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repeatabilty and measurement

#17546

repeatabilty and measurement for quality | 10 September, 2001

Hi guys HELP!!!!!!!!!!

I have been tasked with working out a chart to show calibration acCuracy and that my machines are in control I say to myself I know they are cause I have no misplacement of fine pitch but this is not good enough for my collegues

I am presently measuring placement accuracy with glass parts and plate.

BUT HOW DO I AQUATE THIS INTO A GRAPH EASILY TO SHOW THE QUALITY DUDES THAT MY MACHINES ARE OK

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Michael Parker

#17548

repeatabilty and measurement for quality | 10 September, 2001

Are you doing actual measurements of the dummy parts placements? or are you just doing a visual go/no go check?

If doing actual measurements, be sure to use mil inch units of measure rather than mm. Mil will give you more accurate readings. mm forces some round off that cannot be resolved within its numbering system.

Be sure to use a 20X or greater magnification when inspecting and doing a measurement. I have used the CyberOptics LSM @ 100x with good success when no other means were available. Don't rely on calipers as I've seen some engineers using.

You need to start with the machines placement accuracy spec. from the supplier. They will advertise an accuracy of +/- 5 mil.s or something to that effect.

Next, you need to characterize each machine and finds it's offset bias. It will always place a component slightly off target, a combination of +/- X and +/- Y. Determine the repeatability of bias over a large square area. It may place well when close to x=0 and y=0, but degrades when x=12 inches, y=12 inches, etc.

Using a spreadsheet (Excel or other), record daily measures of hitting the target (or how much off) when x=0 and y=0, and when x=12 inches, y=12 inches, etc.

Display the daily measures on a scatter plot graph, using the spec limits of +/- 5 mils. as upper and lower limits. Be sure your daily measures fit between the limits or initiate a recalibration.

This is just my opinion, but as a long time "quality dude", I would be satisfied with results displayed in a manner I've described above.

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#17551

repeatabilty and measurement for quality | 11 September, 2001

The fine "quality folk" that are laying this reasonable requirement, but are unreasonable in their attitude and approach. They should be sitting down with you and explaining: * Why the requirement is reasonable and necessary. * What are the acceptable alternatives. * How to go about fulfilling the requirment. * Who is providing the resouces and assets. * Etc

It just chaps my fine little blank when these fine little quality nazis come around: * Flippantly issuing their fine edicts. * Providing no fine help or resources to the up-standing but sorely over-worked up-holder of truth, justice, and the American way in production. * Wandering back to their cramped little warren to play solitare.

Tell them to go pound salt, until they figure-out how to help you get the job done.

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Michael Parker

#17554

repeatabilty and measurement for quality | 11 September, 2001

....and now you have the YIN and Yang of it. Of course, Dave's perspective is just as valid as mine.

By the way, I prefer Hearts over Solitaire!

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#17555

repeatabilty and measurement for quality | 11 September, 2001

Hi guys

Thanks again for the help you have been a great help to me.

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#17556

repeatabilty and measurement for quality | 11 September, 2001

Is that why they call me a "ying-yang"?

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