APPLYING SIX SIGMA METHODOLOGY IN A BRICK KILN INDUSTRY THEREBY REDUCING DEFECT LEVEL

Transcription

1 APPLYING SIX SIGMA METHODOLOGY IN A BRICK KILN INDUSTRY THEREBY REDUCING DEFECT LEVEL Akhil Khajuria 1, Kapil Singh 1, Khalid Sheikh 1 and Navdeep Malhotra 2 1 Student, M.Tech (M&A) SME, Shri Mata Vaishno Devi University, (J&K), India 2 Professor (Mech Engg.) YMCA University of Science & Technology, Sec-6, Faridabad, Haryana,India akhil.khajuria@yahoo.com Abstract: The fundamentals of brick manufacturing have not changed over time. However, technological advancements have made contemporary brick plants substantially more efficient and have improved the overall quality of the products. A more complete knowledge of raw materials and their properties, better control of firing, improved kiln designs and more advanced mechanization have all contributed to advancing the brick industry.. Since the repetitive production of bricks meeting standards is very demanding in the industry, the implementation of cyclic control on the brick kiln set-up has naturally become an important objective for researchers. In this paper, a similar kind of work has been presented with the objective of reducing the no. of defects that were caused due to various reasons in a Brick Kiln set up.the purpose of this research is to study quality related problems while producing building product and to improve the quality of the product using Six Sigma methodologies in a Brick Kiln Industry. This research paper aims at using a case study approach to show how Six Sigma methodologies can be used in order to improve the quality of Bricks in a Kiln. The variables which were affecting the production quality were sorted out and consistently the defect level was reduced by using DMAIC principle of six sigma implementation on the manufacturing set up after formulating the problem. Keywords: De-Hacking, forming, firing, CTQ (characteristics Critical to Quality), DMAIC, Schimdt and Launsby formula. 1.0 Introduction In today's competitive world, an organization's success is based on its ability to produce the products and services faster, superior and cheaper than their competitors. Global competition and demand from the customer for high quality andlow cost product is forcing the organizations to search for the means to improve their products and processes. Six Sigma is a well-known concept for improving quality and productivity.six Sigma is a structured and disciplined process, focused on delivering perfect product or services to the customer consistently [1]. In statistical terms, Six Sigma means 3.4 defects per million opportunities (DPMO). It is a methodology that emphasizes Define, Measure, Analyze, Improve & Control (DMAIC) approach to problem solving [2].The aim of Six Sigma methodology is to integrate all operations throughout the processes to make them produce their desired results. It can be implemented in various processes related to manufacturing and services including health care, information technology, distribution operations, warehouse and inventory management, supply chainmanagement and manufacturing.this work aims at improving the quality of a product in ABC Brick Kiln industry using Six Sigma DMAIC methodology. 1.1 Statement of the Problem ABC Brick iln industry analyses a quality complaint in its product from customer. The company was required to improve the quality of the product for its customer satisfaction. 1.2 Purpose of the Work The purpose of the work is to study quality related problems in thermoformed plastic products and improve quality of the product using Six Sigma DMAIC Methodology. 1.3 Objectives of the Work 1. To study and determine quality problems in the Industry. 2 To identify commonly used Six Sigma tools and techniques. 3 To solve the quality related problem and increase quality of the product using Six Sigma DMAIC methodology. 917

2 1.4 Assumptions of the Work 1. The data provided by the industry are precise. 2. The data collection process adopted by the industry is reliable. 2.0 case study Although the basic principles of manufacturing are fairly uniform, individual manufacturing plants tailor their production to fit their particular raw materials and operation. Essentially, brick are produced by mixing ground clay with water, forming the clay into the desired shape, and drying and firing. In developed countries, all molding is performed by brick-making machines. However in India half of the Brick kilns still use the conventional method of molding. Even in this brick kiln manual method (using cope and drag) is used for molding bricks. Figure 2. Systematic Representation of Brick Manufacturing Process Table 1 proposes the specifications of the process. Material Used Operating Temperature Production Rate/hr Manufacturing time Fuel Materials Used Table 1. Process Specifications Brick Cakes from the mixture of Clay, Soil and Water 204 o C(final drying) Units per hour 10hrs (with a break of 1 hr) Coal + Coaltar + Wood 2.0 Application of six sigma DMAIC methodology 3.1 Define phase In this stage, with the help of supplies, input, process and output various stages in the rings process were identified. The results of the Define stage are as follows: 1. Customer Workers who are involved in the process of De-Hacking. 2. Team Project Team involves all those who are involved in the process of Preparation, Forming, Drying, Hacking and finally firing. 3. Process Boundaries All Process Steps from putting the raw materials till the final Bricks are obtained All set-ups have preventive maintenance schedules in addition to random breakdowns.all work is inspected before moving to the next operation in order to eliminate additional rework steps.setups are required at each step in the process whenever the previous and current product types differ. 918

3 3.2 Measure phase In this stage, the characteristics of the product or process to be measured are selected and the performance standards for those outputs are defined, and then a CTQ (characteristics Critical to Quality) Flowdown is performed to understand the relationship between the inputs and outputs. Figure 2. Manufacturing Cycle The diagram above shows how the primary CTQ manufacturing cycle is a function of parameters which are under control, such as machining times, setup and down times and crane availability. Other factors, such as product mix and holiday schedules are also be taken into account. The basic aim of this stage is to focus on improvement effort by gathering information on the current situation. This information include what is the current sigma level and how much can be expected to improve and how much time will be required to do so Current Sigma Level For this purpose data for the production of bricks was taken every day. Product yield was determined and number of defects in total to establish defect yield and sigma value. Fig. 3 Production v/s Defects below shows the number of bricks produced & number of defective bricks produced for the consecutive five days Calculations Defects/unit (DPU) = Figure 3. Production v/s Defects Defects per million opportunities (DPMO) [3] 919

4 = 1,000,000 = 1,000,000 = So, DPMO is Schimdt and Launsby formula [4] This formula is a basic formula for calculating the sigma level. It just needs the variable i.e. Defects per million opportunities i.e. DPMO. Sigma = Sqrt ( ln(dpmo)) = Analyze Phase Once all the measurements have been done it is the time to critically analyze the process, and to determine the key variables and also to determine the next step for the purpose of improvement. With the help of workers and engineers there and studies have determined the following factors that influence the product quality:- Proportion in which the various raw materials are mixed viz clay, soil, water Method of Drying and the time required for drying also plays a vital role Rough Handling of the Raw Bricks can also produce defects Brick kiln Design Method of Firing Proper placements of Raw Bricks in the firing chamber during Hacking Most of the bricks break during packing and transportation i.e packing and transportation losses Although the above factors were the key variables that effect the sigma value but it was practically impossible for us to measure the %age effect that each factor has on the production quality. So it was decided to prepare charts and analysis report on the no. of defects that are produced at each of the six stages mentioned before.results are shown in the following table. Table 2. Average defects and their effect Stage Average no. of defects on variation (per 1000) %age effect of each variable Mining & Storage 0 0 Preparation Forming the Brick Drying Firing & Cooling De-hacking Total This shows that the no. of Defects in drying stage is maximum followed by firing and cooling, forming, de-hacking and Preparation. We have almost zero defects in mining stage. So our improvements will be based on this analysis. 920

5 3.4 Improve Phase After the analysis and brainstorming in the previous step, now comes the Improvement stage. For this purpose a visit was taken up in another brick kiln located in the vicinity. Then the processes used in the kilns were compared. On the basis of this comparison, knowledge and understanding some improvements were proposed. Then these improvements were consulted with various expertise and the kiln owners. Here is the list of all the improvements that were made: Improvement List- 1 a) Improve Brick Drying Before Firing:-Extended drying time reduces fuel requirements, even drying throughout brick stacks reduces defective firing of bricks. b) Improve Air Circulation For Drying Purpose:-This can be done by using high speed fans. This will improve the quality of raw brick. c) Improve Air Flow Control In The Kiln:-Controlling the kiln opening size allows better control of air flow speed and direction to improve combustion. d) Stack Fuel Around Bricks To Facilitate Preheating:-Solid fuel is mixed with the bricks throughout the kiln, either as sawdust mixed into the brick mass or as fuel channels in different levels of the kiln. By doing this, a combustion zone can be generated in the kiln that gradually moves upwards, using the residual heat in the lower, already burnt bricks for preheating of combustion air. The residual heat in the flue gasses is used for drying and preheating of the higher levels of crude bricks. e) Switch To Propane Or Natural Gas Fuel:-If available and competitively priced, these fuels have significantly less emissions and can increase production quality and speed. f) Proper Placement Of Raw Bricks In The Furnace:-The setting pattern of the bricks has considerable influence on the defect level. The bricks should not be placed face to face or face to back instead they should be placed with some spacing in between. This will increase the brick area that is open to fire Improvement List- 2:- This is a list of those improvements which the kiln owners have considered infeasible and denied to apply due to financial constraints and lack of time. Here they are in brief:- a) New and Improved Kiln Design instead of using conventional kilns b) Stopping air leakages help in better control of air flow and also improve combustion c) Use of Robotic Arms in case of loading and unloading the bricks in Hacking and De- hacking processes reduces the manual effort and time. It can also reduce the defects that are caused in these stages. d) Transportation Losses if reduced will also contribute in reducing the total no. of defects. e) Use of Automatic Brick Molding Machine instead of using conventional manual molding methods using Drag and Cope will reduce the time taken considerably. Use of this machine can reduce all the defects that were produced in the Forming Stage. f) Improve the method of Firing will not only reduce the pollution caused by the kiln but also help in controlled Firing thereby reducing the defects. g) The proportion with which the raw materials specially water and clay are mixed. With the help of the Brick kiln Owner we finally these improvements were applied. The Defect level has came down. Reading was taken of the three furnace chambers Calculations Defects/unit (DPU) = = S.No. No. of Defects Total no. of parts produced Total Defects per million opportunities (DPMO) [3] 921

6 = 1,000,000 = 1,000,000 = So, DPMO is Schimdt and Launsby formula [4] Sigma = Sqrt ( ln(dpmo)) Capability= Sigma/3 So, Sigma = This clearly shows that defect level has come down and sigma level has improved. It is now Finally the success was achieved in reducing the defect level to such an extent. We could have achieved even more but that required changes in the whole processes, using high quality machines, automatic machines for clamping and packaging purpose. All these steps will decrease the manual effort and decrease the time taken thus improving the efficiency of the process. 3.5 Control phase The final step in this DMAIC project was to ensure that the proposed improvements should be applied in the manufacturing process of bricks. Further stress should be paid on other improvements as well particularly in the method of Firing. There is a need to understand that new methods can further be improved. Also we should summarize our key learning s and involve every worker in suggesting improvements. We should also develop a Monitoring System. Whenever, the inputs were determined to be out of bounds, immediate attention should be given to correct the situation and bring the process back under control. 4.0 Conclusion So finally the success was achieved in reducing the defect level and thereby improving the sigma value in. The final sigma value of 3.79 is achieved. However if industries want to retain or improve this sigma value, necessary control measures have to be taken and proper checks have to be imposed. Quality culture must be developed amongst employees and proper training must be given to them. A good decision for project generation not only provides profits but also increases customer satisfaction. This study aims to investigate the effect of applying six sigma tools in a Brick Kiln industry trying to decrease the scrap rate. This study has two advantages. First is to choose the best tools that fit that type of industry. Second is to encourage similar companions to apply the same methodology. 5.0 References 1. Linderman, K., Schroeder, R., Zaheer, S., Choo, A., (2003). Six Sigma: A goal-theoretic perspective, Journal of Operations Management, Vol. 21, No. 2, Mar., pp Pande, P., Neuman, R., Cavanaugh, R., (2000). The Six Sigma Way: How GE, Motorola, and Other Top Companies are Honing Their Performance, McGraw-Hill, New York. 3. Breyfogle, F. W. (2003), Implementing Six Sigma: Smarter Solutions Using Statistical Methods, Wiley. 4. Schmidt, S.R., and Launsby, R.G., Understanding Industrial Designed Experiments, 4 th ed., Air Academy Press, Colorado. 922