpiece and the other probes a two dimensional area backing off after a contact. All points are recorded automatically and the precision is the same as your stepper control. This may be good or bad. You can get Turbocnc for free to try it and almost any sensitive switch can be used to test the system. I suggest you use the smallest machine available to do the readings as the scale of error is important. On the sherline with the proximity switch I get repeatability of ~.001.

[georgebarr]

MaxNC.com has a cheap 3D digitizer. My question is does it measure just the vertical height only or can it measure or sense all three axis (x, y, z)? Also, how accurate can it measure (how many millimeters is the smallest it can measure). I would email maxnc.com but they don't seem to have an email address.

Thanks,

[cnczane]

kdoney,

I'm interested in your simple proximity switch solution if you're inclined to post a picture or a description. Thanks.

[georgebarr]

How does a touch probe compare with a laser type probe? I am assuming the laser type has a faster scanning capability and is able to scan soft things likes plants/flowers used to machine wooden decorated things.

Does the proximity switch (very inexpensive) probe really work? I am thinking about using a piece of rod with an inexpensive proximity switch attached to the end and a wire from the switch to the parallel port. Is this all that is required to get it to work? What kind of proximity switches? Any www sites of example switches? How about a momentary switch from radio shack?