Adv. 1. just in time - at the last possible moment;
"she was saved in the nick of time"
Synonyms: in the nick of time
See also Just-in-time for the compiler system in computing
Just in Time, or JIT is a set of techniques to improve the return
on investment of a business by reducing in-process inventory, and
its associated costs. The process is driven by a series of signals,
or Kanban that tell production processes to make the next part.
Kanban are usually simple visual signals such as the presence or
absence of a part on a shelf.
JIT causes dramatic improvements in a manufacturing organization's
return on investment, quality, and efficiency.
HistoryThe technique was first adopted and publicised by Toyota
Motor Corporation of Japan as part of its Toyota Production System
Japanese corporations cannot afford large amounts of land to warehouse
finished products and parts. Before the 1950s this was thought to
be a disadvantage because it reduced the economic lot size. An economic
lot size is the number of identical products that should be produced,
given the cost of changing the production process over to another
product. The undesirable result would be a poor return on investment
for a factory.
The chief engineer at Toyota in the 1950s examined accounting assumptions,
and realized that another method was possible. The factory could
be made more flexible, reducing the overhead costs of retooling,
and therefore reducing the economic lot size to the available warehouse
Over a period of several years, Toyota engineers redesigned car
models for commonality of tooling for such production processes
as paint-spraying and welding. Toyota was one of the first to apply
flexible robotic systems for these tasks. Some of the changes were
as simple as standardizing the hole sizes used to hang parts on
hooks. The number and types of fasteners were reduced in order to
standardize assembly steps and tools. In some cases identical subassemblies
could be used in several models.
Toyota engineers then determined that the remaining critical retooling
operation was the time to change the stamping dies used for body
parts. Traditionally, these were adjusted by hand, with crowbars
and wrenches. It sometimes took as long as several days to install
a large (multiton) die set and achieve acceptable quality. Further,
these were usually installed one at a time by a team of experts,
so that the line would be down for several weeks.
Toyota implemented a program called "The Single Minute Exchange
of Die," SMED. With very simple fixtures, measurements were
substituted for adjustments. Almost immediately, die change times
fell to about a half hour. At the same time, quality of the stampings
became controlled by a written recipe, reducing the skill required
for the change. Analysis showed that the remaining time was used
to search for hand tools, and move dies. Procedural changes (moving
the new die in place with the line in operation) and dedicated tool-racks
reduced die change times to as little as 40 seconds. Dies were changed
in a ripple through the factory, as a new product began flowing.
After SMED, economic lot sizes fell to as little as one vehicle
in some Toyota plants.
Carrying the process into parts-storage made it possible to store
as little as one part in each assembly station. When a part disappeared,
that was used as a sign to produce or order a new part.
EffectsSome surprising things occurred. A huge amount of cash appeared,
apparently from nowhere, as in-process inventory was built out and
sold. This by itself generated tremendous enthusiasm in upper management.
Another surprising effect was that the response time of the factory
fell to about a day. This improved customer satisfaction by providing
vehicles usually within a day or two of the minimum economic shipping
Also, many vehicles began to be built to order, completely eliminating
any risk that they would not be sold. This dramatically improved
the company's return on equity by eliminating a major source of
Since assemblers no longer had a choice of which part to use, every
part had to fit perfectly. The result was a severe quality assurance
crisis, and a dramatic improvement in product quality. Eventually
Toyota redesigned every part of its vehicles to eliminate or widen
tolerances, while simultaneously implementing careful statistical
controls. (See Total Quality Management). Toyota had to test and
train suppliers of parts in order to assure quality and delivery.
In some cases, they eliminated multiple suppliers.
When a process problem or bad parts surfaced on the production
line, the entire production line had to be slowed, or even stopped.
No inventory meant that a line could not operate from in-process
inventory while a production problem was fixed. Many people in Toyota
confidently predicted that the initiative would be abandoned for
this reason. In the first week, line stops occurred almost hourly.
However, by the end of a month, the rate had fallen to a few line
stops each day. In six months, line stops had so little economic
effect that Toyota had an overhead pull-line, similar to a bus bell-pull,
that permitted any worker on the production line to order a line
stop for a process or quality problem. Even with this, line stops
fell to a few per week.
The result was a factory that became the envy of the industrialized
world, and which has since been widely emulated.
The Just in Time philosophy was
also applied other segments of the supply chain in several types
of industries. In the commercial sector it meant eliminating one
or all of the warehouses in the link between a factory and a retail
Statistical process control
Total Quality Management
Vendor Managed Inventory