Preventive Maintenance and Root Cause Analysis of Soham Pre- Treatment Washing Machine in Axle Assembly Line

Transcription

1 Preventive Maintenance and Root Cause Analysis of Soham Pre- Treatment Washing Machine in Axle Assembly Line Naveen K.J 1, Dr. H.Yogish 2 1,2 Department of Mechanical Engg, SJCE, Mysuru Abstract-Root-cause identification for quality and productivity related problems are key issues for manufacturing processes.it has been a very challenging engineering problem particularly in a multistage manufacturing, where maximum number of processes and activities are performed. The maintenance function is a key area in which competitiveness through efficiencies and world-class performance can be attained by focusing on the prevention and reduction of long and costly equipment repair times. Every organization depends on the availability and efficiency of its resources for it to remain competitive in a very challenging economic climate. The proper functioning of its assets used in the production line is crucial for delivering a product on time and that meets the expectation of the customers. One of the ways to increase the productivity is to increase the availability of the existing machines. More the machine availability more is the scope for increase in the productivity. In this project, Preventive maintenance, root cause analysis, is adopted to improve the machine availability & production capacity, MTBF to certain extent and reduce the downtime and MTTR of the machine and finally to prevent the failure of equipment before it actually occurs. Thus this project aims to minimize downtime, maximize availability, Increase MTBF & decrease in MTTR. The project work concludes that this will help the maintenance department to increase the machine availability & production capacity. Finally suggestion was given for further work. Keywords: Preventive maintenance, Root cause analysis, Mean time between failure, Availability, Productivity. I. INTRODUCTION The critical machines was selected to conduct a project is Soham pre-treatment washing machine in the axle assembly line of automotive axles limited. The Soham pre-treatment washing machine is the machine used for cleaning and washing of complete axle assembly this is done after complete assembly of axle unit this washing process done before painting process The Soham pre-treatment washing machines is having two process the first process is water and chemical treatment implement to the axle coming from the conveyor as input to the machine first process is having five zones respectively. zone one is the D greasing zone and zone two is raw water zone it as two process rinse one process and rinse two process and then zone three is phosphate zone and zone four is hot water zone and zone five is D mineralized zone and it has two process rinse one process and rinse two process and then in the second process the water drying oven is the output and in this process the axle is been get dry. In the first process all the zones are having individual doors and second process is having two separate entry and exit doors. Total cycle time process is two minutes. So every two minutes one axle gets washed and come out of the machine during every start of cycle all the doors gets opened. Conveyor moves forwards axle gets positioned inside the zones. After positioning doors gets closed and pump gets on. After certain fixed timings pumps gets off. And Doors gets open. Once doors are opened conveyor will move All Rights Reserved 373

2 Here there is a frequent and repetitive breakdown related to conveyor system and doors. Problem is axle loaded conveyor gets jammed with the doors. Due to this problem the machine availability is decreased and this is a frequent breakdowns. There was a decrease in production capacity and MTBF. Hence in this project an attempt has been made to overcome the above drawbacks by incorporating new preventive maintenance schedules with safety interlock. To obtain the new preventive maintenance schedule. First all these repeated breakdowns were identified, inspected and analysed using Root cause analysis (RCA), technique like five- why method and fishbone diagram. These techniques helped to develop and improve a new preventive maintenance schedule for the machine which in turn helped in increasing availability and MTBF to certain extent and reduce the downtime and MTTR of the machine and finally to prevent the failure of equipment before it actually occurs. 1.1 Methodology of work 1. Study of existing preventive maintenance schedule 2. Study of present problem 3. Data collection of breakdowns 4. Analysis of the data collected 5. Identify the breakdowns which are most critical. 6. Finding the root causes of the breakdowns. a. Fishbone diagram b. Why-why analysis. 7. Implement of counter measures. 8. Development and improvement of a new pm schedule. II. ROOT CAUSE ANALYSIS 2.1 Root Cause Analysis & Implementation Break down Description Axle loaded conveyor gets jammed with the doors. Root cause The program logic control of the conveyor timing is not matched Physical phenomenon Door Struck, neither opened nor closed Root Cause from Why Why Analysis Problem Axle loaded conveyor gets jammed with the doors Why? Moving of conveyor time fault Why? Door Struck, neither opened nor closed Why? The program logic control of the conveyor timing is not matched Why? PLC timing should be changed Counter measure PLC timing is set to be changed, replacing the defective All Rights Reserved 374

3 Axle loaded conveyor & door struck, neither opens nor moves inside Figure 2.1 Before counter measure Now the conveyor & the door problem is Eliminated Figure 2.2 After counter measure Benefits/ results after Moving conveyor & doors are free from getting jammed; now the conveyors are moving after Eliminating PLC timing. III. RESULTS and DISCUSSION Table 1: Comparison of results before and after of counter measures of Soham Pre-treatment Washing machine Availability before (%) Availability after (%) MTBF before MTBF after MTTR before MTTR after All Rights Reserved 375

4 AVAILABILITY BEFORE AND AFTER IMPLEMENTATION OF COUNTER MEASURES % AVAILABILITY BEFORE COUNTER MEASURE IN (%) 97.22% AVAILABILITY AFTER COUNTER MEASURE IN (%) Figure 4.1 Graph Showing Comparison of Availability before and after of counter measures 120 MTBF BEFORE AND AFTER IMPLEMETATION OF COUNTER MEASURES Hrs MTBF BEFORE IMPLEMENTATION IN (Hrs) Hrs MTBF AFTER IMPLEMENTATION IN (Hrs) Figure 4.2 Graph Showing Comparison of MTBF before and after of counter measures 5 MTTR BEFORE AND AFTER IMPLEMETATION OF COUNTER MEASURES Hrs MTTR BEFORE IMPLEMENTATION IN (Hrs) 2.80 Hrs MTTR AFTER IMPLEMENTATION IN (Hrs) Figure 4.3 Graph Showing Comparison of MTTR before and after of counter All Rights Reserved 376

5 IV. CONCLUSION The use of root cause analysis helped to identify the correct causes of failures by which the suitable countermeasures are developed and implemented. The process measurable such as Availability, MTBF, and MTTR are calculated before and after the of counter measures. Continuous monitoring of processes is done after the of counter measures and following conclusions are drawn: The Breakdowns such as an Axle loaded conveyor gets jammed with the doors is completely eliminated. The Availability of Soham Pre-treatment washing machine is increased from 91.33% to 97.22%. The MTBF of Soham Pre-treatment washing machine is increased from hours to hours The MTTR of Soham Pre-treatment washing machine is decreased from 4.67 hours to 2.80 hours. REFERENCES 1. "Maintenance planning and control" - Anthony Kelly. East west press Pvt. Ltd., "Root cause analysis in aircraft final assembly" - Brown J I. Master abstract All Rights Reserved 377