Six Sigma quality control methods are currently used the world over. The system’s principles help companies to decrease variables that cause defects, thus increasing product quality. Six Sigma helps to better customer service, increase company image, and decrease on capital invested in production.
Six Sigma follows two separate methodologies to accomplish its goals. They are DMAIC and DMADV. DMAIC is used for Six Sigma projects that are designed to improve upon an already existing business process. DMADV, on the other hand, is used for Six Sigma projects that seek to create new processes or products. Each of the methods were inspired by an earlier plan known as PDCA (Plan-Do-Check-Act) which was also known as the Deming Wheel.
While Six Sigma can help a company improve upon quality, it helps to first understand these two methodologies and how they are beneficial.
What Is DMAIC?
Define: Means to define high-level and priority project goals and the process needed to achieve them. If there is a problem in the process, Six Sigma supervisors must define the problem clearly in order to fix it. To do this, there are several steps the Define stage uses:
- Identify the problems in the process that must be solved in order to achieve optimal workflow and to meet customer satisfaction.
- Identify the customer requirements.
- Identify the desired quality of a process’ output, identify the defects that do not meet those standards, and draw up a problem statement.
- State the goal of the project that will fix the problem and give a time frame for the completion of the project.
- Identify the vital aspects of the process that are needed because these must be measured, analyzed, improved and controlled.
- Design a project charter that includes such things as problem definition and goal as well as plans for the next stages in the DMAIC methodology.
Measure: Key aspects and characteristics of a process should be measured and data collected. This includes assembling the data into a plan, executing the plan, and making sure that the data was collected properly. To do this, Six Sigma members must:
- Select Critical-to-Quality characteristics. These is the process output which is vital to customer satisfaction.
- The outputs should be well defined by paying attention to customer requirements and the goal of the project itself.
- Identify and define the process or problem that produces defects.
- Calculate the financial means of eliminating the problem defects and if it will increase company profits or save money.
- To make sure that all defects are measured accordingly, Six Sigma members should use Measurment System Analysis.
After all the defects in a process have been measured, the process may be used as a measurement to compare against the new improved process.
Analyze: After everything has been measured, the data that is collected should be analyzed to determine the cause-and-effect relationship of the process in question. It is important that all variables are taken into consideration. The Analysis stage is often done by a Six Sigma Black Belt. By using the collected data, the Balck Belt will come up with a hypothesis on the cause of the problem in the process. By using statistical methods, the hypothesis will be tested.
Improve: After the data has been analyzed, a solution should be reached to improve the process. This stage is also completed by a Black Belt. The Black Belt’s responsibilities will be:
- Confirm the inputs that caused the variables which resulted in defects.
- Identify each input to make sure that it falls within the acceptable range of quality.
- Determine if the process needs adjusting.
- Decide if any additional or special measures are required to improve the process.
- Once the changes have been decided upon, put them into effect.
- Install a new measurement system for the new process.
- Monitor the system to make sure the changes are having the desired effect.
Control: The process needs to be controlled to ensure that all variables that lead to defects are corrected. The process should also be monitored continuously to watch out for recurring defects. Any process can be affected by a number of factors, no matter how small. By continually monitoring the process, operators can watch for variables that might pop up and correct them before they can cause further defects.
Six Sigma DMADV Method
Define: This stage is supposed to set the project goals that are needed to meet customer demand, satisfaction, and the overall strategy of the company.
Measure: This is used to identify the aspects that are important to Critical-to-Quality, process capabilities, customer satisfaction, and risks of the project in question.
Analyze: Data must be analyzed to develop alternative designs as well as evaluate certain design capabilities and select the most appropriate design. By analyzing the alternative processes, you can better achieve customer satisfaction.
Design: In this stage Six Sigma team members will optimize a design to get the most out of it. This involves design modifications and verification. The goal is to make the best possible to meet customer needs.
Verify: This stage makes sure the design works to perfection by setting up trial runs and finally implementing it into full production. Six Sigma team members monitor the new design before handing it back to the regular process operators.
In order for DMADV to work, a company must understand customer needs and requirements and to prioritize them. This translates into understanding who your customers are and listening to them. Most companies do not fully understand what their customers really need so are unable to provide it for them. This is where DMADV comes in. If the input is not reliable, the output will not meet customer satisfaction.