In the current era of globalization, automotive industries are adopting new
tools and techniques to produce goods to compete and survive in the market.
The most daunting issue faced by manufacturers today is how to deliver their
products or materials quickly at low cost and good quality. One promising method
for addressing this issue is the application of lean manufacturing principles
and techniques. Lean manufacturing or lean production, simply known as lean,
is production practice which regards the use of resources for any work other
than the creation of value for the end customer, is waste and thus a target
for elimination (Womack et al., 1990). For many,
lean manufacturing is the set of tools that assist in the identification
and steady elimination of waste (muda). The main tools of a manufacturing program
are value stream mapping, 5S, TPM, SMED and Six Sigma. These tools focus on
certain aspects and areas of the manufacturing process to eliminate waste and
improve quality while production time and cost are reduced. The waste reduction
philosophy considers the change over time as a non-value added activity. Change
over time that is illustrated in Fig. 1 is defined as a method
of analysing and reducing the time needed to change a process from producing
one good part to producing the next good part (Ulutas, 2011).
In the scope of lean manufacturing, an important problem needed to be solved.
Because lean manufacturing requires small batch sizes and high product variation
a new method had to be developed to reduce the setup times.
|| Representation of change over time
In 1985 Dr. Shigeo Shingo introduced his methodology called Single Minute Exchange
of Die (SMED) (Cakmakci and Karasu, 2002). SMED is a
scientific approach to setup time reduction that can be applied in any factory
and also to any machine (Shingo, 1985). The ultimate goal
of SMED is to perform machine setup and changeover operations in less than 10
min. Several practitioners have proved that this method really works in practice
and in some situations reductions of higher than 90% setup time are achievable
(Van Goubergen and Van Landeghem, 2002). With the application
of SMED, improvements were substantial with initial data showing reduction of
setup time ranging from 25% to as high as 85%. With the reduced setup time,
production flexibility expanded as it was able to afford more frequent product
mix changes. In addition, machine utilization and equipment went up with the
reduced setup (Gilmore and Smith, 1996; Tharisheneprem,
2008; Moxham and Greatbanks, 2001). The SMED technique
is used as an element of TPM and continuous improvement process
in efforts of reaching lean manufacturing (Ogaji et al.,
|| Evaporator core process flow
Case studies about setup reduction at different manufacturing environments
take place in some texts. In addition, the technique is evaluated about its
sequential implementation approach (Cakmakci, 2009).
In light of the literature survey, the present study is the first attempt that
explores the degree of use of lean practices in the manufacturing of evaporator
core in an automotive industry and provides direction for future research.
Process detail: This study concentrates on the evaporator core building of the model car-PA. The evaporator coil in an air conditioning system is responsible for absorbing heat. As air (can also be water in a chiller) passes over the evaporator coils a heat exchange process takes place between the air and the refrigerant. The refrigerant absorbs the heat and as it absorbs heat is flashed to a vapour. The air conditioner evaporator conditions the air in two ways why it is typically operating below the dew point. It causes sensible cooling and it causes latent heat removal. The latent heat removal is the process of drawing moisture out of the air and the sensible cooling is dropping the temperature of the air.
Figure 2 shows the Evaporator core process flow, starts from the press and fin mill to the susring unit, from where it is made to pass to the furnace then to the brazing and gauging section finally to the inspection area. Completed evaporator core is shown in Fig. 3, after the entire process is over it is sent to the storage where it will be retrieved latter to form a part of the Heating, Ventilating and Air Conditioning unit (HVAC).
|| Evaporator core
Data collection: A statistical data collection method for measuring Fagor press operation setup time was used in this study to summarise and describe the data. Standard operation procedure is reviewed briefly before setting up the data collection table. The next step is to create a data collection table prior to collecting data and the time taken was measured using a stopwatch. Based on the actual production, data was collected and recorded on a shift basis by different types of time loss from the Fagor press operation. These methods helps to identify the main contributor to high time loss in the Fagor press and help to visualise and better understand the root causes and finding possible solutions to the problems.
Application of SMED techniques: Setup operation is defined as the preparation
or post adjustment that is performed once before and once after each lot is
processed (Shingo, 1985). Shingo divides the setup operation
into two parts:
||Internal setup: The setup operation that can be done
only when the machine is shut down (attaching or removing the dies)
||External setup: The setup operation that can be done when the machine
is still running
|| SMED conceptual stages and practical techniques
|| Current percent of setup steps
These operations can be performed either before or after the machine is shut
down; for example, getting the equipment ready for the setup operation can be
done before the machine is shut down. The three main steps of SMED, also given
in Fig. 4, can be summarized as follows:
||Separating internal and external setup
||Converting internal setup to external setup
||Streamlining all aspects of the setup operation
Data analysis: The analysis of data and information gathered led to significant improvement carried out in mechanical improvement and organisational improvement. Comparison result before and after SMED implementation was extensively reviewed. The operation of removing a die will be further split in to this format as listed in the Table 1.
IMPLEMENTATION AND RESULTS
Basically, Fagor Press is used to manufacture the evaporator plates from aluminium sheets. This press is about 400 ton, 34 feet high and 18 feet long. The tool die comprises of two parts the upper die and the lower die. The upper die has the projected part and the lower die has the receiving part. Usually the tool die consist of the various process, as the aluminium sheet is made to pass through the Fagor press there is a series of various shape forming and cutting so that finally when the process is over a complete and a finished evaporator plate will come and fall, Fig. 5 shows the different types of evaporator plates.
Analysing setup time: The regular tool changing procedure of 400 ton
Fagor press took about 12 steps and 40 min to set the die in proper position
and start out the process. Hence, through literature survey, have put in forth
the advanced technique of lean Manufacturing called the SMED to simplify the
tool changing process and also increase the production size of the Fagor press.
After all the process is over, the regular production process starts from here:
|| Task operation: The task been performed by the operator
to perform the tool changeover process
|| Actual time: The time that is been noted while the operation is
been performed (In-Internal time, Ex-External time)
|| Improvement: After the necessary changes the tasks performed
|| Target time: The time noted with the implementation of the improvement
(In-Internal time, Ex-External time)
|| Current changeover time
|| Change over time after 1st SMED attempt
|| Completed SMED table
|| Evaporator plates
Table 2 shows the actual change over time practiced in the industry. Then after the 1st SMED attempt, the time is reduced from 40-18 min and is shown in Table 3. Then took another chance and planned to further decrease the tool changeover time. In step 3, increased the overhead fixture speed and did the same procedure, the time further got reduced from 2.07-1.10 min. In step 4 the new die is placed in position, this cancelled out the new die search time and old die change time. The time further got reduced from 2.13-1.17 min. In step 6, proper positioning of tool die using chain drive nullified locator checking process. In step 9, told the operator operating on the aluminum mill to work a little faster. They cut down the time from 8-5 min, though this step is not taken for consideration, because this process has been started when the tool changeover process starts. Rest of the procedure is the same as that of the first time. In this 2nd SMED attempt, the time is reduced from 18-12 min. The tool changeover time for an actual process was about 40 min which after implementing the 1st SMED got reduced to about 18 min and after the 2nd SMED got further reduced to 12 min.
The following Table 4 shows in detail about the 3 different
shifts and there working time period in minutes. In this case consider 1 shift
is 480 min of work time period but in which 36 min w ill be for tool die changing
procedure and 444 min of press run time.
|| SMED after implementation
This will be a normal procedure which industry follows. After implementing
1st SMED, changes the tool changeover time to 18 min and press run time to 462
min. which further got reduced to 12 min of tool changeover time and 468 min
of press run time after implementing 2nd SMED, shown in Fig. 6.
Basic calculation and tabulation:
|| Total no of shifts = 3
|| Each shift = 8 h = 480 min
|| No. of components produced in 1 min = 70 pieces
|| No of components produced in 1 shift = 440 pieces
|| No. of defective pieces in 1 shift = 65
The lean technique, SMED, was implemented and a significant result was achieved.
SMED methodology was applied to prepare an optimal standard procedure for changeover
operations on Fagor press. Based on a series of time study data collected during
the setup activities in the Fagor press, a comparison of results and achievements
before and after the SMED implementation was made to measure the effectiveness
of SMED to reduce setup time. The goal to reduce machine downtime during the
setup operations and reduction in setup time makes it possible to increase manufacturing
system flexibility to manufacture a variety of products. By implementing the
SMED techniques, the total time taken to perform setup activities at Fagor press
was reduced by from 40-12 min i.e., 28 min reduced and production rate has been
increased from 92200-98080 pieces i.e., 5800 pieces increased. Other benefits
achieved from SMED implementation are quick response to customers demand, increases
workers motivation, improved workers safety and health and parallel
operation system. Further studies in the facility may include 5S and Kaizen
studies for internal setup. Alternative ways to shorten internal setups can
be searched in detail. In order to eliminate adjustment steps, trial and errors
should be minimized. Finally, the complete success of the application of lean
viewpoint in the long run will depend on close teamwork between the shop floor
personnel and the management.