We’ve seen them referred to as “The Old Seven” or “The First Seven.”
They’re the seven basic quality engineer tools for process improvement. In this blog entry, we’ll explore how each one of these tools works.
1. The Cause And Effect Diagram
This is also called the “Ishikawa Diagram” (after the Japanese organizational theorist Kaoru Ishikawa) or the “fishbone diagram” (because of how it appears on the page).
And as the name we’ve used suggests, it’s used to determine what has caused a problem.
To make a diagram, begin by writing out the problem on a white board or a chart and draw a box around the problem, with a horizontal arrow running to the box. (Think of this as the head, backbone and tail of the “fish.”)
Then name some of the possible causes of the problem (“Materials,” “Equipment” “Manpower,” etc.). With each one, draw other arrows leading off from the main arrow.
Then, go deeper, discussing possible causes within each main category, and drawing more lines. Eventually, you’ll have created a detailed diagram that looks like a fishbone, and given your team a lot to discuss and digest.
2. The check Sheet
This form – also known as a “defect concentration diagram” – lets you collect and analyze data on the frequency of which a problem or defect occurs.
The American Society for Quality uses this example: A company wanted to track data on how many telephone interruptions its office received during a work week. It used a check sheet that marked off the number of calls that came in each day, and the type of call: wrong numbers (20) requests for information (10) and calls from the boss (19).
3. Control Chart
This is a graph used to explore how a process evolves over time. You plot data in time order, with a central line measuring the average, an upper line for the upper control limit and a lower line for the lower control limit. These lines are determined using historic data.
By comparing current data to the historic data, you can make conclusions about whether the process variation is consistent (in other words, in control) or unpredictable (and therefore, not in control).
You can use these charts to determine if your quality improvement project should try to prevent a particular problem or make larger changes to the process.
A histogram is a type of bar chart that graphs how often continuous data occurs, and helps you analyze that data. They are useful to help you see and understand variations in data.
You would use a histogram when dealing with numerical data, when you want to see the shape of the data’s distribution. It can also help you analyze whether a process can meet a customer’s needs, and help you study what the output from a supplier’s process looks like.
5. Pareto Chart
The Pareto chart (or Pareto diagram) is another type of bar graph. The bars represent time or money, and are arranged with the longest bars to the left, the shortest to the right, in order to depict which is the most significant.
For example, you could set up a Pareto chart outlining what your company spent on different types of supplies. If, for example, the chart showed you spending the most money on paper, you could begin to look at ways to go paperless at work.
6. Scatter Diagram
A scatter diagram graphs numerical data in pairs, with one variable on each axis, looking for a relationship between them. If there is a correlation, the points will fall along a curve or a line. The closer the correlation, the tighter the points will be on the line.
After you’ve looked at causes and effects on the fishbone diagram, the scatter diagram can help you conclude whether specific causes and effects are connected.
7. Flow Charts
A flow chart is a visual representation of the sequence of steps involved in a process, event or service. It provides a common point of reference of complex processes to spark discussion and analysis.
Flow charts can also outline an existing process and point to potential ways to improve it. There are a number of types of flowcharts.
For example, a top down flow chart stresses the main steps in a process while just briefly touching on details. A workflow diagram allows you to show the movement of tasks, information, material or action from one point to another: Production to distribution to sales.
Part of your quality control work is ensuring you have tools that function well. Maxpro can help you achieve that goal, through its expert calibration services and by renting and selling superior torque tools. Contact us today to learn more about how we can assist your next project.