Query in Classed recording in MIC

[former_member220469]

Dear Experts,

I am trying to explore the feature "Classed recording" for an Quantitative MIC. I referred QM expert Craig's earlier post on classed recording topic. But i am having fundamental doubts in this topic.

I have created a Quantitative MIC with the below data

Lower spec. limit - 29 mm

Upper spec. limit - 31 mm

Target spec. limit - 30 mm

No of classes -      2

Class width -         0.5mm

Class midpoint -    30 mm

I have assigned the MIC in inspection plan and i have created the Inspection lot for the lot qty of 30 Ea with inspection type 89. While performing the result recording for the inspection plan the below

Class	Lower Class limit	Upper class limit	Class size	Valuation
1	14.5	29.5		Rejected
2	29.5	30		Accepted
3	30	30.5		Accepted
4	30.5	62		Rejected

But i was expecting only 3 class will be created as given below.. Is my understanding is correct?

Class	Lower Class limit	Upper class limit	Class size	Valuation
1	29	29.5
2	29.5	30
3	30	30.5

My queries are given below

1. How the Lower class limit for class 1 is calculated as 14.5 ?

2. How the Upper class limit for class 4 is calculated as 62?

3. How the Valution is showing automatically as "Accepted" and "Rejected"?

4. How to update the results for this scenario in column "Class size" ?

Please provide your inputs for my understanding on this issue

[former_member42743 · Accepted solution]

I'd suggest increasing the number of classes to 4.

[former_member220469 · Accepted solution]

Dear Anand , Craig,

Thank you for your excellent explanation. I understood the concept of classed characteristic with Tolerance values,Class width, class midpoint. But i am unable to understand the usage of Plausibility in this process. I tried understanding with F1 help but i couldnt get it. It would be grateful if you can explain the usage of the Plausibility and below fields in the classed characteristic process

Lower Plausibility Limit

Upper Plausibility Limit

Change to Lower Specification Limit

Change to Upper Specification Limit

First and second Lower Specification Limit

First and Second Upper Specification Limit

J.Balakrishnan

[former_member42743 · Accepted solution]

In classed results you need to account for all possible values.  While you might not expect to record a value out of spec, (i.e. below 29 or above 31 in your example), it is physically possible to have a result of say 28.  Where would you have expected to put that one if the only classes you had were 29.0 - 30.5 as shown in your second table?    

BTW: In your table of expected classes where would a result of 30.8 go?  And if you have a class width of .5 but your spec has a width of 29-31 (a full 2 mm range) how can you expect to have only two classes of a .5 width?

First and second specification limts only come into play for SPC characteristics and are used for action limts.  Otherwise in SAP they are just there.

The upper and lower plausibility limits are usually meant to be the limts of the test.  I.e. tests measered in % usaully have plausibility limts of 0% and 100%.

Craig

[former_member220469 · Accepted solution]

Hi Craig,                                                                                                                        Thank you. But i am still struggling to understand the usage and how the plausibility limits play a role in valuating an inspection. It would be grateful if u can explain with an simple example

[former_member220469 · Accepted solution]

Hi craig, and anand ,  I understood this functionality. Thanks a lot. Points rewarded

[former_member42743 · Accepted solution]

In classed characteristics the plausibility limits should have no affect on the test.  In fact, none of the specs really do. They are just used to determine the class groupings.  They are normally used for quantitative characteristics to prevent absurd, fat fingered entries into a result.

For the classed characteristics, the plausibility limits are just used as the boundary values to display to the person recording the result, what are the allowed values for that particular class.  A value below the lower spec is allowed, (otherwise how would you note an out-of-spec value?).  But at some point, the value can become so absurd that the result is impossible.

Example: PH

Test range is 0 - 14.

One decimal

For a classed characteristics you might have a spec of 7.8 - 8.6, class width of .2, number of classes 6, midpoint 8.2.  Your classes should be as follows.

0 - 7.8

7.8 - 8.0

8.1 - 8.2

8.2 - 8.4

8.4 - 8.6

8.6 - 14

But.. for a given material, anything over 10 would destroy the equipment and anything below 5 is pretty likely to never happen.  Make the plausibility limits as 5.0 and 10.0.  The classes should now be like:

5.0 - 7.8

7.8 - 8.0

8.1 - 8.2

8.2 - 8.4

8.4 - 8.6

8.6 - 10.0

In a classed characteristic all it does is change what is displayed for ranges.  If it was a true quantitative characteristic,  any values above 10 or below 5.0 should give another warning to the user that the value entered exceeds the plausibility limits.  The value can still be recorded but the user has to acknowledge that warning and SHOULD be checking to make sure the result is really valid.

Craig

[anand_rao3]

I try to answer these!

1. The value 14.5 is basically Lower plausibility limit and is calculated based on the the value that you put in Plausibility factor (%) in QM plant level customization under Result Recording tab. It must be 200 maintained there! Considering that as 200%, 14.5 is calculated as Lower Limit/2 = 29/2 in this case.
2. Similarly it doubles the upper plausibility limit with respect to upper limit. So here it is 31x2=62
3. The reason for showing valuation is the class range. The range 14 mm to 29.5 mm falls out side tolerance limit of (29 mm to 30 mm). And hence it is default Rejected
4. The range 30.5 mm to 62 mm falls out side tolerance limit of (29 mm to 30 mm). And hence it is also default Rejected.
5. Classed recording is different that the individual recording. Here instead of putting individual reading you enter how many samples you found in that class range.
6. If you sample size is 10, then you have just to enter how many out of 10 you found in those specific class range. If you found 2 samples with reading 27 mm and 28 mm you should put 2 against the class 14.5 to 29.5 and not the actual reading. And as said earlier this class is rejected.

Anand

[busyaban7]

Thanks Anand !!