application of lean manufacturing in an industrial company
TRANSCRIPT
Page 1 of 9
Application of Lean Manufacturing in an Industrial Company -
Improvement of the line feeding system
Bruno Miguel Teixeira Costa
Instituto Superior TΓ©cnico, Universidade de Lisboa, Portugal
November 2017
Abstract: The current era is defined by high industrial and business competitiveness. Due to the
increasingly globalized market, the variety of products and competitors is increasing, leading
companies to look for solutions to become more competitive. Lean Manufacturing is a way of
thinking, with methodologies and tools that aim to eliminate waste and increase the
competitiveness.
This thesis was developed in a company of the automotive sector. The goal was to apply the Lean
tools, to reduce waste on the assembly line.
The initial diagnosis made to the line led to the conclusion that a large part of the waste was due
to the inexistence of an effective line feeding system. So, a new system was created. To this end,
was created a supermarket area, divided into two zones, one for picking of dedicated cars and
another for boxes. The system would work in pull, using a kanban system. The components would
be transported to the line by the mizusumachi. The layout of the border of line also had to be
redesigned, presenting improvements in the operation and reducing waste.
The implementation of this project allowed the company, not only an overall improvement of the
process, but also a significant cost reduction.
Keywords: Lean Manufacturing, Supermarket, Kanban, Mizusumachi
1. Introduction
We live in an era of high technological
evolution, where the product cycles are
increasingly shorter, due to the growing
consumerism.
This is particularly relevant in the automotive
industry, where the products are very
complex and customizable. To be
competitive in this sector, itβs necessary to
have a flexible production system, capable
of produce a large variety of products, using
the least amount of resources possible.
To achieve that, the companies look for
ways to be more efficient. This is where the
Lean philosophy quicks in.
This works aims to implement Lean
methodology and tools, to reduce waste on
the assembly line, increasing efficiency and
decreasing costs.
2. Bibliographic research
The concept of lean manufacturing was
introduced by Womack, Jones and Roos, on
the book βThe Machine That Changed The
Worldβ [1].
On the book βLean Thinkingβ, Womack and
Jones, define the five lean principles [2]:
β’ Value β Define whatβs value from
the clientβs point of view;
Page 2 of 9
β’ The value stream β Identify all the
operations along the process chain;
β’ Flow β Make the process flow;
β’ Pull β Make only what is pulled by
the client;
β’ Perfection β Strive for perfection
thru continuous improvement.
The Lean philosophy aims to eliminate
waste. Taiichi Ohno defined seven types of
waste [3]:
1. Overproduction;
2. Time on hand (waiting);
3. Transportation;
4. Processing itself;
5. Stock on hand (inventory);
6. Movement;
7. Making defective products.
Just-in-time (JIT) β Working in JIT means
producing only what is needed, when its
needed. Anything over that is viewed as
waste [4].
In this work were used the fowling lean tools:
5S β The 5S methodology aims to improve
the workstation environment. The S comes
from five Japanese words (here translated to
English): Sort, Straighten, Shine,
Standardize, Sustain.
Kanban β Kanban is the Japanese word for
card. In a Kanban system, the card acts as a
replenishment order, pulling the production.
Only is produced what is consumed and
which container only was one reference [5].
Junjo β Junjo is the Japanese word for
sequence. In a junjo system the parts are
supplied in the sequence by which they will
be consumed [5].
Mizusumachi β Mizusumachi means water
spider. The mizusumachi is the operator who
does the internal transportation of goods,
using a standard fixed cycle route [5].
Supermarket - A supermarket is an area
where the picking of goods is easy. The
supermarket area has a fixed location for
every part number, easy picking access and
keeps the FIFO principle [5].
3. Case study and diagnosis
This work was performed at Benteler
Palmela, who manufactures products for VW
Autoeuropa.
The goal of this work was to improve the rear
axle assembly line, thru an implementation
of a line feeding system.
The first step to perform this work was the
line diagnosis. The rear axle assembly line
works in JIT, producing all the rear axles,
from all the models produced at Autoeuropa.
The line assembled three kinds of chassis,
having seven manual workstations and
seven automatics, in a total of eight
operators, as showed in figure 1.
After an initial overview of the whole process
were identified a few problems:
β’ Border of line full and disorganized;
β’ Parts too far from the operator;
Figure 1 - Representation of the assembly line
Page 3 of 9
β’ Some parts are supplied to the line
by the line operator himself;
β’ Most of the parts are supplied to the
line in the transportation containers;
β’ Inexistence of an efficient line
feeding system.
To verify the impact of this problems in the
line, measurements were taken and the
following results were obtained:
From the figure, we can see that the
operators spend a lot of time on two activities
with no added value, movements and
frequential activities.
Movements β To understand why the
workers spent so much time moving, a
spaghetti diagram was made, as showed in
figure 3. From that we can see that the
operators have to move a lot, to pick up the
parts they need. This happens because the
parts are too far from the line, due to the
transportation containers, that are too big.
Frequential activities β This were activities
that the workers, would perform
occasionally, like closing containers and
removing cardboard or inlets.
All the problems identified would be solved,
with an efficient line feeding system, so a
new system was created.
4. Line feeding system
The first step for creating the new system
was a logistic survey.
Logistic survey β Thru this survey, we were
able to identify all the parts that need to be
supplied, where they needed to be supplied
and how much was the demand for which
part.
Mizusumachi cycle β To scale out all the
system, we needed to define the
mizusumachi cycle. To do that we identified
which part would be the bottleneck of
system, and establish the cycle time from
there. Was decided that the cycle time would
be 20 minutes.
Kanban vs junjo β The next step was to
decide, what system would we use, Kanban
or junjo. On a Kanban system, each
container only contains one reference, while
in junjo system, a container has multiple
references, in the sequence in which they
will be consumed in the line. On a Kanban
0%
20%
40%
60%
80%
100%
Operation T. Movement T.Frequential Act. Waiting T.Control T. Time to Cycle t.
Figure 2 β Percental times per workstation
Figure 3 - Spaghetti diagram
Page 4 of 9
system, the mizusumachi only has to
exchange empty boxes by full ones. In a
junjo system the parts have to be
sequenced, which implies more complexity
and more work.
From the assembly line point of view, junjo is
better, because they receive the parts,
already in the order that they are going to
need them. Junjo also occupies less space
in the border of line. However, the junjo e
much more complex and only justifies its
application when there is a large variety of
references for the same part or when the
parts are very big. Since this wasnβt our
case, was decided to use the Kanban
system.
Methodology for calculating the quantity
of components required at the border of
the line β To calculate the number of
kanbans needed in the border of line, to
assure an uninterrupted supply, was used a
methodology from Kaizen Institute:
ππ‘π¦ πππππππ π΅ππΏ
=2 Γ ππππππ πππ ππ¦πππ
ππ‘π¦ ππ ππππ‘π πππ ππππππ+ 1 ππππππ
4.1. Supermarket
After knowing the size of the containers in
which the parts came from the supplier, was
possible to make an estimation of the area
needed to implement the supermarket.
The first solution tried, was to make a
traditional supermarket, were the parts
containers would be on the ground and the
operator would make the picking to cars or
boxes. However, soon became clear that
would be impossible, to put all the
components needed, in the area that we had
available, using this solution.
One other solution was to use a flow
supermarket. On this solution, the boxes
would be stored in a flow rack and the
containers on a rack. The mizusumachi
would only have to leave the empty boxes
and collect the full ones, without needing to
fill the boxes. Other operator would lower the
containers from the rack when needed and
fill the boxes.
The solution chosen was a mixed one. The
supermarket would be divided into two
areas, one with ground storage, for picking
to cars and one other with a flow rack for
boxes.
To implement this solution were considered
various layouts. The one adopted is on figure
4. This layout contains an area for picking
cars and parking, and an area with two racks
and a flow rack. In the figure 5, we can get a
better perspective thru a 3D representation
of the supermarket.
4.2. Dedicated cars
Some parts couldnβt be transported in boxes.
For these components were developed
Figure 4 β Supermaket layout
Page 5 of 9
specific cars to transported them to the
assembly line.
Hubs car β This car was dedicated to the
transport of hubs. These parts were heavy
and needed a specific support, to prevent
damage during transport. To avoid this, were
used the containers inlets as support. The
car itself was made from steel tube
30x30mm. The figure 6 show the project of
the car.
Brake calipers car β The restrictions for this
car, were very similar to the ones found in
the hubs car. So, a similar solution was
found, using the containers inlets as support
and the structure of the car in steel tube, as
showed in figure 7.
Discs car β The restrictions for this car
were similar to the ones on the previous
cars. However, in this case there wasnβt an
inlet that we could use. So, a specific support
had to be developed. The developed
support, consisted in a steel sheet, with slots
where the discs were fitted. To prevent
damage to the discs, a POM board was fitted
on top of the steel sheet. The structure of the
car was similar to the previous ones, as seen
on figure 8.
Figure 5 - 3D representation of the supermaket
Figure 6 - Project of the hubs car
Figure 7 β Project of the brake calipers car
Page 6 of 9
Anti-roll bars car - This car was dedicated
to the transport of anti-roll bars. To make the
car as small as possible, was decided to
transport the bars vertically, leaning against
each otherβs. The bars were supported by
two tubes on top and two on the bottom, to
make sure that they didnΒ΄t fell during the
transport. Unlike other cars, this one was
made in trilogiq tube, to be easily adjustable,
as shown in figure 9.
Chassis car β This car was dedicated to the
transport of chassis. The chassis, would be
supplied to the line already sequenced. The
car would have to be able to transport three
different types of chassis, which created the
problem of how to support them. The
solution founded, was to create a support
with a specific fitting, for each chassis. The
chassis were heavy, so the car had to be
very robust. In that sense, the car was built
in steel tube 40x40 mm. The car be seen in
figure 10.
4.3. Border of line flow racks
To supply the all the boxes to the border of
line, was necessary too built flow racks, to
place in the border of line.
OP50/OP310/OP850 β The flow racks of this
workstations were very similar. All had three
level of stock and one for empty boxes. The
global dimensions were 0,5 m by 1,1 m. In
the figure 11 is shown the flow rack of
OP310.
OP100 β This flow rack was the biggest of
the line, having capacity for nine references.
The global dimensions were 1,955m x
1,350m, as shown in figure 12.
Figura 8 - Project of the discs car
Figure 9 - Project of the anti-roll bars car
Figure 10 - Project of the chassis car
Figure 11 β Project of the flow rack of OP310
Page 7 of 9
OP450 β Due to lack of space, the flow rack
of this workstation was divided in two. The
first one had room for three references and
a global dimension of 1,455m x 0,735 m.
The second one, had room for four
references and a global dimension of
1,655m x 1,140m. Both can be seen in figure
13.
4.4. Border of line layout
After all this, was necessary to define, where
to place the cars and flow racks in the border
of line.
OP50 β This was a particularly tricky one.
We needed put in the border of line, three
cars and one flow rack. Were considered
several possibilities, but the one chosen was
the one that allowed the best flow and less
movements from the operator. This layout is
shown in figure 14.
OP100 β In this one we only had one flow
rack, so was relatively straight forward. Due
to several constrains, the only place to put
the flow rack was on the back of the
operator.
OP300/310 β On the border of line of these
workstations, we had to allocate six cars and
one flow rack. The flow rack was common,
so made sense to stay in the middle. To
minimize the movements, the best way to
place the cars was on the back of the
operators.
Figure 15 shows the layout from OP100 and
OP300/310.
OP450 β Due to the solution found for this
workstation, the layout was already defined
from the start. The operator would work in
Figure 12 - Project of the flow rack of OP100
Figure 13 - Project of the flow rack of OP450
Figura 14 β Layout OP50
Figure 15 - Layout
Page 8 of 9
the middle of the two flow racks, with them
being placed on the edges of the
workstation, as shown in figure 16.
OP 850 β In this workstation, we only had
one flow rack, so there were just two
possibilities. Or place the place the flow rack
on the back of the operator or on the side.
The choice was to place it on the side,
because that way, the operator has to move
less. This layout can be seen in figure 17.
5. Developed solutions impact
After conceiving all the system, it was time
to see the impact that the changes have had.
The first impact is visual. The changes had a
big impact on the 5S, improving the factory
standards in organization and ordination.
This is clear on the supermarket, where
everything was its place and every position
is identified. The border of line, is also
improved, with less material and better
organization.
One of the main goals of this project was to
reduce waste. This was achieved, especially
in two areas, movements and frequential
activities.
Due to the new layouts, the parts are now
much closer to the operators, which means
that the movements, are now one third of
what they were initially.
Since the components now, arrive to the
assembly line in optimized cars and boxes,
thereβs no need to close containers or
remove card board, so the frequential
activities were eliminated.
To see the influences of this changes on the
line, measurements were taken and the
following results were obtained:
Figure 18 - Percental times per workstation after
improvements
As expected, from the figure 18, we can see
a big reduction on the movements and on
the frequential activities. This means that
now the operators have a lot of time on their
hands, just waiting for the cycle time. To
solve this, we can rebalance the line.
Do to the improvements and the reduction of
waste, we can now rebalance the line,
eliminating the OP50 and the OP310,
splitting the work by the others workstations.
This means that we can also reduce the
number of operators to six, reducing costs.
If we take measurements after the
rebalance, we will obtain:
0%
20%
40%
60%
80%
100%
Operation T. Movement T.
Frequential Act. Waiting T.
Control T. Time to Cycle t.
Figure 16 β Layout OP450
Figure 17 β Layout OP850
Page 9 of 9
Figure 19 - Percental times per workstation after rebalance
As we can see from figure 19, the workers
now have much less time on their hands,
which results on an improvement of the line
efficiency.
6. Conclusion
After the diagnosis of the assembly line,
many wastes were identified. The main
cause of those wastes was the inadequate
line feeding system.
To address this, a new line feeding system
was created, reducing the wastes and
improving the efficiency of the process.
7. References
[1] J. P. Womack, D. T. Jones and D. Roos,
The Machine that Changed the World,
Simon and Schuster, 1990.
[2] J. P. Womack and D. T. Jones, Lean
Thinking, Free Press, 2003.
[3] T. Ohno, Toyota Production System:
Beyond Large-Scale Production, CRC
Press, 1988.
[4] N. J. A. e. F. R. J. R. B. Chase,
Prodution and Operations Management,
McGraw-Hill, 1998.
[5] E. Coimbra, Kaizen in Logistics and
Supply Chains, McGraw-Hill Education,
2013.
0%
20%
40%
60%
80%
100%
OP100 OP300 OP400 OP450 OP850
Operation T. Movement T.
Frequential Act. Waiting T.
Control T. Time to Cycle t.