Best Fit Alignment - Bolt Circe

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Tking
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Best Fit Alignment - Bolt Circe

Post by Tking » Tue Mar 15, 2016 9:11 am

We constantly have bolt circle type gages to layout and certify. The attached image is one example.

To lock rotation, it seems we can get the "best fit" or best layout using CMM Mangers "best fit alignment."

There really is no -C- datum, but you need to somehow clock the part to establish if the features are properly spaced about the bolt circle.

The issue I have is; you have to type the nominals in to perform the alignment. Once you type them in and run the alignment, all of the nominals change.

*** Not all of the gages use GD&T. Some are simply coordinate dimensions and tolerances. ***
Sometimes we layout the actual bolt circles on the parts and not the gages themselves when we have re-work projects. (I don't believe the GD&T bolt circle function will be the fix I need.)

A) Is there a way to lock the nominals for each feature so they do not need entered again?

B) Is there a better way to align and measure these gages using a different set of CMM Manager tools?

Thank you for the help!
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medupriest
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Re: Best Fit Alignment - Bolt Circe

Post by medupriest » Tue Mar 15, 2016 11:57 am

Hello,

I am not really sure why the nominal values need to be re-entered on your side. I just tested this on my end and the nominals do stick. What version are you running?

For the print you attached, best fit alignment is likely not the best way to go as the alignment will undo your previous alignment structure to your datums. I think you would be best suited on that part to clock to a hole at one of the four quadrants or construct a line between two of the holes at opposing quadrants and align to that. I would then report the composite position of the entire pattern and set the datum features to -A- and -B-. When you report the composite position in this manner, the rotation should be unlocked to allow for a best fit only in rotation.

Alternatively, you can extract the raw data from all of the circles and do a Cloud-to-CAD comparison, but naturally, this will not give you the positional call-out information.

Tking
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Re: Best Fit Alignment - Bolt Circe

Post by Tking » Tue Mar 15, 2016 2:49 pm

Thanks for the reply, medupriest!

I'm running V3.5 and the nominal values in the feature box always adjust. It seems to set the actual values to the best fit and adjusts the nominal values to some calculation from original and deviation values. Anyway...

The gage checks location and fit/function of a bolt circle to the center bore. The location of the composite picks up some bonus tolerance based on the size of the bore. (MMC)

I shall try composite position the next time I lay one of these out.

The problem with clocking to 1 or 2 holes in the quadrants is you set the entire gage to those positions an call them perfect. The may in fact be off a bit or even out of spec. One hole throws the entire gage out. It's not a very efficient way to find what's really in and what's really out. You might skew the alignment by manually rotating the alignment by say .01 degrees or less and the entire thing comes in. I'm trying to take the guess work out and speed up the process.

Thanks for the help!

rhcedar73
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Re: Best Fit Alignment - Bolt Circe

Post by rhcedar73 » Thu Apr 07, 2016 5:46 pm

If I am understanding you right, I think the 12.7 dimension on top is the key. If a line is constructed from the top hole to Datum A and used for the clocking, then the 12.7 would tell you how far your clocking is off.

I have had to do this with a lot of parts I check. If it is off, I can use the data I get to help the machinist make an adjustment. Works pretty good.

If I am off base, then please just ignore me.


rhcedar
QA Assurance Tech
Arc Engineered Products
rhcedar
QA Assurance Tech
ARC Engineered Products

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