Opinions/Advice on CMM purchase

[dgeesaman]

Hello all,

We're looking at purchasing a bridge-type CMM to replace an old B&S Validator. We're looking at bridges with a working volume of about 60x50x120" and .0002-.0003" accuracy. We measure machined housings with flat faces and cylindrical bores, inspecting for feature position and form.

If you can offer your opinions on these questions, it will help me immensely to learn from a source that doesn't also have something for sale.

1) What are the pros/cons of the major CMM brands? Which ones are known for having better intrinsic accuracy?

2) Knowing what you know now about your CMM, what would you have done differently if you were to purchase your equipment again?

3) Refurbished vs. new? We're leaning toward refurbished.

4) Some CMMS have add-ons to allow checking of gears on a traditional CMM. We use a lot of AGMA 10 quality helical gearing and would like to do some basic checks. If you're doing this I'd love to hear how it works for you.

5) We have some "tall" housings that will be measured horizontally on the table and require 8-12" of horizontal reach. I know this causes a loss of accuracy, but it will be an important capability for us. I'd appreciate any suggestions about fulfilling this requirement.

Thanks in advance.

[PixMan]

The only ones I've used are an old manually-operated Mitutoyo, and a fairly new Carl Zeiss programmable "Contura". All I can say is WOW, that Contura with Calyso software and articulating Renishaw probes was simply the nicest, most precise and easy-to-use CMM I've ever had the opportunity to play with.

I had to qualify a 4.5" long diesel engine fuel metering needle that had 104 features, including runouts, roundness, and profiles. Holding the part in a small magnetic V-block, the inspection was done in less than a minute per piece. The part was very thin, and easily deflected by probe pressure, but the Zeiss/Renishaw had such low force that was no problem.

The newest stuff out there is even better. There's some pre-owned systems they have on their website, look under "Products" then "Pre-owned".

http://www.zeiss.com/IMT

[specfab]

My direct experience with CMMs is limited, but I also liked the Zeiss line. We had an Eclipse DCC unit with USOFT(?), as I recall. This was a 1996 machine bought new, and outfitted with the standard Zeiss ST probe head. The reason we chose it was based on the spec accuracy of the machine: volumetric accuracy at 2 microns over the envelope, about 18 x 20 x 18. It worked well, and I found it easy to use, even as a novice. Later experience with a mid-90's B&S MicroVal Pfx and PCDMIS was much less satisfying, but I didn't ever have enough time at it to get any proficiency.

[dgeesaman]

Thanks.

I've never heard a bad thing about a Zeiss product but their preowned line is not as large of a volume as we're looking for.

I did find this picture of a CMM just like the one we're replacing: http://www.time-compression.com/x/gu...name=&id=10989