Flatness gaging method

[rinkman11]

Because the rollers that we manufacture are up to 15" in Dia. and 230 inches in length, a stationary gage was to much expense for this company. A portable apparatus(hat if you will)which is 12" long with 45 degree angles was created to be placed on top of the roll with an indicator placed centrally.The indicator has a ground flat on it. This unit is then pushed across the roll at a distance of 24" with software hooked up to the indicator measuring the variation in 24 " Some say this measurement is flatness others say it is profile. I say it is not an accurate way to check anything.

What do you think?

 

[Belanger]

Having trouble visualizing this, but I am leaning toward profile. There isn't really anything "flat" about rollers.

John-Paul Belanger
Certified Sr. GD&T Professional
Geometric Learning Systems

 

[powerhound]

I agree with JP. In order to check flatness, the thing being checked must be flat. If I am visualizing your set-up correctly, you are really checking straightness...sort of, but not exactly.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II

 

[axym]

I'm having a bit of trouble visualizing this as well. Assuming that the "top" of the roller is on the cylindrical surface, it sounds like the "hat" apparatus checks surface line straightness per unit length.

Evan Janeshewski

Axymetrix Quality Engineering Inc.

http://www.axymetrix.ca

 

[pmarc]

Some say this measurement is flatness others say it is profile. I say it is not an accurate way to check anything. What do you think?

And what you and others would like to check?
I believe there was an idea behind this setup.

 

[MintJulep]

I'm picturing a long V block with an indicator at the apex of the V.

Is that right?

That would measure some combination of geometry between the points of contact of the two sides of the V and the indicator.

Since you have no way of knowing if the indication is because of something directly at the indicator location, or due to the V contact patch not being "perfect" you really have no idea what you are measuring.

 

[rinkman11]

The hat (which is what it is called ) is actually a big 12" V block made out of micarta that rides on the same 12" diameter of the tube that readings from an electronic indicator are taken. The thought in the making of this was that the 12" V block is contacting the diameter enough where it would not influence readings. I believe it works to a degree but how can this be accurate when your taking readings from the same surface your V block is riding on?

 

[MintJulep]

contacting the diameter enough

How much is enough?

Let's for a second pretend that the V block is "perfect".

V block __________________
Cylinder /\___/\___ __
^^^^\/

Is that "enough"?

 

[powerhound]

...and you're still not checking flatness.

Powerhound, GDTP T-0419
Engineering Technician
Inventor 2010
Mastercam X5
Smartcam 11.1
SSG, U.S. Army
Taji, Iraq OIF II