-
Buffer time, in project management, is the
extra time added into a time estimate to keep a
project
on track.
There are
two general types of buffer time.
?
?
Project buffer time
Task
buffer time
Project buffer time is the
time that is added to the end of the project (or
at various critical points
along the
way) that is managed by the project manager.
Task buffer time is specific to
individual tasks along the way. Sometimes this
form of buffer is
officially reported
to the project manager, but more often, it is
embedded in the task time. For
instance, an engineer may think that
designing a new fixture will take four days, but
reports five
to give a little bit of
buffer time to himself.
Project
managers (PMs) prefer to have all the buffer time
consolidated. They want aggressive
estimates from team members. Then the
PM can parcel out the buffer time wherever it is
needed.
This keeps the total project
time down.
Team members, on the other
hand, like to control their own buffer time so
they don‘t appear to
be late on
deliveries. The downside of this method is that
Parkinson’s Law
sneaks in
and results
in people using up the
buffer time, or allowing
scope
creep
to set i
n, when there
is a bit of ?extra‘
time.
Cyril Northcote Parkinson first
published this idea in
The
Economist
in 1955. In essence, the
concept says that work expands to fill
the time available.
So, why
does Parkinson‘s Law exist? It is simple
psychology
: people tend to
slow down when
they feel like they have
a lot of time, and speed up when they feel
pressure.
When a task has some extra
buffer time
in it, most
people will either take it easy along the way,
or try to add in
bells and
whistles
to make it
perfect
. When that is the
case, teams start trying to
spit and
polish every chart, and they try to squeeze
another half of a percent on top of a 17%
productivity
gain. The
problem is not that people are shooting for
quality
work. The problem is
that those incremental gains take a lot
of time
—
time that would be
better spent trying to solve
another
problem instead. Perfection is expensive.
The best way to counter
Par
kinson‘s Law is through the
continuous improvement
mantra
better, not perfect
.
Parkinson‘s Law is heavily influenced
by the
Pareto Principle
orthe
80/20 rule
. For example,
when you are given a task, you will
probably accomplish 80% of the work fairly quickly
and
easily. The last 20%, though,
always seems to take forever to complete.
The scope is the boundary of something
in business.
You may see
the term ‘scope’ applied an agreement or contract.
The
scope defines what is covered and
what is not.
In
Lean
, the scope is the
boundary of what a project will cover.
Scope can define
?
the time (a three week
study),
?
a
process (assembling a wiring harness, or Station
12),
?
or
physical location (the Midwest sales
region).
Scoping a project
well matches the available resources to the goals
of the team.
Teams often have a problem with adding
tasks and objectives along
the way.
This phenomenon is known as
scope
creep
, and should be
carefully managed. If the added tasks
are important, the team
champion will
need to add resources or remove other objectives
to
ensure project success.
Approach to continuous
improvement (reducing operating expenses and
inventory and increasing
throughput)
based on a five-step procedure: (1) identifying
constraints, (2) exploiting the binding
constraints, (3) subordinating
everything else to the decisions made in the
second step, (4)
increasing capacity of
the binding constraints, and (5) repeating the
process when new binding
constraints
are identified. It seeks to identify a company's
constraints or bottlenecks and exploit
them so that throughput is maximized
and inventories and operating costs are minimized.
3G
third-generation mobile technology that
usually includes services such as video telephony,
downloading information, e-mail, and
instant messaging.
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The
theory of constraints
(TOC)
adopts the common idiom
weakest
link
vulnerable because the weakest
person or part can always damage or break them or
at least
adversely affect the outcome.
The analytic approach with TOC comes
from the contention that any manageable system is
limited in achieving more of its goals
by a very small number of constraints, and that
there is
always at least one
constraint. Hence the TOC process seeks to
identify the constraint and
restructure
the rest of the organization around it, through
the use of
five focusing
steps
.
Contents
?
?
?
?
?
?
?
?
?
1
History
o
1.1Key assumption
o
1.2 The five
focusing steps
o
1.3Constraints
o
1.4
Buffers
o
1.5Plant types
2Applications
o
2.1Operations
o
2.2 Supply
chain / logistics
o
2.3 Finance and
accounting
o
2.4Project management
o
2.5Marketing
and sales
3 The TOC thinking
processes
4 Development and
practice
5Criticism
o
5.1 Claimed
suboptimality of drum-buffer-rope
o
5.2Unacknowledged debt
6 See also
7References
8Further reading
9External links
History
The
theory of constraints (TOC)
is an overall management philosophy introduced by
Eliyahu
M.
Goldratt
in his 1984 book titled
The Goal
, that is geared to
help organizations continually
achieve
their goals.
[1]
Goldratt
adopted the concept with his book
Critical Chain
, published
1997.
The concept was extended to TOC
with respectively titled publication in 1999.
An earlier propagator of the concept
was Wolfgang Mewes
[2]
in
Germany with publications on
power-
oriented management theory
(MachtorientierteFü
hrungstheorie, 1963)
and following with
his
Energo-Kybernetic System (EKS,
1971)
, later renamed
Engpass
konzentrierteStrategie
[3]
as
a
more advanced
theory of
bottlenecks
. The publications of
Wolfgang Mewes are marketed
through the
FAZ Verlag, publishing house of the German
newspaper
Frankfurter
AllgemeineZeitung
. However,
the paradigm
Theory of
constraints
was first used by Goldratt.
Key assumption
The
underlying premise of theory of constraints is
that organizations can be measured and
controlled by variations on three
measures: throughput, operational expense, and
inventory.
Throughput is the rate at
which the system generates money through sales.
Inventory is all the
money that the
system has invested in purchasing things which it
intends to sell. Operational
expense is
all the money the system spends in order to turn
inventory into
throughput.
[4]
The goal itself is to make money. All
other benefits are derived, in one way or another,
from that
single primary goal.
The five focusing steps
Theory of constraints is based on the
premise that the rate of goal achievement is
limited by at
least one constraining
process. Only by increasing flow through the
constraint can overall
throughput be
increased.
[1]
Assuming the goal of the organization
has been articulated (e.g.,
future
1.
Identify the constraint (the resource
or policy that prevents the organization from
obtaining more of the goal)
2.
Decide how to
exploit the constraint (get the most capacity out
of the constrained process)
3.
Subordinate
all other processes to above decision (align the
whole system or organization
to support
the decision made above)
4.
Elevate the constraint (make other
major changes needed to break the constraint)
5.
If, as a
result of these steps, the constraint has moved,
return to Step 1. Don't let
inertia
become
the constraint.
[5]
The five focusing steps aim to ensure
ongoing improvement efforts are centered around
the
organization's constraints. In the
TOC literature, this is referred to as the
process of ongoing
improvement
(POOGI).
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