is a management philosophy aimed at eliminating manufacturing wastes by
producing only the right amount and combination of parts at the right
place at the right time. This is based on the fact that wastes result
from any activity that adds cost without adding value to the product,
such as transferring of inventories from one place to another or even
the mere act of storing them.
The goal of JIT, therefore, is to minimize the
presence of non-value-adding operations
and non-moving inventories
in the production line. This will result in shorter throughput times,
better on-time delivery performance, higher equipment utilization, lesser
space requirement, lower dpmís, lower costs, and greater profits.
JIT finds its origin in Japan, where it has been in practice since the
early 1970ís. It was developed and perfected by
Taiichi Ohno of
Toyota, who is now referred to as the father of JIT. Taiichi Ohno
developed this philosophy as a means of meeting customer demands with
minimum delays. Thus, in the olden days, JIT is used not to reduce
manufacturing wastage, but primarily to produce goods so that customer
orders are met exactly when they need the products.
JIT is also known as lean production
or stockless production,
since the key behind a successful implementation of JIT is the reduction
of inventory levels at the various stations of the production line to
the absolute minimum. This necessitates good coordination between
stations such that every station produces only the exact volume that the
next station needs. On the other hand, a station pulls in only the exact
volume that it needs from the preceding station.
The JIT system consists of defining the production flow and setting up
the production floor such that the flow of materials as they get
manufactured through the line is smooth and unimpeded, thereby reducing
material waiting time. This requires that the
capacities of the
various work stations that the materials pass through are very
evenly matched and
balanced, such that bottle necks in the production line are eliminated.
This set-up ensures that the materials will undergo manufacturing
without queueing or stoppage.
Another important aspect of
JIT is the use of a
'pull' system to move
inventories through the production line. Under such a system, the
requirements of the next station is what modulates the production of a
particular station. It is therefore necessary under JIT to define
a process by which the pulling of lots from one station to the next is
JIT is most applicable to operations or production flows that do not
change, i.e., those that are simply repeated over and over again. An
example of this would be an automobile assembly line, wherein every car
undergoes the same production process as the one before it.
JIT has likewise been practiced successfully by some semiconductor
companies. Still, there are some semiconductor companies that donít
practice JIT for the simple reason that their operations are too complex
for JIT application. On the other hand, thatís precisely the challenge
of JIT Ė creation of a production set-up that is
enough to allow JIT.
Guidelines for Successful JIT Implementation
the factory loadings uniform, linear, and stable. Fluctuations in
manufacturing loadings will result in bottlenecks.
Reduce, if not eliminate, conversion and set-up times.
lot sizes. This will smoothen out the flow of inventories from one
station to another, although this may necessitate more frequent
deliveries or transfers.
lead times by moving work stations closer together and streamlining the
production floor lay-out, applying cellular manufacturing concepts,
using technology to automate processes and improve coordination.
equipment downtimes through good preventive maintenance.
6) Cross-train personnel to achieve a very flexible work force.
stringent supplier quality assurance since an operation under JIT can
not afford to incur errors due to defects.
a control system to convey lots between workstations efficiently; the
use of a kanban system is an example of this
systems are often associated with JIT implementation. In fact, some
people have the misimpression that JIT requires the use of a kanban
system. Having a kanban system is not a strict requirement of JIT
implementation, but their use as a tool for practicing JIT has become
popular owing to its simplicity.
A kanban is a card attached
to the carrier or container of a lot used to match what needs to be
produced in a work station and what needs to be delivered to the next
station. As mentioned, a JIT system is basically a
which means that what needs to be produced in a particular station
depends on what the next station needs. Ultimately the production is
therefore modulated by end customer orders. Kanbans, which contain
information about the lots and quantities involved, are therefore used
to facilitate the execution of this 'pull' system. With this
'pull' system, no parts that can not be processed in succeeding stations
will be produced.
There are two types of
kanban assigned to every lot, namely, a
(P-kanban) and a
(C-kanban). The P-kanban denotes the need to produce more parts
while the C-kanban denotes the need to deliver more parts to the next
station. No parts can be produced unless authorized by a P-kanban. On
the other hand, a C-kanban triggers the 'pulling' or 'withdrawal' of
units from the preceding station. C-kanbans are also known as 'move' or
Just-In-Time (JIT); TPM; TQM; Kaizen; 6-Sigma; 5S Process
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