Quality is no longer a factor of merely satisfying customers but is also a factor of doing so consistently to build an experience worth their loyalty. However, when variation creeps in, the consistency in quality is lost. Variation does not only cost a business unnecessary production costs but will also eventually cost it, valuable customers, if nothing is done to minimize the risk of producing defective units. To deliver customer value, a business needs to
- Understand customer needs
- Design products/services that meet these needs
- Establish processes for producing the products and services
- Manage the processes to deliver to their expected capacity
In establishing processes, organizations have adopted the six sigma methodology to determine the mix of tools, technologies, and systems that will enable them to optimize the capacity of their processes. The aim of optimizing process capacity is to minimize process variation as much as possible to reduce defects and consistently maintain high-quality products. As such, organizations are always on the lookout for experts with Lean Six Sigma Black Belt Certification who are committed to employing DMAIC methodology to production processes to achieve continuous quality improvement.
Six Sigma and quality improvement
The Six Sigma concept puts together tools, techniques, and philosophies used to improve the capacity of business processes and optimize performance by minimizing process variation to reduce defects and errors while increasing profits. The goal of Six Sigma is to improve product quality, boost employee morale, and increase customer satisfaction.
To minimize process variation, Six Sigma employs the DMAIC methodology. DMAIC is an acronym for Define, Measure, Analyze, Improve, and Control. These represent the phases that business processes are taken through in an effort to improve them and optimize their capabilities.
Where does statistical process control (SPC) come in?
The very final phase of Six Sigma DMAIC is the control phase. The main objective of the control phase is to ensure that the solutions to process improvement are not only implemented, but they are also measured, documented, and most importantly, maintained. A standard procedure for monitoring the process is established to make it possible to spot issues (variations) if the process is not performing as expected and react to these issues accordingly.
The metrics used in defining the performance of the process would then be established as critical to quality improvement and this is where statistical process control (SPC) comes in.
What is Statistical Process Control (SPC)?
SPC is an industry-recognized methodology used during the final control phase of the Six Sigma DMAIC cycle to monitor production processes in real-time to ensure that they are performing as expected. In other words, SPC is a subset of Six Sigma; the broader process quality improvement methodology.
By continuously monitoring processes, SPC tools enable businesses to spot and address variations in processes in time through statistical analysis and to maintain process performance at the optimum. These same tools have been used successfully to monitor the quality of products and services that an organization offers its clients.
The main tool used in SPC to monitor process control is the control chart. The control chart is a graphical representation of both the input and output of a process over a period of time. It can be applied to any process, product, or service that meets the specifications established for process control and whose output can be measured. The output measurement is plotted on the graph over time is measured against specified control limits and variations established after which the causes of the variation are investigated.
Apart from control charts, the SPC toolset consists of the following tools:
- Pareto Charts
- Ishikawa Cause-and-Effect or Fishbone Diagrams
- Cross-sectional charts
- Run Charts
- The Mean Chart
- The Range Chart
- G charts
- Process Capability Analysis
- Taguchi Loss Function
Role of SPC in quality improvement
The overall goal of employing SPC in quality improvement is to establish and address process variations before they affect the quality of the process output (products and services). In essence, SPC tools should yield the average quality capacity of a process, basic variability of the quality variable, and the consistency of the performance of the process when applied. This is achieved by monitoring processes in real-time to ensure that they are operating in their full potential.
Other roles of statistical process control in quality improvement include:
1. Offers an in-depth understanding of how variables interact
SPC tools are used to analyze processes, products, and services using predetermined specifications. The desired output characteristics are weighed against predetermined specifications and a relationship is then established between the variability in the product characteristics and the specification limits put in place.
2. Evaluate the overall performance of processes
SPC does not only analyze process performance but also controls processes, makes a distinction between natural and assigned variables, and proactively point out potential special causes and provide insight on how to address them. It does establish variability to determine whether a process in working in control. Note that some variability between the optimal and actual process performance is inevitable.
3. Gives insight into areas and processes that need attention
While the DMAIC control process takes care of arising unusual quality issues in processes or products, the previous improvement process identifies persistent process issues. SPC tools make it possible to identify areas, within the process, that need attention, the improvement initiative to accord the process as well as estimates the corresponding return on investment. Finally, SPC tools will evaluate how much improvement the process records after an action has been taken.
4. Guides in the decision of the appropriate action to be taken to improve processes
Using SPC tools, the actual performance of a process/product is checked against predetermined specifications. If a product meets the specifications, either no further action is required or some action is required to further reduce variability. However, if the opposite is the case, the action is required. The action could mean finding approaches to reduce variability, revisiting the specifications, reworking the product e.t.c A control chart would give insight into the most appropriate actionappropriate action to be taken.
5. Used to predict the effect of a new strategy in a process
An in-depth analysis of process performance after the integration of a new strategy allows the prediction of its potential effect on the process or product. This eliminates the need for separate off-line testing which is often costly and time-consuming.
6. Used to detect process control issues early.
SPC is a prevention-based quality control tool. Through real-time monitoring, potential process issues can be detected and resolved well before they affect the quality of the outcome which may turn out to be scrap.
7. Minimizing waste, defects, and scrap
SPC is a waste reduction technique. Identifying the cause of variability early reduces waste, scrap, and instances of rework. This tools will also pick out the inferior quality raw material and prevent them from being used to produce finished products. This guarantees quality processes or finished products reduces order cancellations and costs associated with reworks.
8. Reduce process cost
Given the aggressive competition and increased cost of raw materials, businesses are faced with the challenge of finding other ways of maximizing profit. Reducing process costs and improving quality are two factors that fall directly under their control and which affect the profitability of the business.
9. Reduces the time required to produce a product/service.
With minimal process variation, SPC makes it possible to produce high-quality finished products that do not require scrapping or reworking.
All organizations have processes that affect product and/or service outcomes directly. It is critical to identify, monitor, control, and improve such processes. This way, continuous efforts will be made towards quality improvement and unnecessary waste eliminated. Statistical process control aims at taking initiatives in improving processes to produce outcomes that meet specifications. At the core or SPC is continuous improvement of processes, products, or services. The effect is an improvement in quality, productivity, and cost reduction. Overall, organizations that employ SPC achieve customer loyalty and increased profitability.