transformation to lean manufacturing by an automative component

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Please cite this article in press as: D. RAJENTHIRAKUMAR, P.R. THYLA International Journal of Lean Thinking (2011)

International Journal of Lean Thinking Volume 2, Issue 2 (December 2011)

Lean Thinkingjournal homepage: www.thinkinglean.com/ijlt

Transformation to Lean Manufacturing By an Automative Component Manufacturing Company

D. Rajenthirakumar* Department of Mechanical Engineering,

PSG College of Technology, Peelamedu Coimbatore,

641 004,Tamil Nadu, India E-mail Adres: [email protected]

P.R. Thyla Department of Mechanical Engineering,

PSG College of Technology, Peelamedu Coimbatore,

641 004,Tamil Nadu, India

A B S T R A C T K E Y W O R D S

A R T I C L E I N F O

Lean manufacturing, Value stream mapping (VSM),

Kaizenß

Received 09 May 2011

Accepted 11 May 2011

Available online 19 May 2011

Lean manufacturing is an applied methodology of scientific,

objective techniques that cause work tasks in a process to be

performed with a minimum of non-value adding activities. It has

been increasingly adopted as a potential solution for many

organizations, particularly within the automotive (Womack et al.

1990; Jones, 1999) and aerospace (Abbett et al. 1999; Womack

and Fitzpatrick, 1999) manufacturing industries. This work

addresses the implementation of lean principles in an automotive

component manufacturing company with a focus on tube sub-

assembly line. The main objective is to develop several strategies

to eliminate waste on the shop floor. This paper describes how

the value stream mapping (VSM) and other suite of lean tools

such as kaizen can be used to map the current state of a

production line and design a desired future state.

________________________________

* Corresponding Author

1. Introduction

Lean manufacturing is one of the initiatives that many major businesses have been trying to

adopt in order to remain competitive in an increasingly global market. The focus of the approach is

on cost reduction by eliminating non value added activities. Originating from the Toyota

Production System, many of the tools and techniques of lean manufacturing have been widely used

in discrete manufacturing (Liker, 1998; Womack and Jones, 1996). Applications have spanned

many sectors including automotive, electronics, white goods, and consumer products

manufacturing (Womack and Fitzpatrick, 1999).

In order to achieve the improved market share and compete with their global counterparts,

automotive component manufacturing industries in India necessarily need to improve productivity

while ensuring lower cost and world class quality. However, it is strongly believed that unnecessary

capital investment is not going to solve the problem; rather, this will turn out to be a waste in the

long run. In this direction, the implementation of lean principles is highly recommended, in order

to identify the areas generating waste; thus, it further facilitates the optimization of the operating

conditions in a minimal investment.

Please cite this article in press as: D. RAJENTHIRAKUMAR, P. R. THYLA International Journal of Lean Thinking (2011)

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This paper presents a case study of a large-scale automotive component manufacturing industry which

needs to improve the productivity in one their tube sub-assembly lines. The work focuses on the

implementation of lean principles and to develop different strategies to eliminate waste.

2. Brief Literature review

Lean manufacturing whish derived from Toyota Production System is a philosophy for structuring,

operating, controlling, managing, and continuously improving industrial production systems (Sahoo et al.

2008). Some of the standard lean tools, like VSM, production smoothing (heijunka), continuous

improvement (kaizen), 5S, single-minute die exchange, total quality management, just-in-time, etc., have

been conceived by TPS. The goal of lean manufacturing is to minimize waste in terms of non-value-added

activities, such as waiting time, motion time, set-up time, and WIP inventory, etc. (Liker, 1998).

The successful application of various lean practices had a profound impact in a variety of industries,

such as aerospace, computer and electronics manufacturing, forging company (Liker, 1998) process

industry (steel), and automotive manufacturing (Macduffie et al. 1996). Their methodology is similar,

using lean tools, and they are adapted to the study variables, but the improvement point and the results

achieved are different. Considering the available literature, the present work is the first attempt that

explores the degree of use of lean principles in automotive component manufacturing industry and

provides direction for future continuous improvement.

3. Problem environment

The objective of this paper is to use a case-based method to demonstrate how lean manufacturing

principles when used appropriately, can help the industry eliminate waste, improve productivity and

product quality, reduce lead time and obtain better overall financial and operational control. A large scale

automotive component manufacturing company’s tube sub-assembly line is used to illustrate the method

followed.

The company produces drag links, centre links and tie rods for India’s major car manufacturing

companies. The typical operations involved for making the CDS and CEW: 50*6, 40*5, 45*4.5, 26*5 types

of tube are tube heating, squeezing single and double bending. The various component groups handled

by the product assembly line are double side squeezed tube, single side squeezed tube, single bending

with and without squeezing and double bending with and without squeezing. Fig. 1 shows the typical

products handled in the assembly line. Table 1 summarizes the overall nature of the assembly line.

D. RAJENTHIRAKUMAR, P.R. THYLA/International Journal of Lean Thinking Volume 2, Issue 2 (December 2011)

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Figure 1. Typical products handled by the line

Table 1. Summary of the assembly line characteristics

Sl. No. Description Data

1. Nature of production system Batch production

2. Set-up time

Heating 30 min

Squeezing 45 min

Bending 50 min

3. Transfer of material Manual

4. Mean time between failure 6 days

5. Total man power 18 per day

6. Work-In-Progress 2200 units

7. Material travel distance 62 ft

8. No of machines involved 7

9. Space occupied 899 sq. ft.

The company was experiencing severe pressures, both internally and externally, to improve the

productivity of the assembly line. In recent years, the company has tried many options with huge capital

investments; however, the results achieved were not significant compared to the investment made. In the

pursuit of consistency, the management decided to implement lean principle. After several brain storming

and a thorough study of the shop floor, it was observed that the tube subassembly line consists various

forms of non-value-adding activities as follows:

High lead time

Accumulation of high inventory

Unnecessary material flow

High material travel distance

Poor Mean-Time-Between-Failure (MTBF)


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Under-utilized man power

In order to implement lean principles, a task team was formed with people from different department,

all having wealthy knowledge and information pertaining to production, machinery, scheduling and

planning. The prime objective is to develop different strategies to reduce the level of non-value activities

present in any form by implementing the various lean tools. The research targets for the task team are as

follows:

Reducing change-over time to 10 minutes

Increasing the line productivity by 25%

Reducing the WIP to 200 units

Improving the material flow

4. Implementation and results

The lean tool VSM applied as a method to lead the activities. In order to visualize the non-value-added

activities it was decided to first construct the current state value map.

4.1 Constructing the current state value stream map

Relevant information from various departments is collected to construct the current state value stream.

Information related to the assembly line, such as cycle time at each work stations, machine down time for

each process, inventory, change-over time, set-up time, number of workers and operational hours per day

are also collected and documented properly. Table 2 summarizes the major activities associated with tube

subassembly line. To complete the value map, a timeline is added at the bottom of the map recording the

total processing time and the value-added time. Finally, the value stream map for the current state is

constructed as shown in Fig. 2.


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Table 2. Major activities in the tube subassembly line

Sl. No. Activity Description

1

Cup pressing GWI

2

Tube heating

3

Squeezing

4

Cup pressing GWO

5

Tube bending


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Figure 2. The current state value stream map

From the current state value map, it is found that only 101 seconds were value added activities, compared

to 80640 seconds of non-value-added activities. The following sub-sections describe a planned and

integrated approach adopted to reduce the non-value-added activities.

4.2 Reducing change-over time

After a detailed study and analysis of the standard work procedure and thorough investigation on the

assembly line, it was found that the change-over time contributes significantly to the total processing time

(Fig. 3). Reducing the change-over time in any manufacturing system is a continuous improvement

process. The methodology adopted for reducing the change-over time reduction is shown in Fig. 4.


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Figure 3. Change-over time analysis

Figure 4. Methodology adopted for change-over time reduction

4.3.1 Tube bending process – Time study analysis

The various elements associated with change-over time are identified and different strategies are

implemented to reduce the change-over time. The standard work elements and work element time is

measured, documented and classified as internal and external as shown in Table 3. In order to reduce the

total change-over time, various strategies such as data documentation, method and time study, review of

standard work procedure and continuous monitoring are adopted. Fig. 5 summarizes the results of time

study.

Figure 5. Time study summary

Change-over time reduction


during bending

Time study analysis

Kaizen Process improvement

Modified inspection Fixture standardisation


during heating

Process standardisation

Squeezing set-up time reduction

Kaizen Improved die design


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Table 3. Standard work elements classification

Through brain storming conducted with the employees, a list of non-value adding activities are

identified. The Pareto chart of the non-value adding activities along with their time is shown in Fig. 6 and

Table 4 shows the improvement activities identified by the brainstorming.

Table 4. Improvements activities to eliminate NVA

Sl. No. Improvement activity NVA activity (number) addressed

1 Standardization of fixtures 8,9

2 Standardization of fasteners and accessories 2, 3, 5, 11, 14, 16, 17

3 Designated roller fixture stand with rolling trolley 6, 7, 10, 13, 18

4 Locations for trolley 1, 12

5 Standardization of height blocks 4, 15


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Figure 6. Pareto chart showing NVA along with their processing time

4.3.1.1 Kaizen

Keeping the change-over time reduction during bending process as an objective, the kaizen procedure

followed is shown in the flow chart (Fig. 7).

Step – 1: Form the team and gather information

In this step, the facts of the process and the direction for improvement are examined. This information

will be used in the next step, the current process, to gather information about the process.

Step – 2: Description of the process

Utilizing the kaizen methodology, the team will select the aspect of the process most in need of

improvement.

Step – 3: Decide goal of the team

After gathering detailed information about the current process, the kaizen team identified the goal, which

took into consideration the directions of the management. In this case, the team decided to focus on

improving the method of tube bending process. This improvement was expected to reduce 50% of the set

up time of that process. This reduction of time was, in turn, expected to reduce the change-over time and

manual effort.

Step – 4: Alternate methods – 1. Standardization of height blocks 2. Adjustable socket locator

Following the Kaizen methodology, the Kaizen team developed twenty ideas to improve the bending

process. Fig. 8 and Fig. 9 demonstrate two such alternatives at a glance.

Step – 5: Evaluate and select the best solution

The thirteen best kaizen among the twenty solutions are selected to improve the tube bending process

took into consideration the directions of the management.


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Figure 7. Flow chart of kaizen procedure

Figure 8. Kaizen 1: Standardization of height blocks


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Figure 9. Kaizen 2: Adjustable socket locator

Step – 6: Simulation and evaluation

To confirm the possibility of implementing the methods by the Kaizen team, a simulation was undertaken.

The team decided to see if it was possible to reduce the change over time with reduced human effort. To

do this, the team used Arena, one of the most powerful simulators with the animation function and an

easy-to-use interface. The results show that the change-over time during the bending process is reduced

from 2815 sec to 755 sec which is 73% change-over time reduction.

Step – 7: Accomplishments

The kaizen team also developed a new improved off-set checking method (Fig. 10) for the tubes. Table 5

summarizes the results achieved by this improved method.

(a) Before kaizen (b) After kaizen

Figure 10. Kaizen Accomplishment: New improved tube off-set checking method


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Table 5. Improvements after new off-set checking method

Sl. No. Activity Processing time in seconds

Before implementation After implementation

1 Tube off-set checking 300 30

2 Lifting the previous fixture to the trolley 240 80

3 Moving the unloaded fixture to stand 150 60

5. Other improvements through lean principles

The summary of other improvements and financial benefits obtained after implementing lean principles in

the manufacturing shop floor is given in the Table 6.

Table 6. Summary of other improvements and benefits

Sl.

No. Description

Before lean

implementation

After lean principles

implementation Financial benefits

1 Production per day 1320 units 1740 units 32% productivity

improvement

2 Man power utilization

per day 18 14 3.6 Lakhs per annum

3 Machine utilization 7 6 6 Lakhs

4 Cost of power Rs. 1.3 per unit Rs. 0.3 per unit 9.6 Lakhs per annum

5 Space utilization 899 square feet 620 square feet 279 square feet space saved

6 Work-In-Process 2200 units 200 units Reduction of inventory by

2000 units

6. Concluding remarks

Due to increased customer expectations and severe global competition, the automotive component

manufacturing companies are desperately trying to improve productivity at lower cost and still retain

excellent product and service quality. Under these circumstances, the implementation of lean principles

improves the production environment with moderate investment. This case study carries evidence of

genuine advantages when applying lean principles to the manufacturing shop floor. Furthermore, the

benefits of lean are evident from the improved production output.


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transformation to lean manufacturing by an automative component

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