Published: 10 Nov 2021

Layered process audits have long been established in the automotive industry, but they can also play a key role in improving quality standards across a range of other sectors, says Ravindiran Gurusamy, an IRCA Certificated Associate Auditor.

Of the four key goals driving quality management systems in the automotive sector, preventing defects is the most critical.

Of course, the other three goals – continual improvement; reducing variation; and waste in supply chain – are all important. However, if an organisation is forced to minimise its focus on them temporarily, it should still be able to maintain its current performance levels.

By contrast, a defect in the process poses an immediate and potentially critical risk to the business and its customers.

Individual organisations can follow different types of defect prevention methodology based on their understanding and capability – and layered process audits (LPAs) can hold the key to success.

What are layered process audits (LPAs)?

Eric Stoop has described an LPA as “a quality technique that focuses on observing and verifying how products are made during the manufacturing process, rather than inspecting the finished item. They are not confined to the quality department but involve people at all levels of the organisation”.

It is not only companies in the automotive sector that can benefit from an LPA. It is a management tool that can be used by any organisation that is conforming to its relevant management system standards. The process provides an opportunity to emphasise the importance of those standards to the whole organisation – and thereby identify opportunities to reduce defects and improve overall performance.

Cross-functional involvement

As the name implies, people involved at multiple layers across the organisation take part in an LPA. LPAs are not conducted by trained auditors or by team members who are normally involved in that particular manufacturing process. Instead, personnel ranging from junior factory workers to those in the highest levels of the organisation can get involved. Since these people are often new and unfamiliar to the process, they can demonstrate impartiality, objectivity and fresh insight into how it is working or how it should work. If anything, this might be better described as verification rather than audit.

If senior leaders are seen to be engaged in LPAs and thereby create a sense of shared ownership, employees at all levels will have much greater confidence in the process
Ravindiran Gurusamy

The automotive QMS mandates that, when the particular process or process control is in contingency mode due to failure of the originally planned facilities or the failure of planned process control equipment, the organisation shall follow the layered process audit to ensure the outputs are meeting the standards required. 

Inputs to an LPA can be taken from relevant criteria and key performance indicators (KPIs) including but not limited to: customer-specific requirements; risk documents; statistical techniques; and trend charts relating to factors such as rejections, rework, low first-time pass and run rates, manufacturing down time, accidents and customer complaints.

Maximising the benefits

To achieve the maximum benefits from LPAs, I believe organisations should adopt the Pareto (80:20) principle, which states that roughly 80% of consequences come from 20% of causes. So the priority needs to be about focusing on defects according to the following three criteria: highest severity; highest frequency of occurrence; and lowest detection level.

There are many benefits that can be achieved via effective implementation of LPAs. These include, but are not limited to:

  • Better communication between senior management and line associates
  • First-hand feedback
  • Reduction of safety incidents
  • Minimisation of waste
  • Better cashflow
  • Enhanced customer satisfaction by improving product quality
  • Reducing scrap, rework and other consequences of poor quality
  • Reducing recalls, warranty and dissatisfaction
  • Enabling management to take considered investment decisions
  • Continual improvements.

Keys to success

So how can we make sure these benefits are realised? In my opinion, there are three critical success factors for LPAs. 

  1. The first is that senior management should support and buy into the process. If senior leaders are seen to be engaged in LPAs and thereby create a sense of shared ownership, employees at all levels will have much greater confidence in the process. 
  2. Second, communication across the organisation needs to be clear and honest. For example, teams need to understand the difference between fact-finding and fault-finding: LPA is as much about finding out the facts about the critical processes, as it is about uncovering the faults.  
  3. Finally, it’s important to ensure that the audits have genuine impact, as demonstrated by the following case study.

CASE STUDY: LPA in action

A machining supplier to an automotive original equipment manufacturer (OEM) was carrying out multi-drilling using a dry cutting process with a cast iron component.

To improve productivity, the organisation replaced the existing two spindle machines with six spindles. Issues faced included:

  • Heavy dust generation
  • High noise levels – more than 105dB(A)
  • Less tool life – 70 to 80 cycles per resharpening
  • High level of rejections – more than 10,000ppm.

So the organisation started implementing a layered process audit (LPA), involving other process engineers and people from different parts of the organisation, including the senior manager. Regular reviews were carried out by top management and the entire team, including the operators.

After three cycles of LPAs and reviews, senior management decided to trial using a wet cutting process instead of a dry cutting one. This led to immediate benefits including:

  • No dust generation
  • Noise levels reduced to 85-87 dB(A)
  • Tool life extended to 450 to 500 cycles per resharpening
  • Rejection reduced to 100ppm.

When the process was changed permanently, results continued to be positive and the morale of the team also improved considerably.