With good planning, an organization can use test and inspection as a tool for competitive advantage. The following will illustrate how this works in an automotive environment; however, the concepts easily generalize to any industry.
During product development in many industries, some type of development, or launch, process occurs. One hypothetical, generic model for such a launch process might look like the following:
- System level
- Preliminary design
- Critical design
- Test readiness
- Production readiness
Types of Tests During DevelopmentA variety of approaches provide reasonable coverage as one attempts to uncover any significant product or process issues. Some of these types of testing include compliance testing to specification requirements; extreme testing to produce product damage as well as characterize the product; combinatorial testing to check all inputs against all outputs; and stochastic, or exploratory, testing to randomize test inputs.
When Does Inspection Begin?One of the nice things about inspection is that it is typically nondestructive. While a small sample of product under extreme testing is often studied, large quantities and samples of product will need to be inspected. A product or process can be inspected as soon as there is something to look at. During product development, the following can be analyzed:
- Design (HW/SW) and schematic reviews
- Computer-aided design (CAD) modules
- Prototype parts
- Review process
- Bill of materials (BOM)
Types of Inspection During DevelopmentA bill of materials verification is used to compare the product with the drawings and with the bill itself. This type of inspection is usually tedious; however, we know that a BOM should be better than 98% accurate to support the manufacturing resources planning (MRP) system accurately. Additionally, traceability matrices can be used to verify product or process against the specification. Checklists at any phase of the process ensure that tasks have been completed. One also can inspect design guidance documents for compliance and perform some level of attribute requirements checking.
In the automotive world, the accuracy of machines, processes and employees is studied with gage repeatability and reproducibility (GR&R) inspections. Accurate templates and measuring instruments as well as determining individual impacts on measurements will enhance the performance of a manufacturing process.
Test, Inspection & Evaluation Master Plan Operations (TIEMPO)Test, Inspection and Evaluation Master Plan Operations (TIEMPO) expand the concept of a test and evaluation master plan by focusing on staged deliveries of which product or process release is a superset of the previous release, and the test and inspection iterations are coordinated with releases. Under this plan, the following inspections can be handled:
- Code reviews
- Code releases
- Design reviews
- Schematic reviews
- Reduced risk
- Identification of early activities to secure quality-even before testing can take place
- Test and design release iterations planned-test tools and test processes developed in time to test
- Frequent customer access for review of product evolution
One Industry Approach: Automotive/VehicularThe standard approach in the vehicular industries is the advanced product quality planning (APQP) mode of the Automotive Industry Action Group (AIAG). The components of this approach are the concept, product development, process development, verification and validation, and feedback and corrective action-each with its own set of steps and input and outputs.
Failure Mode Effects Analysis (FMEA)Two automotive tools that illustrate the connection between inspection and testing are Design Failure Mode Effects Analysis (DFMEA) and Process Failure Mode Effects Analysis (PFMEA). The tools facilitate critical reviews of either the design or the processes that produce the designed product (production processes). This tool critiques a particular design or process function using failure modes, causes, effects and some estimated values.
The Risk Priority Number (RPN) is the product of estimation of the severity, probability and detection of a particular failure. The higher the RPN, the greater the risk to the product design or process. Recommended actions often are testing actions to determine if the estimates of severity, probability and detection are valid or to determine another way to achieve the function. In any case, the results of the DFMEA or PFMEA have an impact on the design verification testing (DVT) and production validation testing (PVT).
In the automotive world, DVT means using prototype parts, prototype tooling, an unfinished production process and maybe even handmade parts. The purpose of DVT is to test out and verify design ideas before proceeding with development.
Again, in the automotive world, PVT means using production software, production components, production tooling, the final production process and production information systems. The goal of PVT is to verify that product is manufactured correctly using a real production line.
Reliability TestingReliability testing assesses the probable quality behavior of the product or process during some quantum of time. During reliability testing, small sample sizes are used when a baseline exists, as well as with larger sample sizes with no baseline. Physical models for accelerated testing are used in order to compute probable product life, which can be hampered by lack of good models, especially when a baseline does not exist.
The Production Part Approval Process (PPAP) and InspectionAPQP supports multiple inspection points such as bill of materials checks against parts and drawings, appearance approval and the various review processes.
By definition, an inspection is a form of quality containment-trapping the product or process that does not truly break the chain of cause and effect. The function of inspection, then, is to capture bad material and to stimulate meaningful corrective actions.
In the automotive approach, there are at least 18 items that must be provided to the customer. The list includes the following:
- Design Records
- Authorized Engineering Change
- Engineering Approval
- Process Flow Diagrama
- Control Plan
- Measurement System Analysis Studies (MSA)
- Dimensional Results
- Records of Material / Performance Tests
- Initial Process Studies
- Qualified Laboratory Documentation
- Appearance Approval Report
- Sample Production Parts with pictures
- Master Sample with signoff
- Checking Aids
- Customer Specific Requirements
- Part Submission Warrant (PSW)