This blog reviews how to utilize statistical process control, process validation, and supplier auditing to qualify suppliers effectively.
If you could afford to audition suppliers for a few months against hundreds of other competitors, then only the qualified suppliers would be approved. Unfortunately, you don’t have the same budget that American Idol has. So what should you do instead?
Most companies use the same three, tired tools to qualify suppliers: ISO Certification, Quality Manuals, and questionnaires. ISO certification is a weak tool because certification is only as good as the registrar’s worst client. Quality Manuals are intended to define the intent of your supplier’s Quality Management System, while most of the details are located in procedures. You only need a copy of your supplier’s Quality Manual to help you plan audits. Supplier questionnaires seem to be the most popular tool, but most of the questions require a “Yes/No” response that suppliers rarely answer negatively. To assess the qualifications of potential suppliers more effectively, try using the following tools instead:
Tool # 1: Statistical Process Control
Most companies require a Certificate of Compliance (CoC) with every shipment. A CoC is useless. Just like the “Yes/No” responses to questionnaires, you will never see a CoC that indicates something is wrong. A Certificate of Analysis (CoA) is much more useful, because the CoA has actual data, and the tolerance range is typically indicated for each test or measurement that was performed by the supplier. The best report you can get from a supplier is a statistical analysis of each specification during the prototype production lot. When you have a Statistical Process Control (SPC) run chart, you know quantitatively if the supplier is capable of making an acceptable product. The run chart can also be used to develop an appropriate sampling plan for incoming inspection.
Tool # 2: Process Validation
Process validation is much more than determining if a process is capable of producing a consistent product. An SPC run chart can do that. Process validation tells you what range of operating parameters will produce a consistent product. Therefore, when you have process deviations or measurement devices are slightly out-of-calibration, you will know if your supplier’s process will still make an acceptable product. The validation of a process should also identify which variables are critical indicators of the process. This information can be used to reduce the number of variables and specifications that are monitored for a production process, and focus both your supplier’s resources and your own.
Tool # 3: Supplier Auditing
A multi-disciplinary team audit of a potential supplier is an effective tool for assessing a supplier’s qualifications and will help build a stronger relationship between your team and the supplier’s team. Before you conduct an audit, it is important to plan the audit to ensure you get the greatest possible value. The following recommendations are important to supplier auditing:
- Use a risk-based approach to auditing suppliers (this goes beyond just critical and non-critical)
- Strategically select auditors and train them well
- Plan the auditing goals and objectives for the team in advance
- Create a formal audit agenda that defines which processes each auditor will be focusing on
Auditing 100% of your critical suppliers may seem impossible, due to limited resources, but have you ever seen a cost/benefit analysis?
What’s the cost of rejects, rework, and product redesign?
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