This Blog details the usage of sampling schema in process inspection of type 03.

Requirement: There was specific requirement during inprocess inspection to derive the inspection sample quantity based on the inspection lot size. Accordinly the samples are inspected and acceptance or rejection criteria is defined.

Scenario 1: If the lot size quantity is 100 or less, then upto lot size of 100 inspection sample quantity should be 2 quantity and anything beyond 100 quantity then inspection lot sample quantity should be 2% of the inspection lot size.

Scenario 2: If the lot quantity is 500 or less, then upto lot size of 500 inspection sample quantity should be 1% of inspection lot size and anything beyond 500 quantity then inspection lot sample quanity should be 5 quantity.

Approach : This requirement is addressed by defining the sampling schema and assigning the same to sampling procedure. In turn sampling procedure is assigned to inspection plan.

Scenario 1: Step followed are given below:

  1. Creation of Sampling Schema
  2. Creation of Sampling Procedure
  3. Assigning Master Inspection Characteristics /Sampling procedure in Routing
  4. Sample Size in inspection lot

Step 1: Creation of Sampling Schema: ( Tcode : QDP1)

Sampling plays an important role to derive the number of samples to be inspected based on the inspection lot size.

Enter the sampling schema name and its text. Select Attributive insp under Valuation Parameters and Severity/AQL under Sampling tables for as displayed below.

SC1.png

On enter system pop up another screen to enter the Insp severity and AQL value. Select Insp severity as 004 -Normal Inspection and AQL value as 2. AQL value is the maximum number of defects. Since as per scenario 1 we require 2 samples if the lot size is less than or equal to 100.

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Click on choose, then system will display the below screen to maintain the lot size and sample quantity.

If lot size is 100 or less then sample size is maintained as 2.

If lot size is 150 then sample size = 150 * 2 % = 3. Like wise lot size and sample size is defined below upto the maximun lot size used by business.

on SAVE sampling schema S2% is created in system.

SC3.png

Step 2: Creation of Sampling Procedure: ( Tcode : QDV1)

Enter the sampling procedure name, text and select Sampling type as Use sampling schema and valuation mode as Valuation according to char attrib.code as displayed below. Since inspection are not used Radio button without inspection points selected.

SC4.png

Click on continue and maintain the sampling schema S2% as displayed below.

SC5.png

Click on addtional data and select the inspec severity and AQL Value as displayed below.

SC6.png

System will display the below message, click on yes. Sampling procedure will be created.

SC7.png

Step 3: Assign MIC and Sampling procedure in Routing ( Tcode : CA02)

MIC assigned for operation 0030 along with sampling procedure SP-2%.

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Step 4: Sample Size generated (QA02)

Case1 : Production Order and Inspection lot size is 50. Sample qty generated is 2 as per sampling schema lot size 100 and below sample size should be 2. Below screen shot displays the sample size.

SC1.png

Case2 : Production Order and Inspection lot size is 100. Sample qty generated is 2 as per sampling schema lot size 100 and below sample size should be 2. Below screen shot displays the sample size.

SC2.png

Case3 : Production Order and Inspection lot size is 120. Sample qty generated is 3 as per sampling schema lot size 100 and above sample size should be 2% of lot size. As per sampling schema from lot size above 100 to 150 sample qty should be 3. Hence system generated sample size of 3.

SC3.png

Similarly for lot size 150 given below.

SC4.png

Similarly for lot size 200.

SC5.png

Scenario 2: If the lot quantity is 500 or less, then upto lot size of 500 inspection sample quantity should be 1% of inspection lot size and anything beyond 500 quantity then inspection lot sample quanity should be 5 quantity.

Here sampling schema to be defined such that upto 500 qty sample size should be derived based on % and beyond 500 it should be constant number.

Sampling Schema defined as shown below and assigned to sampling procedure.

SC0.png

Case 1: Order created for 200 qty and inspection lot generated for 200 qty. Based on the schema sample size generated for 2 qty as displayed below.

SC0.png

Case 2: Order created for 600 qty and inspection lot generated for 600 qty. Based on the schema sample size generated for 5 qty as displayed below.

SC0.png

Conclusion:  With the usage of sampling schema required sample  size can be derived based on the order lot size. Suitable for process where acceptance/rejection of the entire lot is based on no of the samples tested and their results. In such case deriving the sample size considering order lot size plays important role. Deriving the correct sample size can be achieved through usage of sampling schema.

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2 Comments

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  1. Martin Hinderer

    Hello Rao,

    I just ran over your document today, and I found some unclear things in your document:

    If you do sampling based on ISO 2859-1:2014-08(you did not mention that exactly), then there is no AQL of 2 defined.

    The AQL also does not state the maximum number of defects. Please check ISO 2859-1 for the correct definition. In your examples I am not sure if you should use AQL at all (why don’t you just use “insp. severities” in your sampling scheme?).

    Your presented sampling schemes imply that you have only inspection lots of the defined lot sizes. You did e.g.. defined samples for 200, 250, … lot sizes. If you exactly hit these sizes, then your statement “if greater than 150, use 2%” is correct. If you have e.g. a lot size of 225, then it is not.

    Best regards

    MH

    (0) 

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