Lean Six Sigma has developed its own vocabulary
to express its underlying concepts and operational processes.
Here are definitions of the some of the more commonly used
terms. Because of Lean’s origins in Japan, Japanese equivalent
terms are shown in parentheses in some cases.
The “5 Whys.” The “5 Whys” typically
refers to the practice of asking 5 times why a failure has
occurred in order to get to the root cause of any problem.
Of course, a problem can have more than one cause. Generally,
root cause analysis is carried out by a team of people who
are related to the problem. No special technique is required.
The “5S’s.” Five terms beginning
with “S” are used to create a workplace suited
for visual control and Lean production.
- Sort (Seiri). Eliminate everything that is not required for the current process and keep only the bare essentials.
- Straighten (Seiton). Arrange all items so that they are easily visible and accessible.
- Shine (Seiso). Clean everything, and find ways to keep everything clean. Make cleaning a part of everyday work habits.
- Standardize (Seiketsu). Create rules by which the
first three S’s are maintained.
- Sustain (Shitsuke). Keep 5S activities from unraveling.
Balanced scorecard. This is a strategic management system
used to drive performance and accountability. It balances traditional performance
measures with more forward-looking
indicators, such as finances, integration and operational excellence, employees,
Benchmarking. This is an improvement process that an
organization uses to compare its performance against best-in-class companies.
It then uses the information
gathered to improve its own performance. Subjects that can be benchmarked include
strategies, products, programs, services, operations, processes, and procedures.
Black Belt. Six
Sigma team leaders responsible for implementing process
improvement projects to increase customer satisfaction
and business productivity are
known as “Black Belts.” They are knowledgeable and skilled in the
use of Six Sigma methodology and tools, typically have completed 4 weeks of
training, and have demonstrated a mastery of the subject matter through the
of projects and an examination.
Cell. A cell is a group of people, machines, materials,
and methods arranged so that processing steps are located adjacent to each other
and in sequential
order. This allows parts to be processed one at a time or, in some cases, in
a constant small batch that is maintained through the process sequence. The purpose
of a cell is to achieve and maintain an efficient, continuous flow of work.
Continuous flow. Each process, whether in an office
or plant setting, makes or completes only the one piece that the next process
needs; the batch size is one.
Single-piece flow, or one-piece flow, is the opposite of a batch-and-queue process.
Cycle time. This is the time a person needs to complete
an assigned task or activity
before starting again.
acronym stands for “define, measure, analyze, improve, and
control. It is the heart of the Six Sigma process and refers to a data-driven
quality strategy for improving processes. It is an integral part of any company’s
Six Sigma quality initiatives.
Green Belt. A
Green Belt is an employee who has been trained on the
Six Sigma improvement methodology and will lead a team.
of knowledge and skills
associated with Six Sigma is less than that of a Black Belt or Master Black
Belt. Extensive product knowledge is a must in a green
Belt’s task of process
Heijunka. This Japanese term refers to the act of leveling
the variety or volume of items produced by a specific process over a period of
time. This system is
used to avoid excessive batching of product types or volume fluctuations, especially
with a pacemaker process.
JIT. “JIT” stands for “just in time.” This
means producing or conveying only the items that are needed by the next process
when they are
needed and in the quantity needed. This process can even be used between facilities
Kaban. This is a signaling device that gives instructions
for production or conveyance
of items in a pull system.
Kaizen. “Kaizen” is the Japanese word
for improvement. However, it implies more than improvement in the basic production
a philosophy by which an organization and the individuals within it undertake
continual improvements in all aspects of organizational life, based on the
idea that a process is never perfect.
Lean. This is simply
a thought process, not a tool. The key thought processes
within Lean are identifying waste from the customer’s perspective and
then determining how to eliminate it.
Master Black Belt. These
are Six Sigma quality experts who are responsible for strategic implementations
within an organization. Their
include training and mentoring of Black Belts and Green Belts; helping to prioritize,
select, and charter high-impact projects; maintaining the integrity of Six
Sigma measurements, improvements, and “tollgates” (control points);
and developing, maintaining, and
revising Six Sigma training materials.
Material flow. The movement of a physical product through
the value stream.
One-piece flow. In its purest form, one-piece flow
means that items are processed and moved directly to the next station one piece
at a time. Each processing step
completes its specific work just before the next process needs the item; the
transfer batch is one.
Opportunity cost. This is the foregone value of an
alternative that is precluded by choosing another alternative. Other types of
costs may include variable, fixed,
direct, indirect, period, and product.
Overproduction. This is the process of producing more,
sooner, or faster than
is required by the next process or customer.
Procedure (Poka Yoke). This is a mistake-proof device
or procedure designed to prevent a defect from occurring throughout the system
Productivity. This is the ratio of measured outputs
over measured inputs, such
as the number of widgets produced per man-hour.
Six Sigma. The Six Sigma process is designed to eliminate
variances in a process in order to allow the best flow of work using the necessary
Standard work. This
term refers to a precise description of each work activity’s
cycle time, “takt time” (see below), sequence of specific tasks,
and the minimum inventory of parts needed on hand to conduct the activity.
Supermarket. This is a very visible, controlled inventory
of items that is used
to schedule production at an upstream process.
Takt time. This is the rate of demand from a customer.
Takt time equals the available
operating time or requirement.
Theory of constraints. This theory describes the methods
used to maximize operating income when an organization is faced with bottleneck
Value. This term refers to a product or service capability
that is provided to
a customer at the right time and at an appropriate price.
Value stream. This term encompasses all activities,
both value added and non-value added, that are required to bring a product, group,
or service from the point
of order to the hands of a customer and a design from concept to launch to production
Value stream mapping. This
is a pencil-and-paper tool used to—
- Follow a product or information (or both) activity path from beginning to end and draw a visual representation of every process—whether value added and
non-value added—in the material and information flows.
- Design a future-state map that has waste removed and creates more flow.
- Produce a detailed implementation plan for the future state of the organization.
Waste (Muda). Waste includes anything that does not add
value to a final product or service, such as an activity that the customer
would not want to pay for if it knew it was happening.
Waste types. Sources of waste can include overproduction, excess inventory,
defects, overprocessing, unneeded motion, wasted employee talents, waiting,
transport delays, and reprioritization actions.
WIP (Work in process). These are items—material or information—that
are between machines, processes, or activities waiting to be processed.