Manufacturing Enhancement through Reduction of Cycle Time using Different Lean Techniques

In recent manufacturing system the most important parameters in production line are work in process, TAKT time and line balancing. In this article lean tools and techniques were implemented to reduce the cycle time. The aim is to enhance the productivity of the water pump pipe by identifying the bottleneck stations and non value added activities. From the initial time study the bottleneck processes were identified and then necessary expanding processes were also identified for the bottleneck process. Subsequently the improvement actions have been established and implemented using different lean tools like value stream mapping, 5S and line balancing. The current state value stream mapping was developed to describe the existing status and to identify various problem areas. 5S was used to implement the steps to reduce the process cycle time and unnecessary movements of man and material. The improvement activities were implemented with required suggested and the future state value stream mapping was developed. From the results it was concluded that the total cycle time was reduced about 290.41 seconds and the customer demand has been increased about 760 units.


INTRODUCTION
Nowadays, manufacturing industries utilize more resources toimprove their productivity. It is very important to stabilize their resources allocation and work environment. They wantto use tools to optimize its processes to attain good results to meet the demand.They focused only on production with higher efficiency inless cycle time but they mustfocus mainly on customersatisfaction. In order to compensate increase in competitiveenvironment, many manufacturing industries are looking for awinning in their competition. Manufacturers have tounderstandthe conventional production system and it hasto connect with the lean tools and techniques.Value Stream Mapping (VSM) lean tool is a technique that brings allprocessing steps at one place and is used to draw attention ofdifferent wastes and eliminates them in future state map.TAKT time is the rate with which products flow through theline of production, it can be achieved by synchronizing theproduction rate to the rate of product demand. As soon as manufacturers focused on processes, they found waste associated with changeovers, process control factory layout, and so they tried to find ways to reduce or eliminate waste. The idea of lean concept is to maximize the customer value and minimize the wastes to increase the cost of products. A case study was carried out in a water pump pipe manufacturing industry located at Chennai, a producer of various models of water pipes. This study focused on the manufacturing area, where the chamber produces suction and delivery pipes for the water pump. This study was carried out on VSM, 5S, Kaizen and line balancing in the manufacturing area. The manufacturing chamber requires a standard work procedure to be displayed in the machining area which decreases cycle time. Line balancing was done for balancing the workload between the workers which could reduce the idle time.

LITERATURE REVIEW
Lean manufacturing is a performance based process used in manufacturing industries to increase profit and competitiveness through eliminating waste, reducing the cycle time and decreasing the component cost [1], [2]. The basics of lean manufacturing and VSM employ continuous improvement processes to focus on the elimination of the seven wastes or non value added activities within the industries. It is basically a workplace management methodology, which helps to improve the working environment, human capabilities and thereby increasing the productivity [3]- [5]. Nallusamy et al. discussed about the development of activities that maximize the overall effectivenessof equipment, processes and plants through uncompromisingelimination of losses [6]. Teams were made from every level oforganization, managers, engineers, staff, technicians, lineworkers. The principal behind is that a large number of smallimprovements are important than a few improvement of largevalue.VSM is often used in process cycle time improvement projects since it demonstrates exactly how a process operates with detailed timing of step-by-step activities [7]. It is used as a main tool to identify and implement the opportunities for various lean techniques. Various research articles have discussed the different applications of VSM method in different production areas [8]- [10]. VSM is used to define and analyze the current state for a product value stream and design a future state focused on reducing waste, improving lead time and improving workflow.A value stream map provides a blueprint for implementing lean manufacturing concepts by illustrating how the flow of information and materials should operate. VSM is divided into two components as big picture mapping and detailed mapping [11]. Cycle time or lead time is nothing but the time between the release of an order from the customer and the time taken for receiving the finished product by the customer. A study was carried out for each machineoperation by using the techniques of method study and timestudy which are related to the subject of industrialengineering where each part involved inmachining process like job setting time, tool setting time,CNC program loading time, program running time,speeds, feeds, depth of cuts used for the every operation, toollife, tool changing time, job unloading time etc [12]. Work standardization in various production industries leads to reduction in their lead time, cycle time and setup time and also increase the rate of quality of the product [13], [14]. Through a case study the various defects in a cast iron manufacturing industry were inspected and the required suggestions were given to remove the defects. [15], [16].
Similarly the applications of VSM and line balancing in an automobile component manufacturing industry reduces the setup time and cycle time and the case study was helped to balance the work load between the workers by eliminating idle time [17], [18]. A lean tool of Kaizen was implemented in a daily process to reduce the movement distance and time of the workers, who was moving every timefor searching tools and materials. This was implemented for the purpose of productivity improvement to meet the customer demand in time [19].Pandit et al found that with the help of line balancing it was possible to improve productivity and achieve better utilization of resources [20]. The less attention on accuracy of standard time and poor work arrangement were identified as the root cause for low efficiency and increase in layout utilization by changing the position of equipment or by introducing the new machine into the layout. Line balancing is the appropriate method to overcome the above root cause and to enhance the productivity [21].Thecycle time of each process of existing system was calculated and proposed a new line balancing method to reduce non-value added(NVA) activities, eliminate waste and reallocate work [22].Reduction of cycle time using lean tools in an automobile manufacturing industrythrough the existing processesstudy found out NVA activities and reduced the same using lean tools whichresulted in shortening of cycle time to avoid delay between workstations [23]. In this, the standard process chart and spaghetti diagramwere used to analyze the operator movement.A case study was reported on application of VSM in an automobileindustry where they improvedtheir productivity by reduction of cycle time through improvement in value adding activities [24].Based on the above literature an analysis was carried out in a pipe manufacturing industry to improve their productivity using different lean tools.

METHODOLOGY
The existing manufacturing process of selected water pump pipe was studied to identify the bottle necks. After the processes were studied, the existing cycle time and the value and NVA time for each process in themanufacturing line time were calculated using time study method. Lean tools such as VSM, 5S and line balancing were used to identify the value and NVA activities.Improvement activities was planned and implemented to reducethe total cycle time and process time. The proposed layoutwas developed after the line balancing was established and the future state VSM was also developed. Finally the observed results were compared with the existing values. The methodology flow chart for this study is shown in the following Fig. 1.

Process Flow for Water Pump Pipe
The rolled sheet materialof stainless steel 304 with 342 mm height was initially cut by the sheet cuttingmachine and the sheet was subjected to bending process slightly toinitiate for rolling process. The sheet was rolledin the sheet rolling machine and sent for spot and run weldingfollowed by tinkering process.After expanding process was carried out the water pumppipe was edge grinded using grinding machine followed byfacing operation. Later the slotting was performed with slotson four sides of the water pipe and the outer ring was spot weldedfollowed by outer ring facing.Then the total length of the water pump pipe wascorrected followed by inner ring tack welding. The innerring spot welding and facing operations werecarried out. Finally the inner ring was fully welded and the innerand outer ring welding area was grinded followed by the innerand outer ring expanding operations.After the machining operations were done in the previousstations, the water pump pipe was checked for thediameter with the gauges. Later the required size was attained,the pipe was moved to burr cleaning followed by emery andbuffing. Finally the water pipe was inspected andpackaged. The process flow is shown in the Fig. 2.

Current State Value Stream Mapping
Based on the existing data the current state VSM was developed to know the existing process steps and to find out the value and NVA activities is shown in Fig. 3. The total cycle time,value and NVA processes time were also calculated for developing the future state VSM.

Calculation of Workers Movement
The present layout of production line is shown in Fig. 4. It indicates the movement of workersand materials from raw material inventory to the finished product. It was observed that the total movement of the workers during the manufacturing of water pump pipe is about 115 meters.

5S Implementation
The different wastes were identified around the manufacturing area to be eliminated through various improvement processes. One among the processes 5S was implemented in order to reduce the waste of waiting andmotion as items are easier to find in the first stage. The second stage of 5Simplementation results in ensuring that components, equipment, tools,machines, workers are

Reduction of Process Flow Time
In the water pumppipe manufacturing process materialhandling takes more time.Especially during the edge grinding, welding and tinkeringprocess more time was taken to handle the materials and hence the process flow time increased. To reduce the process flow time a new material handling stand was designed and proposed inorder to reduce the NVA time.After implementing 5S and new material handling device there was reduction inflow time and the material handling time was eliminated,which ultimately reducedeach process time.It was found that the flow time of the pipe before implementationof the above was 1048.06 seconds.After implementation it was reduced to 969.12 minutes.The total cycletime was reduced nearly78.94 seconds and there was an improvement of 9.2% reduction in total flow time.In the existing system there was a manual setup for fixing the pipe in the machine.The proximity sensor was used to control the hydraulic cylinder movement and there was no physical contact.During the process the piston was not able to return to its original position due to sensor problem and it leads to breakdown.To avoid this problem there are three best alternatives, introductionof limit switch, solenoid valve and electro mechanical actuator were reducedthe process time. The method used was evaluation matrix whichcan be best for finding the best alternative with theircorresponding parameters.Alternative-I is limit switch, alternative-II is solenoid valve and alternative-III is electro mechanical actuator. The parameters for the alternatives given with key letters like speed, maintenance, reliability and performance are A, B, C and D respectively.The quantitative method matrix is given in Table I and the decision matrix for selected alternatives is given in the Table II.  From the decision matrix, it has been clearly observed thatalternative method Iof limit switch was ranked as 1 with the total points of 417.71.Hence the design was proposed withalternative method I of limit switch.After implementing the proposed design, the cycle time ofthe expanding process was reduced to 211.47 seconds.The flow time of the water pump pipe before implementationof decision matrix was 969.12 seconds.After implementation of all the lean tools it was reduced to 757.65 seconds.The total cycle time was reduced about 290.41 seconds after implementation of different lean tools which is about 28% in the overall cycle time.

Line Balancing
Line balancing is the process of assigning tasks todifferent workstations, so that all the workstations have approximately equaltime requirements. We usedthe method of line balancing to-minimize idletime-balance bottlenecks.Based on the current line balancing layout, the new layout was proposed with some of the processes were merged intosingle station likeM1with M2, M3withM4, M5withM6, M9 withM10, M17 with M18, PIwith M21 and F2 with P. The proposedline balancing layout is shown in Fig. 6. After implementing the proposed line balancing it was found that the movement distance of the workers in the manufacturing area was reduced to 104.2 meters through merging the different workstations. Ultimately, the lead time was also reduced by the proposed line balancing method.

Future State Value Stream Mapping
Based on the data collection and analysis the future state VSM was constructed by combining different processes to reduce the cycle time and is shown in Fig. 7. From the future state VSM it was found that the total cycle time was reduced by 27% and NVA time was also reduced.

CONCLUSION
The developments were established in the selected manufacturing line of water pump pipe through the analyses of existing scenario.Based on the calculated results the following conclusions were made.
From the current state VSM, it was clearlyidentified the value added and the non-value added time for each process. The cycle time was reduced by identifying and eliminating wastes through 5S implementation. Expanding process has more non valueadded activity as compared to other processes after theimprovement activity implementation. The movement distance was reduced about 10.8 meters through the implementation of proposed line balancing. It was clearlyobserved from the future state VSM that thetotal cycle time was reduced 290.41 seconds and monthlydemand was increased as 4320 units instead of 3560 units per month which is increased by about 18%.