Manufacturers in the United States employ more than 8.5 percent of the total workforce and account for over 10 percent of the country’s gross domestic product (GDP). As the scale of manufacturing ramps up, however, so does regulatory oversight to ensure that products produced meet standards such as the ISO 2859-1 acceptance quality limit (AQL). Failure to do so can result in significant consequences: In 2021, the car manufacturer Toyota agreed to pay a record $180 million fine for producing vehicles with faulty emission-control components. To help avoid this issue, manufacturers benefit from a focus on continual quality assessment and improvement. One way to achieve this goal is by using a layered process audit (LPA) — here’s what that looks like in practice.
What is a Layered Process Audit?
A layered process audit system focuses on frequent and ongoing assessment of existing processes to pinpoint potential issues and identify opportunities for improvement. Often used in the automotive industry by original equipment manufacturers (OEMs), these audits focus on improving current standards or processes rather than examining finished goods or defective products. While the evaluation of finished products for defects is also a critical aspect of quality control, LPAs look to reduce the number of defects by identifying and remediating their root causes.
These audits can help companies achieve AQL goals and reduce the number of product batches that must be rejected. Consider a production run of 1,000 units with an AQL of 1 percent or 10 units. This means that if 11 units are defective, the entire run must be rejected. LPAs look to find processes that are negatively impacting AQL and adjust or eliminate them to ensure that quality standards are satisfied.
Unpacking the Layers of a Process Audit
An LPA program typically has three layers which correspond to different layers of management personnel responsible for conducting audits.
Layer 1 refers to shop floor supervisors and production line team leaders who conduct high-risk process audits daily and across every shift. Layer 1 audits help identify patterns of behavior or operation that could be negatively impacting overall quality.
Layer 2 includes various levels of middle management staff who typically conduct audits once or twice a week. Using feedback from layer 1 auditors along with their assessment of processes, layer 2 personnel help prioritize larger-scale issues.
Layer 3 brings in-plant managers to conduct audits monthly and executives who may audit processes once per quarter or once per year. Combining the feedback of previous layers, this final LPA layer looks to ensure that process changes have been implemented and identify areas where more improvements are needed to address quality issues to create robust control plans defined by clear metrics.
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Making the Most of Your LPA Process
To ensure your LPA system delivers desired process quality improvements, three factors are critical:
- Effective issue identification
To improve quality processes, companies must first identify key issues. While it’s possible to build your own LPA evaluation criteria from scratch, purpose-built solutions can help address issues in quality management systems (QMS) and environmental management systems (EMS), respectively.
- Clear communication
Once issues have been identified, companies need clear communication to ensure staff members are fully informed of process control roadblocks and understand the need for improvement. Here, the goal isn’t placing blame but working together to create processes and preventative actions that both reduce defect rates and make production lines more efficient.
- Quick corrective action
Finally, companies must take follow-up corrective action in as close to real-time as possible. Simply identifying issues isn’t enough; all three audit layers must work together to define a solution, implement it, and document the results. This is especially critical as manufacturing processes evolve; what solves a problem one month may not be sufficient the next — as a result, continued LPAs are critical.
Bottom line? Layered process audits are part of the cost of quality. Implemented effectively, they can help pinpoint issues to help companies reduce total defects, enhance product quality, and improve production line performance.
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