Complying with Ford customer requirement 4.35 Variable Gage Studies

[kat.k.]

Hello!

The Ford customer requirement 4.35, page 19 says - Variable gage studies should utilize 10 parts, 3 operators and 3 trials.

Our procedure says to use a 10 piece R&R study on new gages. From there on out it is a 5 piece (Range Method) study.

Standard gages such as calipers and micrometers, is only when new and if repaired, then they get a 5 piece study. There is a electronic 10 piece study stored in our gage system.

Our gages that check a specific feature on a part such as R/O gages and timing fixtures require a gage R&R study every year. These also have a 10 piece study when new and stored electronically then from there on out they have a 5 piece Range Method study.

I'm not quite sure we are meeting this requirement. It seems like we should be doing a 10 part, 3 operator and 3 trail study each time on Ford parts.

But, before I make things harder than they really are and create more work for the gage technicians, I would like to get input from others like yourselves.

Also trying to keep the standard gages used for other customers separated from Ford parts will not be easy. Do any of you have solutions or suggestions?

Thank you
Kat.k.

 

[bobdoering]

Re: TS 16949/Complying to customer requirement

If you do the PPAP MSA following the Ford requirement, and it meets it, then you should have satisfied the requirement.

There is nothing in that section that requires annual gage R&R, so all of the annual gage R&R's are for your academic pleasure, beyond the Ford requirement. There should not be a need for annual studies, as there is no time function to gage R&R, unless it was not performed correctly to begin with. All gage r&r is used to determine is if the gage is the correct gage for the job. Calibration is the time function of a gage - linearity, stability, etc. It answers the question is the gage still measuring correctly.

 

[kat.k.]

Great! Then I should be good on this and it makes sense too.

Your answer to this question brings up more for me to ask...

1. Your response - all gage R&R is to determine if the gage is still correct for the job.
Calipers are standard gages with three mechnisms, IS/OS jaws as well as depth rods and can be used for many features. They may be O.K. for checking a ID chamfer with .030 tolerances but it isn't for checking a chamfer ID with only .010 tolerances. Do you have any suggestions on how to control calipers on jobs for what they are used for?
And what to do we do when just one of the mechnisms doesn't pass calibration??

2. Your response - calibration is the time function of a gage - linearity and stability.
We are not doing any of these studies, only calibration and R&R. Is this something we should implement?

Thanks
Kat.k.

 

[bobdoering]

1. Your response - all gage R&R is to determine if the gage is still correct for the job.
Calipers are standard gages with three mechnisms, IS/OS jaws as well as depth rods and can be used for many features. They may be O.K. for checking a ID chamfer with .030 tolerances but it isn't for checking a chamfer ID with only .010 tolerances. Do you have any suggestions on how to control calipers on jobs for what they are used for?
And what to do we do when just one of the mechnisms doesn't pass calibration??

2. Your response - calibration is the time function of a gage - linearity and stability. We are not doing any of these studies, only calibration and R&R. Is this something we should implement?

1. Well, honestly, that is tough. Calipers are great general tools, but as we know - and the horror stories have been told - they have some limitiations. They do not have carbide surfaces - so they can wear. Fast, in some environments. If your system assigns calipers to a job, and your work instructions tell the operators which dimensions to use the calipers on (a la control plan), then the missing link (if there is one) is responsible supervisors that ensure these requirements are met.

As far as what to do if one of the mechanisms does not work? Well, you could assign it to a job that does not use that mechanism. Some have mentioned they have removed the mechanism (dangerous - how do you know you didn't ruin the good parts with heat distrotion from grinding, etc.?) Best bet, be prepared to replace worn out gages. If it gets too expensive, then it is nature's way of saying you need a different gage (and you will afford it because either it will last longer, or it will have replaceable parts - like an indicator.)

By the way you missed the 'step' measurement function of a caliper!

2. Your calibration should cover linearity - checking 4 or more locations on the gage against a standard. You might not be as sophisticated as to draw a line through the data to see if there is a linearity issue, but it is very basic linearity. As far as stability, it is good to do, but really important for gages that wear over time with little notice (like air gages) or electronic gages with drift.