The Toyota Production System recognizes that managing quality is as important as managing just-in-time strategies in a Lean Manufacturing philosophy.
Quality management topics like Six Sigma, DMAIC, and Jidoka are important in the context of Lean Manufacturing because the ultimate goal is to eliminate waste in the value stream and one of the most common types of waste is the correction waste. Correction waste happens when it is necessary to work around poor quality in components or material from suppliers or it is necessary to repair, rework or scrap defective product units.
Quality management starts in product and process design. Concepts like Poka-yoke and Jidoka stress that the design of a product and process should eliminate the probability of error whenever possible, making the correct process visually obvious, and making any errors immediately visually obvious. Standardization, visual work instructions, and automated inspection are some of the tools used to minimize the potential for errors.
Six Sigma techniques and strategies are widely used in conjunction with Lean Manufacturing initiatives to help eliminate waste attributed to poor quality by providing the tools to focus on the right problems, diagnose the right root-cause of issues, and apply corrective action as quickly as possible. Six Sigma methodology uses statistical tools to systematically analyze processes and reduce process variations leading to better quality and performance.
Quality management requirements could be viewed by some as creating a burden of cost and time on the manufacturing process. The potential burden on the overall value stream should be a considered, but more importantly we should continually stress the benefits of predictable consistent quality to the entire team and identify the cost of poor quality to the overall performance of the organization.
Automation in inspection, record keeping, and verification steps can relieve some of the burden of quality processes. Automation is also a double bonus because every time we can take some manual clerical steps out of the process, we are not only cutting down cycle time and labor, but we are also eliminating potential points of human error in the equation.
Statistical Process Control (SPC) techniques including control and process capability charts conduct data and process analysis to understand, detect, and control variation, change, inefficiencies, and deficiencies. When a process shows variation with an unexpected, non‐random pattern, such as a shift, trend, or cycle, the process is unstable and unpredictable, or it is out of control. Out-of-control processes are wasteful processes that because they will produce unacceptable amounts of defective product or scrap material.
Workflow and rule engines, like the ones enforcing the Western Electric rules in SPC, can automate analysis in the background and alert assigned personnel automatically based on defined rules that are consistently implemented by the system. Automation can be viewed as a sidekick that is performing analysis on the side and bringing to the attention of the operator any out of control condition as soon as it is detected.
Statistical sampling and auditing methodologies allow us to further reduce the cost of inspection procedures by providing the appropriate quality confidence level with less than 100% inspection requirements. Automated data collection and statistical software tools are able to continuously monitor multiple processes and increase oversight as needed on suppliers and internal processes that are falling out of normal parameters. These tools greatly decrease overhead when compared to other traditional manual oversight methodologies.
Another aspect of Toyota’s Lean and Jidoka philosophy is a culture of stopping to fix problems right away--the earlier the better. In order to do this we need (1) tools to help us achieve quality the first time, (2) tools to monitor processes that are susceptible to variables like environmental conditions, material variances, equipment wear and tear, or operator training, and (3) an efficient corrective action process.
Quality metrics are as important as throughput, cycle-time and schedule adherence metrics in our overall assessment of a Lean organization. Metrics are needed to narrow areas that require attention for continuous improvement (Kaizen) initiatives, and to quantify the organization’s ongoing improvement achievements. We cannot improve what we cannot measure.
Six Sigma practitioners use the DMAIC process to systematically reduce variability in a manufacturing process. Lean practitioners also refer to the Toyota problem solving methodology and kaizen workshops. All of these different methodologies can come together in a Corrective Action system to track all continuous improvement efforts. An Enterprise Quality Management System (EQMS) and Corrective and Preventive Action (CAPA) system are essential to documenting and tracking the entire problem-solving process ensuring a consistent review process and a closed-loop methodology that verifies effectiveness of the corrective action or reopens the problem for further analysis. The corrective action system can be used to also track and resolve productivity problems that are not related to quality issues.
Lean Manufacturing and Six Sigma practitioners use slightly different terminology and methodologies for continuous improvement processes, but they are really more similar than different. The different terminology and methods are discussed in the article: “Comparing Lean Manufacturing And Six-Sigma Continuous Improvement Efforts”.
The inspection and parts genealogy data recorded during manufacturing is not only used for performance metrics and root-cause analysis. In regulated industries, historical data is required to allow process certification and audits. Regulatory compliance and audit considerations are becoming more common in many industries. Regulatory guidelines from agencies like ISO, FDA, FAA, DoD, or ASME are all aimed at encouraging process control and quality assurance throughout the entire manufacturing process in order to achieve consistent quality results at the end. This general goal of the guidelines should be embraced as a goal to eliminate waste of poor quality due to deficient quality management processes.
Manufacturers have tackled regulatory requirements in the past with tons of paperwork, labor intensive validation processes, and a variety of disconnected systems and spreadsheets. Many of these old processes require double validation because manual procedures are prone to error. However, modern manufacturing and quality management software solutions can streamline and automate processes making it possible to improve productivity while enforcing compliance. The article “Reducing Cost Of Quality With Integrated MOM And EQMS” discusses more about using manufacturing operations management software to reduce cost of quality.
In today’s highly outsourced manufacturing practices, it is critical that the requirements for quality management reach out to partners and suppliers. For future competitiveness, it will not be enough to focus on schedule and cost reduction, it is necessary to increase visual acuity on the quality side. For more ideas on how to connect the supply chain, see the article: “Vision 2020 For Quality In The Extended Value Chain”.
I agree with you on the role that Quality management plays in the Lean Manufacturing. Quality has become the necessary tool for almost everything. The growing concern is how to ensure the companies embrace new ways of doing things. Thanks for the insight.
Posted by: Doreen Nanyama | July 02, 2017 at 11:50 PM