IMPLEMENTATION OF HEIJUNKA FOR IMPROVING PERFORMANCE

INDICATORS: A PROCESS SECTOR CASE STUDY

*K.S.Raguram, Ph.D Scholar, Sri Ramakrishna College of Arts & Science, Coimbatore-641006

**Dr.G Jayanthi, Research Supervisor, Department of Management Science, Sri Ramakrishna College of Arts & Science,

Coimbatore-641006

Abstract

This article presents the impact of implementing Heijunka, a Lean manufacturing tool in improving the productivity of an Injection moulding industry. Lean manufacturing is a business excellence strategy for continuous improvement in areas of Productivity, Competitiveness, Quality and Customer satisfaction. Heijunka, a lean tool is aimed at smoothing the production and subsequently creating the opportunities to improve manufacturing environment. Heijunka when applied, prepares the industries to face the demand about to generate in the near future. The study reveals that the results of Heijunka were quite substantial in terms of improvement in quality, productivity and customer satisfaction. By implementing Heijunka, we can stop producing work in batches and start processing orders according to the customer demand. Thus based on a process sector case study approach, proposed method was applied as well empirical data were analysed. Results were measured before and after the implementation by performance indicators such as, Cost of inventory, Speed (Lead time), Mix flexibility (monthly set up operations)and reliability level. Evidences prove that there is improvements in operational efficiency as expected.

Key words:

Lean manufacturing, Heijunka, Change over, Heijunka Box, Productivity, Quality, Customer satisfaction.

I. INTRODUCTION Heijunka is a Japanese word for conveying the meaning of leveling. It is a part of lean methodology of process improvement that helps organizations match unpredictable customer demand patterns and eliminate manufacturing waste by leveling the type and quantity of production output over a fixed period of time Heijunka is defined as “The distribution of production volume and mix evenly over time. Heijunka converts uneven Customer Pull into even and predictable manufacturing process. Heijunka is generally used in combination with other key Lean principles to stabilize value flow and this is a core concept that helps bring stability to a manufacturing process The requirement of implementing Heijunka arises in two situations namely, Product leveling and Production leveling. In Product leveling, large batches of the same product may reduce set-up times and changeovers, but usually result in:

Long lead times Swelling inventories Greater opportunities for defects Excessive idle time and / or overtime

An even Mix of products is critical to avoid these impacts Production leveling is a kind of cyclic scheduling that creates production regularity and coordination simplicity. In Production leveling, unevenness in the production complicates the production schedules.

Fluctuations in demand ( Boller or “Bullwhip” Effect) are often highly amplified and delayed throughout the supply chain.

Responding to fluctuating customer demand can result in increased overtime or idle time. Variable production schedules can be stressful = Unhappy workers.

A more level production volume eases these complications 1.1 Key elements of Level scheduling :

Production units are stratified according to planned sales volume

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The production sequence combines both orders (High Mix Low Volume (HMLV)) and Customer Forecast (High Volume Low Mix(HVLM)).

Sequence is designed to achieve the combined TAKT time for all items Eliminating production rate variance is required to achieve TAKT time Build only high volume products (top 80%) to Finished Goods (FG) supermarket, if orders are not available Lower volume items are NOT sequenced without firm orders Hold components in Raw Materials supermarket only for low volume items. Fill orders first from FG, second WIP, & third sequence them.

1.2 Background of the study : Every company is working towards achieving the customer satisfaction goal as set by their customers. Quality, Cost and On time delivery are the three main elements to achieve customer satisfaction. In order to achieve all these three elements, as a supplier, every one should have the Flexibility and stability in their production. Achieving flexibility in production with varying demands for the product is very difficult and concept of Heijunka can be used here for fulfilling this need. For a process to run smoothly and consistently with many forms of output, it's to average, not just in volume, but also in kinds. In a continuous flow manufacturing companies like in automotive industries, implementing Heijunka concept will be somehow done already in various companies like Toyota, Ford, etc. But adopting this concept in Batch processing industries will be very difficult due to the nature of business and sequence of processes involved. This article gives the input on various ways of implementing Heijunka concept in Batch processing industries like Plastic Injection moulding industries. In these industries, there are a number of competitive and substitutive products on the market, the demand for specific products often exhibits a much higher volatility than in the past. Therefore, the manufacturing companies, when creating production plans or schedules, must focus on the fact that plans in case of a drop in demand for one product and a growth in demand for another product enable to achieve the necessary quantities of production volume while there is no overproduction of products without in advance known expected sales of products. It is significant that HEIJUNKA, a Lean management tool which contribute to this approach significantly. The approach towards this article is conceptual to find the need for implementing Heijunka in production process. The systematic approach of reveiew of literature will give more insights for implementing this model. It is a descriptive study based on the problems faced by the select case and there is a need for studying the significance of implementing a strategy for reducing the time with product leveling. 1.3 Profile of the Industry : For batch processing industry to test the performance, Plastic Injection moulding company is taken for analysis. There are various plastic items which are used in day to day life like, Automobiles, Aerospace, Medical industry, Home appliances, etc.. Plastic components are being used in most of the industries in one or the other form. The following image shows the Plastic component Manufacturing process adopted by the select manufacturing sector.

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(developed for the research purpose)

Procurement of as raw materials (Granules and other items like screws as bought out items Mixing ( colour granules with master batches to get variety of colors ) Pre Heating ( removes moisture from granules to before loading into hopper wherever required Moulding process ( with the help of Core and Cavity with the heating to required temperatures as per

granules type) Removal of product (from the machine and kept for cooling to room temperature ) Deflashing activities ( to remove flashes from the product) Assembling of two or more parts based on product type Final inspection (for visual defects) & Packing of products as per customer requirement

In this paper, we will focus on the implementation of Heijunka system in Plastic Injection moulding companies to improve the business performance. Researchers and practitioners can evaluate general applicability of this method by applying it in different companies that share similarities related to batch processing operations. 1.4 Area of study : In this paper, plastic injection moulding components manufacturers were considered for implementing the concept of HEIJUNKA and the extent to which these manufacturers have implemented this concept is analysed. Based on that, the best practices followed by manufacturers can be shared to others to have a better performance in other manufacturing companies. In general, HEIJUNKA is not popular because of various factors including technical and social factors. When implemented with the long term goal, HEIJUNKA will yield good results in the business performances (performance indicators) of achieving, Good Quality Low Cost On time delivery

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This paper will analyse the possibilities to provide the customers exactly what they need and when they need it. Also the inventory level of the components to be maintained as low as possible to see that the money is not held up in raw materials, Work in progress and finished goods. This can be achieved by level loading the customer order fluctuations and by reducing the change over time between model to model since the efficiency of change over is the FULCRUM of HEIJUNKA. 1.5 Objectives of the study : The main objective of the study are as follows :

a. To understand the extent of implementation of HEIJUNKA box concept in injection moulding manufacturing.

b. To ascertain the requirement of implementing HEIJUNKA box concept and offer best practices followed in Plastic Injection moulding industries.

Based on the objectives of this paper, the following techniques were considered for the purpose of finding the results on Heijunka implementation for required efficiency :

a. Data collection on various products for various customers b. Present method of communication of production scheduling (Present state) c. Gap analysis for identifying improvements (Future state) d. Improvement opportunities to implement HEIJUNKA Box

1.6 Scope of study : Plastic injection component manufacturer from Coimbatore area are considered for the analysis where they have various range of molding machines starting from 50 tons to 350 tons. Machines will produce variety of components depending on the mould size and the component construction. In order to study the implementation of Heijunka model, data collected for 105 shifts for the complete production capacity and only the injection moulding machine highest number of parts produced for a given period is considered. Collected data was analysed with simple statistical tools and findings were discussed for further improvement.

II. REVIEW OF LITERATURE Luciano Fonseca de Araujo and Abelardo Alves de Queiroz (2010) have presented an implementation model based on production leveling designed to batch production.They have designed the methodological approach by using a guideline for case study and comprises with Present state and future state. They also presented a simple and new method for production leveling which was empirically tested.

Milan Fekete and Jaroslav Hulvej (2015) have presented a paper on Production planning and production leveling of a manufacturing company and how production planning which is a sub system for production system works and what are the different tasks which must be accomplished so that the production planning works effectively not only within manufacturing company itself and also in relations with sullpiers and mainly with customers.

Huttmeir et al. (2009) tried to find a trade-off between heijunka and the just-in-sequence method. They analyzed whether it would be better for a manufacturing plant to use heijunka to maximize leanness, or use JIS to maximize its responsiveness. Their work indicates that the answer may lie somewhere in the middle, with heijunka used to smooth out the most extreme production values with the remainder of production carried out with JIS. It is important to understand this trade-off, as it gives essential insights into the bigger picture of trading-off between leanness and agility

Judith Matzka · Maria Di Mascolo · Kai Furmans (2009) has analysed a kanban controlled and heijunka leveled production system where the arriving demands are controlled and limited by a kanban loop. They have modeled the production system as a queueing network with synchronization stations with the aim of determining the optimal number of production kanbans, and thus the buffer size that guarantees a given service level. Heijunka is a key-element of the Toyota production system which levels the release of production kanbans in order to achieve an even production flow over all possible types of products, thus, e.g. reducing the bullwhip effect.

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III. CONCEPTUAL BACKGROUND OF USING HEIJUNKA BOX Definition of Heijunka Box :

o A Heijunka box is a visual scheduling tool used in Heijunka, a concept originally created by Toyota for achieving a smoother production flow.

o While Heijunka is the smoothing of production, the Heijunka box is the name of a specific tool used in achieving the aims of Heijunka.

o The Heijunka box is generally a wall schedule which is divided into a grid of boxes or a set of 'pigeon-holes'/rectangular receptacles.

o Each column of boxes representing a specific period of time, lines are drawn down the schedule/grid to visually break the schedule into columns of individual shifts or days or weeks.

o Coloured cards representing individual jobs (referred to as KANBAN cards) are placed on the Heijunka box to provide a visual representation of the upcoming production runs.

o The heijunka box makes it easy to see what type of jobs are queued for production and for when they are scheduled.

o Workers on the process remove the kanban cards for the current period from the box in order to know what to do.

o These cards will be passed to another section when they process the related job.

The Heijunka Box in Visual Management o The advantage of a heijunka box is in the way it displays production processes and the relationships between

component and product production. o This provides a means for visually managing the flow of production for evenness and flexibility. o Eliminating dramatic fluctuations in production will make the entire process more predictable and

manageable, as well as maintaining just-in-time delivery of needed materials, and minimizing inventories. o Waiting time is eliminated and the potential for overproduction is reduced. o The overall objective of heijunka is to match production to customer demand, while at the same time using

production resources in the most efficient manner possible. o The result is a smooth and predictable flow of production. However, customer demand is not always smooth

and predictable. o Managing production through the heijunka box offers a system for immediately responding to changes in

demand, but it requires a workforce that is versatile and capable of handling a number of tasks. o The workforce, equipment, and transportation systems must be flexible enough to handle a number of

production and delivery requirements.

III RESEARCH METHODOLOGY : Design, Methodology and Approach 3.1 Data collection :

The molding company is primarily producing the plastic Injection moulding parts to their various customers (Both Internal & External).

More than 350 variety of parts are being produced in the moulding machines ranging from 10g to 750 g. The type of demand is mix of Low volume and High mix (LVHM) products and also high volume Low Mix

(HVLM)Both Internal and External customers are sending the purchase orders to Plastic Injection moulding company in different timings (i.e, Daily, Weekly 7 Monthly).

3.2 Present method of communication of production scheduling (Present state) :

Internet source : Lean.org

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All the purchase orders received from customers are compiled manually by production planning executive and informed to relevant teams through hard copy for their further processing.

No visual management system applied for the production planning information. Heijunka Box will help the production personnel and tool preparation personnel to plan for the products

depending on the daily plan and customer requirement.. 3.3. Gap analysis :

One of the gap observed in the present method of communicating the schedule is there is NO visual management system followed which may lead to delay in preparing the tool for further production.

Supervisors may not be able to visualize the next requirement since all the planning details are shared in hard copy form.

With the above input, importance of Heijunka Box is discussed with the production and tool crib persons concerned and necessary actions taken to design the Heijunka box for this production process.

IV. DATA ANALYSIS AND INTERPETATION :

Data collection methodology defined to analyse the requirement of Heijunka box and it was decided to collect data for the production planning for 105 shifts from the company and the way in which the production planning is happening physically. Based on the discussion with the executive of product planning of the moulding company, the data has been collected for 105 shifts containing the following information in an excel sheet.

1. Machine name 2. Shift 3. Description of part 4. Part number 5. Component weight 6. Number of cavities in a mould 7. Shot weight 8. Cycle time in Secs 9. Plan hours 10. Number of shots / shift 11. Number of components 12. Material to be used 13. Colour of the material 14. Raw material requirement details 15. Alternate plan for any contingency 16. Mould status like Regular or Critical

The following are the observations considered for analysis. 4.1 Daily production and material plan data were analysed for the collected shifts for findings As explained in section III, Heijunka box will help to implement Visual Management for the production scheduling. 4.2 In order to design the Heijunka Box, data collected was analysed with simple statistical tools and no. of various parts produced in the machines were taken for the given period. 4.3 The number of parts produced in each machine for the given period is compiled and produced in graphical manner below.

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(Graph No.1 ) Primary Data

From the above graph No. 1 , it is clear that the 350T I was used for producing more variety of parts. In the same way, one more data was also collected to see which machine was frequently used for producing the parts in a given period and the data is depicted in the below graph.

(Graph No. 2 ) Primary data

Based on the graph above (No.2), it is understood that machine 350T I was used in more no. of shifts. Hence, it is decided to introduce Heijunka Box concept in 350 T I machine and based on the feedback from the production and tool crib personnel, this concept will be horizontally deployed to other machines. Design of Heijunka Box for 350 T I machine. With the details of products planned for 350T I machine, the Heijunka box was designed as provided below.

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Based on the monthly and weekly plan, the Heijunka box will be updated for a whole week. Depending upon the products planned for production. Following departments will prepare their activities. Stores : Stores will plan to issue the raw material in advance with this Heijunka box. KANBAN cards will be hanged on the relevant boxes and stores personnel can pick the card and issue the items accordingly. Tool Crib : Tool crib team will prepare the moulding tool in advance based on the timings mentioned and keep the tools ready for change over. Change over is the fulcrum of implementing Heijunka concept. When change over time increases, production line doesn’t have the flexibility in production which will delay the output and ultimately the customer satisfaction. Hence, tool preparation as an external activity plays a vital role in achieving the change over. Production : Production team will ensure the availability of necessary raw materials, moulding tools and required manpower for running the parts planned at that particular time. V.FINDINGS & CONCLUSION With the above mentioned improvements for converting the Internal activities into External activities, tool change over time has been reduced considerably which helps to bring out flexibility in the production. On implementation of this new way of change over, availability of machine was increased which helped to increase the Overall Equipment Effectiveness (OEE) of the machine. The average OEE of M1 was around 71% before which has increased to 84 % after the implementation of these improvements. All these improvements can be horizontally deployed to all machines available in the plant and required minor modifications can be done based on the type and positioning of the machine in the plant. Implementation of concept of heijunka will result in improved overall productivity and elimination of waste, cost-effective production and delivery of only the necessary quantity of products at right quality, at the right time and place, while using a minimum amount of facilities, equipment, materials and human resources which will results in reduced inventory levels in addition to human efforts and time. In every industry safety is a significant factor which covers by less inventory and single flow method. The production is levelled by implementing the concept of heijunka. REFERENCES

1. Paulina Rewers, Adam Hamrol. Production Leveling as an Effective Method for Production Flow Control – Experience of Polish Enterprises, Procedia Engineering, Volume 182, 2017, Pages 619-626 https://doi.org/10.1016/j.proeng.2017.03.167

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2. Akshay M. Ramekar et al., International Advanced Research Journal in Science, Engineering and Technology AGNI-PANKH 16 Jawaharlal Darda Institute of Engineering and Technology, Yavatmal Vol. 4, Special Issue 3, January 2017(IARJSET ISSN (Online) 2393-8021 ISSN (Print) 2394-1588)

3. Luciano Fonseca de Araujo and Abelardo Alves de Queiroz. Production Leveling (Heijunka) Implementation in a Batch Production System: A Case Study Federal University of Santa Catarina, Department of Manufacturing, GETEQ Research Group, Caixa Postal 476, Campus Universitário, Trindade, 88040-900, Florianópolis, SC, Brazil. lfaraujo2005@gmail.com, abelardo@emc.ufsc.br

4. Judith Matzka · Maria Di Mascolo · Kai Furmans. Buffer sizing of a Heijunka Kanban system. J Intell Manuf (2012) 23:49–60 DOI 10.1007/s10845-009-0317-3

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