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Example documentationExample: How Sampling Works

 

During production, engine mounts are welded and then sent to an ASSEMBLY operation. To control the quality of welding process, sampling operation is set up between the WELDING and ASSEMBLY operations. At the SAMPLING operation, 5 mounts are randomly selected from every group of 25 pieces and sent to the nondestructive weld test. If two or more mounts fail the test, then all mounts in the group are sent to the test for 100% inspection.

Prerequisites

  1. The following routings are created in Routing Maintenance:

    • Routing for production with the operations WELDING, SAMPLING, and ASSEMBLY

    • Routing for sample inspection

      Sample inspection routing is of the Sampling type and contains one test operation (NDT) and two possible dispositions: returning to the next production operation (ASSEMBLY) and scrapping the tested piece.

      Note Note

      The scrap itself does not mean the SFC number fails the test. Only the total severity of logged NC codes defines if the SFC group is accepted or rejected.

      End of the note.
  2. NC codes to be used during the NDT test operation are defined in NC Code Maintenance. NC code that is used to indicate test failure is set up with the high severity. The code that indicates the minor defect and is not intended to influence the accept/reject decision significantly is set up with the low severity.

    Note Note

    If the operator logs many NC codes with the low severity, SFC number can still be rejected. This is because the severity values of all logged NC codes are summarized and compared to the defined threshold. If you want the minor defect never fail the test, set up the NC severity for the code to None.

    End of the note.
  3. Sample plan that defines sampling characteristics is set up in Sample Plan Maintenance. Selection of sample plan type depends on whether you need your sampling to confirm to the American National Standard (ANSI Standard).

    • On the Main tab page, sampling routing and NC severity threshold are defined. NC severity threshold is used to compare the total severity of logged NC codes to define SFC group accept/reject decision. Here you can also indicate whether the operator can skip sampling of the group and what message to send in this case. Additionally, a message to be sent to the message board when sample group is rejected is defined here.

    • On the Details tab page, the SFC Group Size value is set to 25, the Inspection Level Procedure value is set to General, and the Acceptance Quality Limit value is set to 10. Depending on these values, the system calculates the sample size value (5), accept (1) and reject (2) numbers according to the American National Standard for the sample plan of the ANSI type.

      Note Note

      If sample plan is of Custom type, the user can enter the accept/reject numbers and sample size directly. In this case, the system will not check if the values conform to any standard.

      End of the note.
    • On the Attachment tab page, define the material and the operation at which sampling shall take place. In this example, SFC numbers of ENGINE_MOUNT material are sampled at the SAMPLING operation.

  4. PODs required for sampling are configured in POD Maintenance. For this example, you can configure four PODs, one for each operation. Another option is to configure one POD to be used at all operations.

    • For the sampling operation, configure a button (PASS) with three activities attached to perform start (PR500), complete (PR510) and sampling (QM020) of SFC numbers.

      Recommendation Recommendation

      We also recommend that you configure a separate button, with only the Perform Sampling (QM020) activity. It can be used for opening Perform Sampling plug-in if there are enough SFC numbers in the group. This may be useful if an operator has closed the plug-in previously without confirming the sampling and wants to open the plug-in again to perform it.

      End of the recommendation.

      On the Layouts tab page, the layout for the Perform Sampling (QM020) activity is required to be defined. For example, you can define this activity as the Other Plug-In to substitute it for the default one (for example, Work List) in POD.

    • For other operations of production routing, you can use the standard Operation or Work Center POD configurations.

  5. SFC numbers are released for processing on the production routing. Quantity of SFC numbers in queue on the first step of the routing is equal to or greater than SFC group size defined in the sample plan (in this example, 25).

Process

Performing Sampling

Proceed as follows to perform sampling:

  1. Start, perform work, and complete 25 SFC numbers on the first production operation (WELDING). All 25 engine mounts are moved to the next operation (SAMPLING) for sampling.

  2. On the sampling operation, select 25 SFC numbers and perform start, complete, and sampling using the single button (PASS) defined in POD. The system randomly selects 5 mounts out of 25 pieces and displays them to you.

  3. Take these 5 pieces for testing and press the OK button to confirm the sampling. 5 sample SFC numbers are moved to the NDT operation for a nondestructive test. Other 20 SFC numbers remain on the sampling operation (SAMPLING) until the test results are known.

Inspecting the Sample

Proceed as follows to inspect the sample:

  1. On the first operation of the sampling routing (NDT), start 5 SFC numbers you have in queue and perform the test.

  2. If the engine mount passes the test, complete it. At this point you can indicate whether this SFC number shall go to the assembly operation (ASSEMBLY) or shall be scrapped. If the test is nondestructive and SFC number successfully passes it, select to send it to the next operation.

  3. Choose the next SFC number and perform the test. If the SFC number fails the test, log the test failure NC code against it. As this NC code indicates the test failure, it must be setup with a high severity. In this case, when you press Done in the Log NC plug-in and select whether to scrap this SFC number or send it to the ASSEMBLY operation, this SFC number will be rejected.

    Note Note

    You can check the result of sample inspection in SFC Group Report at any point. To view this information, select the material and/or operation in the SFC Group Report. You will see all the SFC groups that have been created for engine mount inspection. Against the current SFC group you will see that 2 SFC numbers have already been inspected: one of them passed the test and another one failed. If in your setup one failure is considered acceptable, the SFC group is still in the Sampling status. This means that the sample inspection result for the SFC group is not known at this point. If all the remaining SFC numbers will pass the inspection, the group will be accepted. But if at least one more SFC number fails the test, the whole SFC group will be rejected and passed to 100% inspection.

    End of the note.
  4. Start and examine the next SFC number as passing the test. If you see a minor defect that does not cause the test failure, log an NC code with low severity. This will indicate that there is a minor issue but the welding quality is acceptable and SFC number can proceed to assembly. Complete the SFC number.

    Note Note

    An NC code with low severity does not exceed the severity threshold, that is why the SFC number is accepted. You can see this in the SFC Group Report.

    End of the note.
  5. Start, test and complete the remaining SFC numbers. Now the whole SFC group is accepted and all SFC numbers waiting for the group inspection result at the sampling operation (SAMPLING) are moved to the next operation on the production routing (ASSEMBLY).

    Note Note

    When the group is rejected, the SFCs are dispositioned differently. In this case, all the engine mounts waiting on the sampling operation are moved to NDT test operation for the 100% inspection.

    End of the note.

The figure below illustrates the primary flow of the engine mounts sampling described above: