Product audit is an evaluation and qualification method of a product. To validate whether it is conformed to all specified requirements (both internal and customer), and fulfilling its purpose. Unlike process audits, the product audit analyses the part itself (the result), and not the processes. By which the part was manufactured. During the last decades both product and process audits became complementary methods.
What is product Audit?
Product audit is a testing / inspection / measurement activity, and a major part of Quality Control (QC). A product audit is based on product characteristics, and functionality (e.g. features, specification, drawings, dimensions, packaging, labelling, etc.).
With the increasing volumes of mass production, the industrial sector had to find a solution to validate the manufactured products on a consistent way, and extended the quality control methods. While online testing (that is performed during production) is usually testing or measuring one or a few characteristics of a product in 100%, product audits are covering a wider range of “fit-form-function” tests, and are conducted only on samples, that have been previously accepted or rejected. Some product audits are destructible.
Examples for product audits:
- Heat-shock on 1% of engine control units in a HAST Chamber (Highly Accelerated Stress Test).
- Complete re-measurement of dimensions on 0.1% of the finished product with 3D coordinate measurement machine.
- Special life-time testing and disassembly of pre-launch samples, that won’t be sold.
- Disassembly and complete revision of a vehicle after 50.000 miles.
In the automotive business sector, ISO/TS 16949:2009 mentions product audit as a mandatory element of the system, while VDA even has a separated part (VDA Volume 6 / Part 5) about conducting product audits.
Product audits provide several benefits to the company’s life, such as:
- Continuous feedback and statistics about the product quality.
- Comprehensive testing, or increased level of product audits can detect serial failures and avoid incidents at the customer, by isolating non-conform parts.
- Cost of quality can be decreased (appraisal cost is increased, but unexpected quality incident costs are decreased).
- It provides inputs for continuous quality improvement.
Product audit always has to have an outcome (pass / fail), and a report (test protocol, test report, etc.).
Having product audits is not only a requirement in various standards, but it’s a must if you want to drastically increase your failure detection. No sustainable quality exists without quality control and product audits.
You can properly define your product audit specifications (what to check, how to check and how often), by using your DFMEA, PFMEA, previous experience, and lessons learned principles. The product audit plan (including part numbers, audit frequencies and sample sizes) should be made proactively for every product family for each year.
For example:
- Part name / Part number / Product audit frequency in 2016: 200 ppm.
- New product (safe launch) / Part number / Product audit frequency in 2017: 1.000 ppm for 4 months, 100 ppm from the 5th month.
How would you plan a product audit? On a simple language, let’s make an example. You have to collect all features and functions, based on relevant specifications, industry standards and governmental regulations.
Example: the following form contains the product audit check-list of an SSD (Solid State Drive). It shows raw data about the tested features of the product.
Product Audit Report
| Header Data | |||
| Product name | SSD 512GB Internal | Product audit frequency | 0,5% (5 000 ppm) |
| Part number | AAAA.BBB.CCC-01 | Date of production | Date code: 25012017-14774 |
| Serial number (SNR) | 1122454454 | Date of product audit | 02-04-2017 |
| Part I – shocking the part | |||
| Step | Specification | ||
| Heat shock (non-operating) | -40 oC to +85 oC (200 cycles / 15 minutes per cycle / 10 sec transition time) | ||
| Vibration (non-operating) | 25 – 2000 Hz random / 20 G / 3-axis | ||
| Mechanical shock (non-operating) | 200 G / 3-axis | ||
| PART II. – testing the part after shocking | |||
| Characteristic / Attribute | Specification (LSL – USL) | Measured value | Evaluation |
| Form, size | |||
| Length | 100.0 – 100.2 mm | 100.15 mm | Passed |
| Width | 69.8 – 69.9 mm | 69.87 mm | Passed |
| Height | 6.7 – 6.8 mm | 6.78 mm | Passed |
| Weight | 66.0 – 66.2 g | 66.05 g | Passed |
| SATA Connector | Acc. to connector drawing | All dimensions OK | Passed |
| Function and Performance | |||
| Capacity | 512 GB | 512 GB | Passed |
| Interface speed | 6 Gb/s | 6 Gb/s | Passed |
| Sequential write | 510.0 – 520.0 MB/s | 519.0 MB/s | Passed |
| Sequential read | 530.0 – 550.0 MB/s | 545.0 MB/s | Passed |
| 4KB random write | 89.000 – 90.000 IOPS | 89.750 IOPS | Passed |
| 4KB random read | 99.000 – 100.000 IOPS | 99.400 IOPS | Passed |
| Consumption – write avg. | 2.8 – 3.0 W | 2.96 W | Passed |
| Consumption – read avg. | 2.9 – 3.1 W | 3.05 W | Passed |
| Consumption – sleep | 0.1 – 0.2 W | 0.12 W | Passed |
| Function test on operating temp. | 24h long operation on temperature range of 0 oC to +70 oC | All OK | Passed |
| Packaging | |||
| Packaging | Acc. to pack. spec. | All OK | Passed |
| Labelling | Part Number (P/N), Serial Number (SNR), label size, label position, readable data matrix acc. to spec. | All OK | Passed |
Conclusion
- The product audit is the evaluation and qualification method of a product for being conform to all specified requirements (both internal and customer), and fulfilling its purpose.
- Product audit is a testing / inspection / measurement activity, and a major part of Quality Control (QC).
- The reference of a product audit is always a specified value of an attribute (defined in specifications or on drawings)
- Product audits usually cover most of the products features and attributes, but not conducted in 100% on all parts (e.g. complete validation and measurement on 1% of the products)