Eight disciplines problem solving
Eight Disciplines Problem Solving
Eight disciplines (8Ds) problem
solving is a method developed at Ford Motor Company used to approach and to resolve problems,
typically employed by
engineers or other professionals. Focused on product and process improvement,
its purpose is to identify, correct, and eliminate recurring problems.
It
establishes a permanent corrective action based on statistical analysis of the
problem and on the origin of the problem by, determining the root causes.
Although
it originally comprised eight stages, or 'disciplines', it was later augmented
by an initial planning stage.
8D follows the logic of the PDCA cycle. The
disciplines are:
D0: Preparation
and Emergency Response Actions: Plan for solving the problem and determine
the prerequisites. Provide emergency response actions.
D1: Use a
Team: Establish a team of people with product/process knowledge. Teammates provide
new perspectives and different ideas when it comes to problem solving.
D2: Describe
the Problem: Specify the problem by identifying in quantifiable terms the
who, what, where, when, why, how, and how many (5W2H) for the problem.
D3: Develop
Interim Containment Plan: Define and implement containment actions to
isolate the problem from any customer.
D4: Determine
and Verify Root Causes and Escape Points: Identify all applicable causes
that could explain why the problem has occurred. Also identify why the problem
was not noticed at the time it occurred. All causes shall be verified or
proved.
One can use five
whys or Ishikawa diagrams to map
causes against the effect or problem identified.
D5: Verify
Permanent Corrections (PCs) for Problem will resolve problem for the customer:
Using pre-production programs, quantitatively confirm that the selected
correction will resolve the problem. (Verify that the correction will actually
solve the problem).
D6: Define
and Implement Corrective Actions: Define and implement the best corrective
actions. Also, validate corrective actions with empirical evidence of
improvement.
D7: Prevent
Recurrence / System Problems: Modify the management systems, operation
systems, practices, and procedures to prevent recurrence of this and similar
problems.
D8: Congratulate
the Main Contributors to your Team: Recognize the collective efforts of the
team. The team needs to be formally thanked by the organization.
8Ds has become a standard in the automotive assembly,
and other industries that require a thorough structured problem-solving process
using a team approach.
Ford Motor Company's
team-oriented problem solving
The executives of the Power-train Organization (transmissions, chassis, engines) wanted a
methodology where teams (design engineering, manufacturing engineering, and
production) could work on recurring chronic problems.
In 1986, the assignment
was given to develop a manual and a subsequent course that would achieve a new
approach to solving identified engineering design and manufacturing problems.
The manual for this methodology was documented and defined in Team Oriented
Problem Solving (TOPS), first published in 1987.
The manual and subsequent
course material were piloted at Ford World
Headquarters in Dearborn, Michigan. Ford refers to their current variant as G8D (Global 8D). The Ford 8Ds
manual is extensive and covers chapter by chapter how to go about addressing,
quantifying, and resolving engineering issues. It begins with a
cross-functional team and concludes with a successful demonstrated resolution
of the problem. Containment actions may or may not be needed based on where the
problem occurred in the life cycle of the product.
Usage
Many disciplines are typically involved in the "8Ds"
methodology. The tools used can be found in textbooks and reference materials
used by quality assurance
professionals. For example, an "Is/Is Not" worksheet is a common tool
employed at D2, and Ishikawa, or "fishbone," diagrams and "5-why
analysis" are common tools employed at step D4. In the late 1990s, Ford
developed a revised version of the 8D process that they call "Global
8D" (G8D), which is the current global standard for Ford and many other
companies in the automotive supply chain. The major revisions to the process
are as follows:
- Addition of a D0 (D-Zero) step as a gateway to the process. At D0, the team documents the symptoms that initiated the effort along with any emergency response actions (ERAs) that were taken before formal initiation of the G8D. D0 also incorporates standard assessing questions meant to determine whether a full G8D is required. The assessing questions are meant to ensure that in a world of limited problem-solving resources, the efforts required for a full team-based problem-solving effort are limited to those problems that warrant these resources.
- Addition of the notion of escape points to D4 through D6. An 'escape point' is the earliest control point in the control system following the root cause of a problem that should have detected that problem but failed to do so. The idea here is to consider not only the root cause, but also what went wrong with the control system in allowing this problem to escape.[1] Global 8D requires the team to identify and verify an escape point at D4. Then, through D5 and D6, the process requires the team to choose, verify, implement, and validate permanent corrective actions to address the escape point.
Recently, the 8D process has been employed significantly outside the
auto industry. As part of lean initiatives and continuous-improvement processes
it is employed extensively in the food manufacturing, health care, and
high-tech manufacturing industries.
Benefits
The benefits of the 8D methodology include effective approaches to
finding a root cause, developing
proper actions to eliminate root causes, and implementing the permanent
corrective action. The system also helps to explore the control systems that
allowed the problem to escape. The Escape Point is studied for the purpose of
improving the ability of the Control System to detect the failure or cause when
and if it should occur again. Finally the Prevention Loop explores the systems
that permitted the condition that allowed the Failure and Cause Mechanism to
exist in the first place.
Prerequisites
Requires training in the 8D problem-solving process as
well as appropriate data collection and analysis tools such as Pareto charts, fishbone
diagrams, and process maps.
Problem solving tools
The following tools can be used within 8D:
- Ishikawa diagrams also known as cause-and-effect or fishbone diagrams
- Pareto charts or Pareto diagrams
- 5 Whys
- 5W and 2H (who, what, where, when, why, how, how many or how much)
- Statistical process control
- Scatter plots
- Design of experiments
- Check sheet
- Histograms
- FMEA
- Flowcharts or process maps
Background of common
corrective actions to dispose of nonconforming items
The 8D methodology was first described in a Ford manual in 1987. The
manual describes the eight-step methodology to address chronic product and
process problems. The 8Ds included several concepts of effective problem
solving, including taking corrective actions and containing nonconforming
items. These two steps have been very common in most manufacturing facilities,
including government and military installations. In 1974, the U.S. Department
of Defense (DOD) released “MIL-STD 1520 Corrective Action and Disposition
System for Nonconforming Material”. This 13 page standard defines establishing
some corrective actions and then taking containment actions on nonconforming
material or items. It is focused on inspection for defects and disposing of
them. The basic idea of corrective actions and containment of defectives was
officially abolished in 1995, but these concepts were also common to Ford Motor
Company, a major supplier to the government in World War II. Corrective actions
and containment of poor quality parts were part of the manual and course for the
automotive industry and are well known to many companies. Ford's 60 page manual
covers details associated with each step in their 8D problem solving manual and
the actions to take to deal with identified problems.
Military usage
The exact history of the 8D method remains disputed as many publications
and websites state that it originates from the US military. Indeed,
MIL-STD-1520C outlines a
set of requirements for their contractors on how they should organize
themselves with respect to non-conforming materials. Developed in 1974 and
cancelled in February 1995 as part of the Perry memo, you can
compare it best to the ISO 9001 standard that currently exists as it expresses
the same philosophy. The aforementioned military standard does outline some
aspects that are in the 8D method, however, it does not provide the same
structure that the 8D methodology offers. Taking into account the fact that the
Ford Motor Company played an instrumental role in producing army vehicles
during the Second World War and in the decades after, it could very well be the
case that the MIL-STD-1520C stood as a model for today’s 8D method
Relationship between 8D and
FMEA
FMEA (failure mode and effect analysis) is a tool generally used in the
planning of product or process design. The relationships between 8D and FMEA
are outlined below:
- The problem statements and descriptions are sometimes linked between both documents. An 8D can utilize pre-brainstormed information from a FMEA to assist in looking for potential problems.
- Possible causes in a FMEA can immediately be used to jump start 8D Fishbone or Ishikawa diagrams. Brainstorming information that is already known is not a good use of time or resources.
- Data and brainstorming collected during an 8D can be placed into a FMEA for future planning of new product or process quality. This allows a FMEA to consider actual failures, occurring as failure modes and causes, becoming more effective and complete.
- The design or process controls in a FMEA can be used in verifying the root cause and Permanent Corrective Action in an 8D.
The FMEA and 8D should reconcile each failure and cause by cross
documenting failure modes, problem statements and possible causes. Each FMEA
can be used as a database of possible causes of failure as an 8D is developed.
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