Jurnal TA Lean SIx Sigma

Final Project Journal | Industrial Engineering Faculty

Abstract— Company X is plastic part manufacturing company with plastic injection product line as their main product line. One type of its products with the highest production and is always produced every month is FB 7084 with an average number of 441 102 units per month of production. However, company cannot reach the planned production target for this type of product FB 7084 with high levels of production planning in several periods. Therefore, improvement efforts planning are needed to identify and eliminate waste dominant occurring during the process flow using Lean Six Sigma approach. The object of this research is focused on the process of making the product FB 7084 plastic injection production floor. The research is started by making a current state map to find out the current value stream. Through the value stream mapping it is identified that lead time process is 5130.45 seconds with respective activity percentage are as follows: delay 37.35%, non value added operation 2.74%, transportation 0.03%, and value added activity 59.87%. To identify waste dominant occurring during the process waste checklist is used and it is identified that the waste dominant is waste waiting or delay that increase lead time. An improvement proposal planning is made to overcome waste dominant that occurred by implementing pull system, as well as conducting operation method improvement so that material flow can flow faster. The improvement proposal is indicated shorter process lead time that is 3529.44 seconds. From the overall process, activity with the highest percentage after the improvement is value added operation activity with percentage of 94.244, while another activity percentage : delay 5.27%, transportation 0.05%, and non value added operation 0.44%. Proposal work system application is expected the company can reach production target planned especially for the FB 7084 product.

Index Terms—Lead Time, Lean Six Sigma, Plastic Injection, Value Stream Mapping, Waste

I. INTRODUCTION OW days, customers awareness of the importance of quality is increasing. This is exactly what makes the

quality of both product quality and delivery quality, being one of the important aspects that must be considered by the company to run its business, especially for PT. X. PT. X is a manufacturing company engaged in the manufacture of plastic parts for motor vehicles and other plastic products. The main product line of PT. X is a plastic injection line that donates the largest profit contribution compared to other production lines.

The profit contribution percentage for each production line in PT. X can be seen in Figure 1.

Fig. 1 : Profit Contribution Percentage for Each Production Line

(Resource : PT. X Historical Data, 2013)

Product, in plastic injection production line, with the

highest production number is FB 7084 with an average demand 441,102 unit every month.

TABLE I

The Highest Demand Average for Plastic Injection in January 2013 – November 2013

(Resource: PT. X Historical Data, 2013)

Produk Rata-Rata Demand FB 7084 319,364 604402-VL 282,906 32413-KGH-9000 74,105 32412-MV4-0000 66,103

PT. X is faced with some problems during the production of FB 7084 product. The problems are the failure in achieving production targets and the high rate of rejection during process. The problem of the high rate of rejection will be discussed by researchers partner, Ratri Mayra Maherani, on her research entitled "Proposed Improvements to Improve Product Quality Plastic Injection to Lean Six Sigma Methods in PT. X ". While the issues to be discussed in this final project is the failure in achieving production targets.

PLASTIC INJECTION

76,45 %

WIRING 20,08 %

MACHINING 3,47 %

Improvement Proposal To Reduce Lead Time in Plastic Injection Using Lean Six Sigma Method

in PT. X Fildza Rossianti ST., M. Iqbal, ST., MM., and Andri Suryabrata, ST., Msc.

N


Fig. 2: Production Planning and Production Result of FB 7084

in January 2013 – March 2013

(Resource: PT. X Historical Data, 2013)

Based on figure 2, PT. X cannot achieve the planned production target for FB 7084 product on some periods with high levels of production planning. The failure to achieve production target can causes a decreased quality of delivery because it allows delay in delivery of products to customers.

The problem of failure to fulfill production targets is exactly what prompted the authors to develop improvements strategy in production of FB 7084, which is a product from PT. X, by reduce wasteful activities, facilitate the flow of material, distinguish between value added and non-value added activities, as well as create value added to flow smoothly and efficiently throughout the value stream process so that the lead time can be reduced.

A. Problem Formulation The formulation of the problem to be addressed in this final

project is as follows: 1. What is the dominant waste during the process? 2. How to formulated the improvement of the

production process to eliminate waste dominant in order to reduce lead time process?

B. Purpose of the Research The objectives of this research are:

1. Finding the dominant waste in every activity on the production of plastic injection.

2. Formulate the improvement of the production process to eliminate waste dominant in order to reduce lead time process.

C. Limitation of the Research The limitations In this research are as follows:

1. Process flow analyzed in this research is only FB 7084 production process.

2. Any kind of costs are not calculated in this research.

II. THEORETICAL BASIS

A. Quality “Quality is conformance to requirements or

specifications”, (Montgomery, 2009:6). Quality is very important to be considered during the production process by companies. There are some dimensions of quality:

1. Performance 2. Reliability 3. Durability 4. Serviceability 5. Aesthetic 6. Features 7. Perceived quality 8. Conformance to Standards

Every dimension define the rate of quality, either delivery quality or product quality.

B. Six Sigma Approach Six sigma is a systematic methodology that focuses on

controlling the performance of a process. According to Gaspersz and Fontana (2011:37), in Six Sigma terminology, there are several unit types of measurement used to measure the quality of a process or product. Some of them are defect rate, ppm, DPU (Defect per Unit), DPMO, and sigma value. The higher sigma values define the lower reject rate of a process.

Calculation of sigma value:

𝐷𝑃𝑈 =𝑇ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑑𝑒𝑓𝑒𝑐𝑡𝑠 𝑜𝑏𝑠𝑒𝑟𝑣𝑒𝑑

𝑡𝑜𝑡𝑎𝑙 𝑢𝑛𝑖𝑡𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑

𝐷𝑃𝑂 =𝐷𝑃𝑈

𝑇𝑜𝑡𝑎𝑙 𝑝𝑜𝑡𝑒𝑛𝑡𝑖𝑎𝑙 𝐶𝑇𝑄

𝐷𝑃𝑀𝑂 = 𝐷𝑃𝑂 ×10!

Sigma Value =1000000 − 𝐷𝑃𝑀𝑂

1000000+ 1,5

C. Lean Approach According to Gaspersz and Fontana (2011:1), Lean can be

defined as a sustained effort to eliminate waste (waste) and increase the value-added that provide value to customers (customer value).

Lean Principles: According to Hines and Taylor (2000:5) in the implementation of Lean concepts based on five principles:

1. Specify value Identify the value of the product from the customer's viewpoint and set the value of the product specifications desired by the customer appropriately.


2. Value stream analysis Identify the necessary steps, started from the design process, ordering and manufacturing of products based on the entire value stream to find waste that do not add value to the process.

3. Flow Activities during the process that add value are set to flow unimpeded from one process to another.

4. Pull System Pull system is a production processes that are based on customer demand. The objectives of pull system are to make material and information flow during the value stream became more fluently and efficient.

D. Lean Six Sigma Approach Lean six sigma method synergizes the advantages of two

existing method of quality improvement, that are Lean and Six sigma approach. With the integration of Lean and Six Sigma method, called Lean Six Sigma, will improve the performance of the business and industry through the increased speed (short cycle time) and better accuracy (zero defect). Lean approach will expose the non-value added and value added activity and then create value added flows smoothly along the value stream process, while Six Sigma approach will reduce the variation in the value added (Gaspersz and Fontana, 2011:93).

Fig. 3: Key to Lean Six Sigma (Resource: George, 2004:8)

E. Waste Waste can be interpreted as non value added activities.

Waste must be eliminated so that the company system can run more efficiently. According to Taiichi Ohno, there are 7 types of waste that commonly found in a company (Gasperz and Fontana,2011:9).

There are seven types of waste: 1. Transportation 2. Inventories 3. Motions 4. Waiting/Delay 5. Over Production 6. Over Processing 7. Defect

F. Value Stream Mapping (VSM) Value stream mapping (VSM) is a method to describe the

flow of material and information. VSM is a mapping process that shows the detail of the material flow, operational parameters lead time, yield, uptime, frequency of delivery, number of man power, the size of the batch, the amount of inventory, setup time, process time, the efficiency of the overall process, etc.

There are some steps in VSM design process: 1. Determine the product or product family 2. Design current state mapping 3. Design future state mapping 4. Design the improvement plan

G. Plastic Injection Process Plastic injection process is a formation process of plastic

resins into a particular plastic shape following the pattern of the mold (molding). Principles of this process are heating plastic resins into the molten plastic, injecting the molten plastic into a mold that is cooled by water to harden, and then picking up the formed plastic part.

III. RESEARCH METHODOLOGY A. Conceptual Model

Fig. 4: The Research Conceptual Model


B. Systematic Problem Solving

Fig. 5: Systematic Problem Solving

IV. DATA PROCESSING A. Standard Time Calculation

Cycle time data for each process is collected using stopwatch method and the results are examined using normality test and uniformity test. After the collected cycle times are stated as valid, the cycle time data for each process is added with performance rating and allowance so the standard time is obtained. The standard time of each process is needed to determine the appropriate time for operators to completing their works normally within the best working system. The test results of normality and uniformity data from each measurement cycle time of each process can be seen in attachment B of final project.

TABLE II

Standard Time Calculation

B. Current State Value Stream Mapping (VSM) Current state VSM of FB 7084 in PT.X, which is used to

map the existing value stream occurs during the production, can be seen on Figure IV.8 of the final project. According to the current state VSM, lead-time process for FB 7084 is 5,130.45 second with 37.5% delay activities, and 2.74% transportation activities, while value added time of the process is 3,071.65 second (57.89 %).

C. Waste Identification Waste identification during the production process of

FB7084 is done using waste checklist tool. The identification result can be seen on Table IV.9 of the final project. The result shows that waiting is the dominant waste during the production process, so that the research will be focused on minimizing waiting waste.

Waiting activities during the production process of FB 7084 can be seen below:

1. Waiting process of raw material in the mixing area 2. Waiting process of WIP material around the heating

area 3. Waiting process of FB 7084 product in the finishing

area

V. DATA ANALYSIS

A. Improvement Design The root causes of waiting waste, which is found during the

waste identification process, is identified using 5 whys method. The questions that occurs due to the use of 5 whys method is answered through observation and discussion with the companies. Once the root cause is identified, then improvement proposal is designed to address it. From the developed alternatives for each root cause, the best one is chose using scoring method. The developing and choosing process of the alternatives for each root cause can be seen on chapter V.2 of the final project.


The improvements design proposed is listed as follows: 1. Replace existing common sacks for raw material with

roped sacks that have core stopper so the sealing process will became easier and faster (In the existing condition, the sacks are sealed by sewing method).

Fig. 6: Core stopper

2. Design a pull system, from mixing to heating area, with production cards and a mixing request board to reduce stacking WIP material around the heating area. For detail information of the designed pull system with cards and a mixing request board can be seen on chapter V.2.2.1 of the final report.

Fig. 7: Production Card

Fig. 8: Mixing Request Board

3. Use the counting scale to measure product batch so the counting process will became faster and the amount of waiting product in finishing area will decrease.

Fig. 9: Counting Scale

B. Future State VSM The application results of the proposed improvement are

mapped into a future state VSM of product FB 7084 which can be seen on figure V.17 of the final project. Based on the future state VSM that has been made, it is known that lead-time of the process is reduced became 3,259.44 second from the origin is 5,130.45 second.

C. Comparative Analysis of the Current State and Future state

Once the future state VSM have been defined, the comparison is done between the lead-time in the current state with the lead-time in the future state.

TABLE III

Comparison Between Lead Times in Current State and Future State

TABLE IV

Activity Percentages Based on VSM

According to table III and table IV, lead-time process in the

future state can be reduced about 1871.01 second by minimizing and eliminating dominant waste so the delay time (waiting time) during the process is reduced from 1916.47


second to 171.80 second and the non value added activity time can be reduced from 140.7 second to 14.36 second.

VI. CONCLUSIONS AND RECOMMENDATIONS

A. Conclusions The research results can be concluded as follows:

1. Based on the identification results using the current state VSM and waste checklist, dominant wastes that occur in the production of FB 7084 is waste waiting. Total priority value of waste waiting on waste checklist is 9 and delay percentage is 37.35% from the lead-time process. Current state lead time process is 5130.45 second consisted of 0.11% WIP material waiting in mixing area, 10.05% waiting in heating area, and 27.20% waiting in the finishing and batch measurement area. While the other processes in current state are transportation by 0.03%, non-value added operations by 2.74%, and the value added activity by 59.87% from the lead-time process.

2. There are three-improvement proposal submitted to eliminate dominant waste in order to reduce lead-time process, listed below: a. Replacement temporary sealing method from

sewing to sealing with rope that has a core stopper

b. Application of the pull system on the mixing process scheduling with cards and mixing board tools.

c. Replacement of batch measurement method from manual to use counting scale

3. Implementation of the proposed improvements, can reduce the lead-time process became 3259.44 seconds, consisted of 5.27% delay activities, 0.05% transportation activities, 94.24% value-added operations, and 0.44% non-value added operations.

B. Suggestion Suggestion for PT. X:

1. The company should give more attention and support to continuous improvement process with 5S that have been implemented by the company.

2. The company should undertake the implementation of the proposed improvement.

3. The company should undertake trial and error process

before implementing the proposed improvements, so that the implementation process can run efficiently

Suggestion for further studies:

1. In further studies, further researches about lean six sigma are should be conducted in the entire production floor at PT. X.

2. In further studies, cost and other aspects are should be considered to get better improvement strategies.

3. Further studies can be done to eliminate other

waste during the production process of FB 7084.

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Jurnal TA Lean SIx Sigma

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