Best way to measure flatness of an un constrained part

[parrottk]

I need to measure a parts face flatness (amount of warp after heat treat).
the part is 10" OD 9.25" ID .375" Width.
they want it measured in free state no clamps.
Any suggestions?

Thanks

[cmmguy]

uhhhh, a cmm?? what am I missing in your question?

[parrottk]

I guess my question applies more to fixturing.
I am using a Global running pc-dmis 4.1 mr1.
I was thinking of using molding clay to support the part so not to change the shape.

[rangerboat72]

uhhhh, a cmm?? what am I missing in your question?

That's what I was thinking...

[rangerboat72]

I guess my question applies more to fixturing.
I am using a Global running pc-dmis 4.1 mr1.
I was thinking of using molding clay to support the part so not to change the shape.

I use clay all of the time. Works great!

[cmmguy]

Is the part really thin or light that it will move?

If you are worried about the probe deflecting the part then use a angle on your probe like A45Bwhatever to use the side probe deflection instead of the straight down deflection.

[bw_bob]

Try to check the part as unrestrained as possible.

[Peter Warcholyk]

Do not use a straightjacket !!

Check parts in a padded room only !!

Seriously, as mentioned above, molding clay, change probe angles etc.
Is your part very thin and light? I measure relatively flexible parts quite often and have good success using various components from our Rayco fixturing system.

Blessings,
ZydecoPete

[Perry Fisher]

Is the part really thin or light that it will move?

If you are worried about the probe deflecting the part then use a angle on your probe like A45Bwhatever to use the side probe deflection instead of the straight down deflection.

I use clay all of the time. Works great!

Silly putty or poster putty works too.

[parrottk]

Normaly I use Rayco.
Customer says no clamps.
molding clay ok to suport from under side only.
thanks for the help

[cmmguy]

Is the part "magnetable". If so then three point magnet support under the part. Unless it is too flimsey

[#2#]

Is the part "magnetable". If so then three point magnet support under the part. Unless it is too flimsey

Unless you are using the TP20 that doesn't play well with magnets!

[kingsld1]

A CMM is probably not the best choice for measuring flatness. Assuming you do not have a scanning probe, you wil most likely only pick up 70-80% of the total out of flatness due to the limited number of points taken.

DRK

[cmmguy]

A CMM is probably not the best choice for measuring flatness. Assuming you do not have a scanning probe, you wil most likely only pick up 70-80% of the total out of flatness due to the limited number of points taken.

DRK

You are right, a Roundness machine would be better, but then it depends on the tolerance and "flex" of the product. A flat check table would work also. If he had those devices, he may not have asked the question. Just assuming since he asked in a CMM forum, that was all he had at his disposal...

[kingsld1]

I was actually thinking more along the lines of a height gage and indicator on a surface plate.

Mechanically level three points and then sweep the surface. TIR would be the flatness.

CMM's are great tools but they don't do everything well. It's very easy to get caught up in technology when something simple will work better.