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ities. Due to this, the idle material is accumulated. There is
not a good control of the internal logistic and this problem
cannot be tackled only though mathematical programming.
To get the correct replacement of material, it is necessary to
use a system that improves the times of supply. This could
be made with an efficient and effective standardized routing
and a conveyor (milkrun) to transport the trays between the
workstations. Milkrun implementation will be realized in
May. It is very important to control the state of the process
that is why it is decided to establish two new VSM in May
and August.
6.1 First improvement: kanban system
The implantation of a kanban system responds to the need
for reducing stocks. The production line requires a quick
detection of potential problems at the different work-
stations, not identified in the stocks, reducing to a minimum
the number of parts affected. The line includes several
stages of preassembly and treatment of some components
before final assembly, a rapid flow of material would
suppose major capacity of reaction to quality problems of
production.
With a classic production system, parts are processed at
the speed that allows process capacity, without considering
that the following processes could be slower or to go so far
as to stop. When this happens, there exist a few bottlenecks
in which the material accumulates, incurring in different
situations:
– Stored material consumption does not guarantee
FIFO, so the traceability gets lost.
– Previous process could be producing defective pieces
and storing them without detecting the problem, and
until the following process does not use these
component parts, the problem does not come evident.
All the materials produced with these defective pieces
will have to be reworked or eventually scraped.
– The risk of stopping all the former processes due to a
stock breakage of conform pieces.
Observing previous situations, it is possible to affirm
that the accumulated problems and errors can cause worse
difficulties, and they even can go so far as to affect final
client and it is possible to sum up in a chain of losses and
inefficiencies. Kanban is an economic and effective
solution to control material involved in different processes.
In this case, a first important factor is the origin of
suppliers, most of them German, so frequent deliveries
become costly. Due to the high number of variants in the
final product, the storage of large lot of pieces of many
different references should be avoided. A huge warehouse
space and a low rotation (cash flow) are not feasible. As a
first solution, an intermediary service of logistics is hired
next to the factory, to storage in big volumes with frequent
Fig. 3 Shelve with kanban cards
Fig. 4 Kanban card
Int J Adv Manuf Technol (2009) 43:949–958 953mailing of material. The idea was to entrust storage to an
external logistic operator.
With this service, the quantity of material in flow is
reduced, but the problem still appears at the time of
realizing orders of material from the factory. It was
established for safety specifications that the material had
to be served with the original packing of the provider,
without external manipulations. Components do not come
packed from equal form, not with equal quantities. Some of
them are received in hermetic bags, others in not reusable
shelves, etc. This was a difficulty added at the time of
realizing orders, since the frequency of achievement of
orders was not the same with all the components. To avoid
excess of material in the limited space of the one that was
getting ready, shelves were made to place the material (see