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Collecting SPC Data

Statistical Process Control (SPC) data refers to numeric measurements collected from Characteristics of the Parts you produce. SPC data is sometimes called variable or continuous data because it represents continuous variables like length, width, or weight.

This guide builds on GS's Core Concepts and the Getting Started with Inspections guide.

Principles

When collecting SPC data, keep the following principles in mind:

  • The SPC Test is the only Test used to store SPC data.
  • An SPC Test requires a Characteristic to be set before it can accept measurements. This can be done statically, dynamically, or through a script.
  • Although SPC data is stored with a Part, the Part is automatically inferred from the Characteristic assigned to the SPC Test. You cannot override the Part associated with SPC data using a Part Test or script.
  • A Process must be defined for SPC data. This is typically set using the Inspection's Process setting or a Process Test.
  • If you plan to assign the Characteristic of an SPC Test through a script, set the Test's Characteristic Match Method to Static Characteristic and leave the Characteristic field blank.

Static Inspections

The simplest use case is collecting SPC data for a known, unchanging Characteristic. To set up an Inspection for a static Characteristic:

  1. Add an SPC Test to a Sub-Inspection.
  2. Set the Test's Characteristic Match Method to Static Characteristic.
  3. Select the Test's Characteristic.

An image showing the Characteristic Match Method and Characteristic properties of an SPC Test

Dynamic Inspections

In this section, you will create a dynamic, no-code Inspection where SPC Tests automatically select the correct Characteristic based on the selected Part. This approach is useful for shared Inspection layouts across multiple similar Parts.

Setup

Begin by creating two Parts with similar Characteristics.

  1. Navigate to the Parts list page and click Add.
  2. Name the Part 3" Bolt and click Save.
  3. Create another Part named 5" Bolt.
  4. Find the 3" Bolt in the table of Parts and click View.
  5. In the Characteristics section, click Add to create a new Characteristic.
  6. Set up the Characteristic:
    1. Name it Length.
    2. In the Tag section, click Autofill.
    3. Set the Subgroup Size to 1.
    4. Select the Inch unit of measure.
  7. Repeat these steps to create a Width Characteristic of the 3" Bolt.
  8. Repeat these steps to create Length and Width Characteristics of the 5" Bolt.
  9. On the 5" Bolt only, create a Thread Count Characteristic with a Count unit of measure.

Your Parts should now resemble the following images.

An image showing the Characteristics and Tags of the 3" Bolt

An image showing the Characteristics and Tags of the 5" Bolt

Create the Inspection

  1. Navigate to the Inspection list.
  2. Press the Add button. An image showing the location of the Add button on the Inspection list
  3. Fill in the Name field with Dynamic SPC Inspection.
  4. Press the Save button. An image showing the Inspection create form
  5. Add a Part Test.
  6. Add three SPC Tests. For each SPC Test:
    1. Set the Test's Characteristic Match Method property to Match by Part and Tag.
    2. Select the Tags Length, Width, and Thread Count respectively. An image showing a sub-inspection with three SPC Tests and a Part Test
  7. Select the Save and Run action.

Run the Inspection

  1. Run the Sub-Inspection with the Tests. Initially, only the Part Test appears.
    1. This is because the SPC Tests do not yet have a Characteristic set on them. They require a Part to determine their Characteristic. An image showing a running sub-inspection with only a Part Test
  2. Select 3" Bolt in the Part Test. Notice that the Length and Width SPC Tests appear.
    1. This is because the 3" Bolt has Characteristics with Length and Width Tags.
    2. The Thread Count SPC Test does not appear because the 3" Bolt does not have any Characteristics with the Thread Count Tag. An image showing a running sub-inspection with a Part Test and the 3" Bolt SPC Tests
  3. Enter values for Length and Width, then click Submit.
  4. Rerun the Sub-Inspection and select the 5" Bolt. Notice that all three SPC Tests appear.
    1. This is because the 5" Bolt has Characteristics with Length, Width, and Thread Count Tags. An image showing a running sub-inspection with a Part Test and the 5" Bolt SPC Tests
  5. Flip back and forth a few times between the two bolts. Notice that the SPC Tests change their visibility based on the selected Part.

Summary

By tagging Characteristics consistently across Parts and using the Match by Part and Tag setting, you can build dynamic, no-code Inspections which work across similar products.

See Also