Posts in category Six Sigma

When using a scatter diagram there are two types of variables – a dependent variable and an independent variable. The independent variable is usually a plotted along the horizontal axis. The dependent variable is usually plotted along the vertical axis. If no dependent variable exists, either type of variable can be plotted on either axis. If the clustering of intersecting dots in the paired comparisons shows a pattern that extends from lower-left to upper-right, the scatter diagram shows evidence of a positive correlation. If the pattern of dots tends to go from the upper-left to the bottom-right, there is evidence of a negative correlation.

The project scope defines the boundaries of the project. The project scope keeps the team on purpose, in alignment, contained, focused, and motivated.

The scope might include:

The start time and stop time,
The duration,
The process boundaries (what is within scope, and what is out of scope),
The sub processes involved,
The product lines,
The locations (the divisions, the states, the territories, the countries, etc.)

The expression “Learning to see” comes from an ever developing ability to see waste where it was not perceived before. Many have sought to develop this ability by ‘trips to Japan’ to visit Toyota to see the difference between their operation and one that has been under continuous improvement for thirty years under the TPS. The following “seven wastes” identify resources which are commonly wasted. They were identified by Toyota’s Chief Engineer, Taiichi Ohno as part of the Toyota Production System.

Applicable to run charts and control charts, a shift in its most basic form is seven points in a row either above or below the centerline. A trend is seven points in a row in an upward direction or seven points in a row in a downward direction. With a trend, it doesn’t matter if the centerline is crossed.

A quick changeover (sometimes called a Single Minute Exchange of Die or SMED) is a tool used by lean production to reduce the amount of time it takes to change from running one part or product to running a different one. It is also referred to as setup reduction.

Quick changeovers have the potential to reduce costs, improve cycle time, and increase process flexibility. The reason why they call it Single Minute Exchange of Die is due to the one time goal to try to get the changeover time, measured in hours, down to a time measured in single digits (e.g., 9 minutes, 8 minutes, etc.) ever since that was accomplished, the whole idea of SMED spread.

For the ease of understanding, this author is using the word ‘piece’ to mean (in the generic sense) the making of a tangible product. It could be an ice cream cone, a widget, or an automobile. One of the tenets of lean is single piece flow. Instead of building up a stack of inventory between the steps in the process, the idea with single piece flow (also known as one piece flow), is to build at the pulse rate of customer demand. This pulse rate of customer demand, known as takt time, ebbs and flows over time. With single piece flow, the idea is to make a piece only when the customer asks for one.

The mapping process starts with identifying the customers’ needs and requirements. The team then determines the outputs of the process that have an effect on those requirements. The team lists 5 to 7 high-level steps of the process. They begin to identify the inputs to the process and the suppliers who provide for those inputs. SIPOC is an effective way of seeing the whole value-add process on one graphic. It shows the relationships between inputs and outputs.

There may be thousands of factors that directly affect or interact with each other to affect the outcome of some desired result(s) of a process. The 6M’s started with Dr. Ishikawa as the 4M’s (Machine, Material, Method, Measurement) and over time it evolved to including the human element and noise factors affected by the forces of nature (e.g., humidity, vibration, temperature, etc.) The team uses these 6M’s as memory joggers to focus on when they are identifying as many of the factors that might influence the process as possible. Typically, they will use a Fishbone Diagram along with brainstorming to gather these ideas. After the team has exhausted the brainstorming session, the team will then boil down the many factors to the vital few factors from which they will place their monitoring, controlling, and improvement methodologies.

Six sigma is a process improvement methodology which at its core focuses on making virtually any process more effective and efficient.

A spaghetti diagram (also known as a workflow analysis diagram) is used to present the workflow or movement of people, materials, and information through a process.
A spaghetti diagram is particularly useful in identifying inefficiency and waste in a process.