Стратегия Jist-In-Time - на английски
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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 ( , Kanban?), that tell production processes when
to make the next part. Kanban are usually 'tickets' but can be simple
visual signals, such as the presence or absence of a part on a shelf.
When implemented correctly, JIT can lead to dramatic improvements in a
manufacturing organization's return on investment, quality, and
efficiency.
New stock is ordered when stock drops to the re-order level. This
saves warehouse space and costs. However, one drawback of the JIT
system is that the re-order level is determined by historical demand.
If demand rises above the historical average demand, the firm will
deplete inventory faster than usual and cause customer service issues.
To meet a 95% service rate a firm must carry about 3 standard
deviations of demand in safety stock. Forecasted shifts in demand
should be planned for around the Kanban until trends can be
established to reset the appropriate Kanban level. Others[1] have
suggested that recycling Kanban faster can also help flex the system
by as much as 10-30%. In recent years manufacturers have touted a
trailing 13 week average as a better predictor than most forecastors
could provide.
A related term is Kaizen which is an approach to productivity
improvement literally meaning "continuous improvement" of process.
History
The technique was first used by the Ford Motor Company as described
explicitly by Henry Ford's My Life and Work (1922): "We have found in
buying materials that it is not worthwhile to buy for other than
immediate needs. We buy only enough to fit into the plan of
production, taking into consideration the state of transportation at
the time. If transportation were perfect and an even flow of materials
could be assured, it would not be necessary to carry any stock
whatsoever. The carloads of raw materials would arrive on schedule and
in the planned order and amounts, and go from the railway cars into
production. That would save a great deal of money, for it would give a
very rapid turnover and thus decrease the amount of money tied up in
materials. With bad transportation one has to carry larger stocks."
This statement also describes the concept of "dock to factory floor"
in which incoming materials are not even stored or warehoused before
going into production. The concept needed an effective freight
management system (FMS); Ford's Today and Tomorrow (1926) describes
one.
The technique was subsequently adopted and publicised by Toyota Motor
Corporation of Japan as part of its Toyota Production System (TPS).
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 forced the production lot size below 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
was poor return on investment for a factory.
The chief engineer at Toyota in the 1950s, Taiichi Ohno ( , Ohno
Taiichi?), examined accounting assumptions and realized that another
method was possible. The factory could implement JIT which would
require it to be made more flexible and reduce the overhead costs of
retooling and thereby reduce the economic lot size to fit the
available warehouse space. JIT is now regarded by Ohno as one of the
two 'pillars' of the Toyota Production System.
Therefore 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
bottleneck in the retooling process was the time required to change
the stamping dies used for body parts. These were adjusted by hand,
using crowbars and wrenches. It sometimes took as long as several days
to install a large (multiton) die set and adjust it for acceptable
quality. Further, these were usually installed one at a time by a team
of experts, so that the line was down for several weeks.
So Toyota implemented a strategy called Single Minute Exchange of Die
(SMED), developed by Shigeo Shingo ( , Shing Shigeo?). With very
simple fixtures, measurements were substituted for adjustments. Almost
immediately, die change times fell to hours instead of days. At the
same time, quality of the stampings became controlled by a written
recipe, reducing the skill level required for the change. Further
analysis showed that a lot of the remaining time was used to search
for hand tools and move dies. Procedural changes (such as moving the
new die in place with the line in operation) and dedicated tool-racks
reduced the die-change times to as little as 40 seconds. Today dies
are changed in a ripple through the factory as a new product begins
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 signal (Kanban) to produce or order a replacement.
[edit] Philosophy
Just-in-time (JIT) inventory systems are not a simple method that a
company can adopt; it has a whole philosophy that the company must
follow in order to avoid its downsides. The ideas in this philosophy
come from many different disciplines including statistics, industrial
engineering, production management and behavioral science. In the JIT
inventory philosophy there are views with respect to how inventory is
looked upon, what it says about the management within the company, and
the main principle behind JIT.
Inventory is seen as incurring costs, or waste, instead of adding
value, contrary to traditional thinking. This does not mean to say
that JIT is unaware that removing inventory exposes manufacturing
issues. Under the philosophy, businesses are encouraged to eliminate
inventory that doesn't compensate for manufacturing issues, and to
constantly improve processes so that inventory can be removed.
Secondly, allowing any stock habituates the management to stock and it
can then be a bit like a narcotic. Management are then tempted to keep
stock there to hide problems within the production system. These
problems include backups at work centres, machine reliability, process
variability, lack of flexibility of employees and equipment, and
inadequate capacity among other things.
In short, the just-in-time inventory system is all about having "the
right material, at the right time, at the right place, and in the
exact amount" but its implications are broad for the implementors.
[edit] Criticisms
[edit] Shocks
JIT emphasises inventory as one of the seven wastes, and as such its
practice involves the philosophical aim of reducing input buffer
inventory to zero. Zero buffer inventory means that production is not
protected from exogenous (external) shocks. As a result, exogenous
shocks reducing the supply of input can easily slow or stop production
with significant negative consequences. For example as noted in Liker
(2003) Toyota suffered a major supplier failure as a result of the
1997 Aisin fire which rendered one of its suppliers incapable of
fulfilling Toyota's orders. In the US the 1992 railway strikes
resulted in General Motors having to shut down a 75,000 worker plant
temporarily as they had no inputs flowing in to the factory.
[edit] Transaction Cost Approach
JIT reduces inventory in a firm, however unless it is used throughout
the supply chain, then it can be proposed that firms are simply
outsourcing their input inventory to suppliers (Naj 1993). This effect
was investigated by Newman (1993) who found that on average suppliers
in Japan charged JIT customers a 5% price premium.
[edit] Environmental concerns
During the birth of JIT multiple daily deliveries were often made by
human powered bicycle, however with increases in scale has come the
adoption of vans and lorries for these deliveries. Cusumano (1994) has
highlighted the potential and actual problems this causes with regard
to gridlock and the burning of fossil fuels. This violates three JIT
wastes: 1) Time; wasted in traffic jams 2) Inventory; specifically
pipeline (in transport) inventory and 3) Scrap; with respect to petrol
or diesel burned while not physically moving.
[edit] Price volatility
JIT implicitly assumes a level of input price stability such that it
is not desirable to inventory inputs now at today's prices. Where
input prices are expected to rise storing inputs may be desirable.
[edit] Quality volatility
JIT implicitly assumes that the quality of available inputs remains
constant over time. If not firms may benefit from hoarding high
quality inputs.
[edit] Demand stability
Karmarker (1989) highlights the importance of relatively stable demand
which can help ensure efficient capital utilisation rates. Karmarker
argues that without a significant stable component of demand, JIT
becomes untenable in high capital cost production.
[edit] Implementation
[edit] Effects
Some of the initial results at Toyota were horrible, but in contrast
to that 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
delay.
Also, many vehicles began to be built to order, completely eliminating
the risk they would not be sold. This dramatically improved the
company's return on equity by eliminating a major source of risk.
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, the company 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. But by
the end of the first month, the rate had fallen to a few line stops
per day. After six months, line stops had so little economic effect
that Toyota installed 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 has since been widely emulated.
The Just in Time philosophy was also applied to 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 establishment.
[edit] Benefits
As most companies use an inventory system best suited for their
company, the Just-In-Time Inventory System (JIT) can have many
benefits resulting from it. The main benefits of JIT are listed below.
1. Set up times are significantly reduced in the warehouse. Cutting
down the set up time to be more productive will allow the company to
improve their bottom line to look more efficient and focus time spent
on other areas that may need improvement.
2. The flows of goods from warehouse to shelves are improved.
Having employees focused on specific areas of the system will allow
them to process goods faster instead of having them vulnerable to
fatigue from doing too many jobs at once and simplifies the tasks at
hand.
3. Employees who possess multiple skills are utilized more
efficiently. Having employees trained to work on different parts of
the inventory cycle system will allow companies to use workers in
situations where they are needed when there is a shortage of workers
and a high demand for a particular product.
4. Better consistency of scheduling and consistency of employee
work hours. If there is no demand for a product at the time, workers
don't have to be working. This can save the company money by not
having to pay workers for a job not completed or could have them focus
on other jobs around the warehouse that would not necessarily be done
on a normal day.
5. Increased emphasis on supplier relationships. No company wants a
break in their inventory system that would create a shortage of
supplies while not having inventory sit on shelves. Having a trusting
supplier relationship means that you can rely on goods being there
when you need them in order to satisfy the company and keep the
company name in good standing with the public.
6. Supplies continue around the clock keeping workers productive
and businesses focused on turnover. Having management focused on
meeting deadlines will make employees work hard to meet the company
goals to see benefits in terms of job satisfaction, promotion or even
higher pay.
[edit] Problems
[edit] Within a JIT System
The major problem with Just In Time operation is that it leaves the
supplier and downstream consumers open to supply shocks and large
supply or demand changes. For internal causes this was seen as a
feature rather than a bug by Ohno, who used the analogy of lowering
the level of water in a river in order to expose the rocks to explain
how removing inventory showed where flow of production was
interrupted. Once the barriers were exposed, they could be removed;
since one of the main barriers was rework, lowering inventory forced
each shop to improve its own quality or cause a holdup in the next
downstream area. One of the other key tools to manage this weakness is
production levelling to remove these variations. Just In Time is a
means to improving performance of the system, not an end.
With very low stock levels meaning that there are shipments of the
same part coming in sometimes several times per day, Toyota is
especially susceptible to an interruption in the flow. For that
reason, Toyota is careful to use two suppliers for most assemblies. As
noted in Liker (2003), there was an exception to this rule that put
the entire company at risk by the 1997 Aisin fire. However, since
Toyota also makes a point of maintaining high quality relations with
its entire supplier network, several other suppliers immediately took
up production of the Aisin-built parts by using existing capability
and documentation. Thus, a strong, long-term relationship with a few
suppliers is preferred to short-term, price-based relationships with
competing suppliers. This long-term relationship has also been used by
Toyota to send Toyota staff into their suppliers to improve their
supplier's processes. These intervention have now been going on for
twenty years and result in improved margins for Toyota and the
supplier as well as lower final customer costs and a more reliable
supply chain. Toyota encourages their suppliers to duplicate this work
with their own suppliers.
[edit] Within a raw material stream
As noted by Liker (2003) and Womack and Jones (2003), it would
ultimately be desirable to introduce synchronised flow and linked JIT
all the way back through the supply stream. However, none of them
followed this in detail all the way back through the processes to the
raw materials. With present technology, for example, an ear of corn
cannot be grown and delivered to order. The same is true of most raw
materials, which must be discovered and/or grown through natural
processes that require time and must account for natural variability
in weather and discovery. However the part of this that is currently
viewed as impossible is the synchronised part of flow and the linked
part of JIT. It is for the reasons stated that raw materials companies
decouple their supply chain from their clients demand by carrying
large 'finished goods' stocks. However both flow and JIT can be
implemented in isolated process islands within the raw materials
stream, the challenge then becomes to achieve that isolation by some
means other than the huge stocks they carry to achieve it today.
It is because of this almost all value chains are split into a part
which makes-to-forecast and a part which could, by using JIT, become
make-to-order. Often, historically, the make-to-order part has been
within the retailer portion of the value chain. Toyota's revolutionary
step has been to take "Piggly Wiggly's" supermarket replenishment
system and drive it back to at least half way through their automobile
factories. Their challenge today is to drive it all the way back to
their goods-inwards dock. Of course the mining of iron and making of
steel is still not done specifically because somebody orders a
particular car. But recognising that JIT could be driven back up the
supply chain has reaped Toyota huge benefits and a world dominating
position in their main industry.
It should be noted that the advent of the mini mill steelmaking
facility is starting to challenge how far back JIT can be implemented,
as the electric arc furnaces at the heart of many mini-mills can be
started and stopped quickly, and steel grades changed rapidly.
[edit] Oil
It has been frequently charged that the oil industry has been
influenced by JIT (see here (2004), here (1996), and here (1996)). The
argument is presented as follows:
The number of refineries in the United States has fallen from 279
in 1975 to 205 in 1990 and further to 149 in 2004. As a result, the
industry is susceptible to supply shocks, which cause spikes in prices
and subsequently reduction in domestic manufacturing output. The
effects of hurricanes Katrina and Rita are given as an example: in
2005, Katrina caused the shutdown of 9 refineries in Louisiana and 6
more in Mississippi, and a large number of oil production and transfer
facilities, resulting in the loss of 20% of the US domestic refinery
output. Rita subsequently shut down refineries in Texas, further
reducing output. The GDP figures for the third and fourth quarters
showed a slowdown from 3.5% to 1.2% growth. Similar arguments were
made in earlier crises.
Beside the obvious point that prices went up because of the reduction
in supply and not for anything to do with the practice of JIT, JIT
students and even oil & gas industry analysts question whether JIT as
it has been developed by Ohno, Goldratt, and others is used by the
petroleum industry. Companies routinely shut down facilities for
reasons other than the application of JIT. One of those reasons may be
economic rationalization: when the benefits of operating no longer
outweigh the costs, including opportunity costs, the plant may be
economically inefficient. JIT has never subscribed to such
considerations directly; following Waddel and Bodek (2005), this ROI-
based thinking conforms more to Brown-style accounting and Sloan
management. Further, and more significantly, JIT calls for a reduction
in inventory capacity, not production capacity. From 1975 to 1990 to
2005, the annual average stocks of gasoline have fallen by only 8.5%
from 228,331 to 222,903 bbls to 208,986 (Energy Information
Administration data). Stocks fluctuate seasonally by as much as 20,000
bbls. During the 2005 hurricane season, stocks never fell below
194,000 thousand bbls, while the low for the period 1990 to 2006 was
187,017 thousand bbls in 1997. This shows that while industry storage
capacity has decreased in the last 30 years, it hasn't been
drastically reduced as JIT practitioners would prefer.
Finally, as shown in a pair of articles in the Oil & Gas Journal, JIT
does not seem to have been a goal of the industry. In Waguespack and
Cantor (1996), the authors point out that JIT would require a
significant change in the supplier/refiner relationship, but the
changes in inventories in the oil industry exhibit none of those
tendencies. Specifically, the relationships remain cost-driven among
many competing suppliers rather than quality-based among a select few
long-term relationships. They find that a large part of the shift came
about because of the availability of short-haul crudes from Latin
America. In the follow-up editorial, the Oil & Gas Journal claimed
that "casually adopting popular business terminology that doesn't
apply" had provided a "rhetorical bogey" to industry critics.
Confessing that they had been as guilty as other media sources, they
confirmed that "It also happens not to be accurate."