Simple assembly service - How could we do process study? Attribute data

[zh_maggie]

Hi, as a service company providing simple assembly service, how could we do process study, we are even waived initial process study during PPAP, because it's attribute data.
How can we comply with 8.2.3.1?
Thank you very much!

[bpritts]

Hi!

You can consider p charts, c charts or u charts. These are attribute based, one tracks defect incidents, the other defects per unit (think of # of components missing, or # of dents/dings/scratches.) There will be details in any general
SPC reference book - e.g. Acheson & Duncan or Grant.

One challenge is that you need a lot of data to show statistically meaningful
capability. In automotive our customers will accept a variable data study
with as few as 20 - 30 points, while attribute studies must have thousands
of points.

Do these based on "first time" capability, that is, before any re-work or
repair. That will help you get a good read on actual performance.

Regards,

Brad Pritts