Detection rank for sampling vs 100% inspection & 15x vs 400x magnification

[mlshim88]

Hi,

Appreciated if anyone could advise the following situation :

1. Case 1 : What is the detection rank will be for a same inspection method of 15x vs 400x magnification ?
2. Case 2 : What is the detection rank will be for a same inspection method of sampling vs 100% inspection ?

Note : Case1 & 2 are perform by same operator with manual inspection method.

Will detection show the same rank because of same operator with same inspection method ?

 

[Bev D]

snarky response: what do you want it to be?

Seriously, the only way to rate the detection of these approaches is to do the measurement systems analysis correctly. Then you will know.

Any other approach is guessing and science is not a democracy

 

[mlshim88]

Hi,

MSA analysis is to measure the effectiveness of inspection method as well as operator competency.
For this case, operators are competence enough and the method of inspection is proven effective.

Sampling inspection can be defined as a technique to determine the acceptance or rejection of a lot or population on the basis of number of defective parts found in a random sample drawn from the lot. It would expect some level of ppm of defective parts escape to customer. While 100% inspection is performed all units and chances of escape to customer is relatively low.

Whether is using sampling or 100% inspection, it is very much depend on product quality, inspection cost & resources. If the process choose for sampling inspection, the reason could be the process is robustness and less quality issue, and low risk. Whereas if the process is choose for 100% inspection, the process probably is not robust and high defective rate and high risk to customer, that’s why 100% inspection would mitigate the escape risk to customer.

After all, the ultimate goal is to prevent defective unit ship to customer. As such, both sampling or 100% inspection shall achieve the same objective with engineering justification.

Now, it comes back detection ranking …..
The assumption is both sampling and 100% inspection hv gone through engineering justification with proven effective method from competency operator.
Detection ranking shall be same or different ?

The same concept and question to different magnification.

Kindly provide your valuable input.

Thx.

 

[Sebastian]

Looking on Detection table, it seems that frequency of visual inspection is irrelevant to its effectiveness.
Generally we won't find there any word related to frequency, but starting from 4 above (to 1) we may expect "100%".

 

[Bev D]

My first response stands. Guess or do the MSA.
you are misinformed about MSA. It is a lot more than test for “operator competence” or the other things you mention. It has to do with the effectiveness of the entire measurement system.