Application of Ranked Positional Weight Method for Assembly Line Balancing A Case Study

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1 Applicatio of Raked Positioal Weight Method for Assembly Lie Balacig A Case Study Vivek A. Deshpade, Aad Y Joshi, Lecturer i Mechaical Egg.,, G.H.Patel College of Egg. & ch., Vallabh Vidyaagar, Gujarat. vivek_deshpade@yahoo.com, aadyjoshi@idiatimes.com Abstract: Lie balacig is the assigmet of work to statios i a lie so as to achieve the desired output with the smallest umber of workstatios []. A well-plaed ad istalled assembly lie miimizes the processig time without violatig the product requiremets. The problem i lie balacig is miimizig the idle time o the lie for all combiatios of workstatios subject to certai restrictios. The first ad foremost of these restrictios is the productio volume that is to be produced, which determies the pace at which the lie should operate. If the demad of the product should chage, it meas a chage i lie balacig. A umber of variable factors, such as lack of materials, a desig chage i the product, labour shortage or a chage i productio methods, ifluece the lie balace ad keep the problem from ever becomig too simple. If all the operatios i the fabricatio ad assembly of the product took the same time, balacig would ot preset a problem. Agai, the fact that this coditio seldom exists brigs a eed for logical, systematic method of solvig lie-balacig problems. This paper describes a heuristic approach for assembly lie balacig of trasmissio assembly lie at Mahidra & Mahidra Pvt. Ltd. I this paper the authors used raked positioal weight (RPW) method for solvig the lie-balacig problem. The performace criteria cosidered are the cycle time, lie efficiecy ad smoothess idex. Keywords: Assembly lie, Lie balacig, RPW, Lie efficiecy, Smoothess idex I. INTRODUCTION Assembly lie balacig (ALB) relates to a fiite set of work elemets or tasks, each havig a operatio processig time ad a set of precedece relatios. The objective of lie balacig is to subdivide the etwork ito several sub-statio without violatig precedece relatioships ad allocatig operatios to each statio without exceedig the cycle time []. The assembly process ca be broke dow ito workstatios, each of which cosists of a operator workig at a give locatio performig specified tasks. Each of these tasks adds value to the fial product. However, the tasks must be assiged to the various workstatios accordig to the precedece requiremets so that the idle time over the whole process is a miimum. 348 IA I order to determie a proper lie balace the followig miimum iformatio is required:. Productio volume. List of operatios ad their sequece 3. s required completig each operatio as well as the elemetal time values. Sales or marketig group should determie the productio volume. List of operatios ad their sequece should be established prior to cosiderig a lie-balacig problem. The times for various operatios, alog with the time values for the elemets withi each of these operatios, costitute probably the most importat piece of iformatio of all i the lie-balacig problem. II. LITERATURE REVIEW I this case study, authors foud that the cycle times of all the sub assembly statios are differet thereby balace delay i the existig trasmissio assembly was more ad plat capacity was iadequate. Existig productio rate was 40 uits. Also cosiderig the curret ad the future productio volume, the plat capacity should be icreased. Hece, the eed for lie balacig. III METHODOLOGY: Followig are the methods of lie balacig [3].. Largest cadidate rule. Kilbridge ad wester s method 3. Raked positio weights method Two approaches to the assembly lie balacigg problems have bee used.. Assume a fixed cycle time ad fid the optimum umber of work statios.. Assume the umber of workstatios to be fixed ad try to miimize the total delay time by miimizig the cycle time. Authors have used the first approach. Proceedigs of Iteratioal Coferece o Advaces i Machie Desig & Idustry Automatio, Jauary 0-, 007, College of Egieerig, Pue, Idia

2 Applicatio of Raked Positioal Weight Method for Assembly Lie Balacig A Case Study CYCLE FOR TRANSMISSION A) TERMINOLOGY (Table ): ASSEMBLY LINE (Table 3): Sr. Abbreviatio Descriptio Formula j Twc 3 Tsi 4 Tc 5 d E Mi. ratioal work elemet Total work cotet Work statio process time Cycle Balace Delay Lie Efficiecy j --- Twc = j Tsi B) PRECEDENCE DIAGRAM Fig. (): Refer page o. 5 j = j --- j d = (xtc Twc) / (xtc) E = (Twc) / (xtc) C) CYCLE BY MOST METHOD: Followig are the elemetal cycle times for each ad every activity of trasmissio lie. These cycle times are take by Mayard Operatio Sequece chique (MOST). Sub Assembly s (Table ): S.N. ACTIVITY COUNTER SHAFT SUB 5.37 BULL SHAFT SUB DRIVE SHAFT SUB.55 4 DIFF CASE SHAFT SUB. 5 SPLINE SHAFT SUB 4.8 REAR AXLE CARRIER SUB GEAR SHIFTER SUB.0 8 CLUTCH HOUSING SUB 7.7 D) ASSUMPTIONS:. Productio schedule is 3500 trasmissios per moth. Assume 5 workig days. So, we require 40 trasmissios / day i.e. 70 Tr. / shift if we ru two shifts.. Shift timigs: Shift I & II: 40 mi. each. 3. Available to Complete the Task (TACT) = 40 / 70 = Mi. Cycle times of all operatios are kow. CYCLE FOR TRANSMISSION S.N. ACTIVITIES A. BACKLASH ASSEMBLY MOUNT TRANS.CASE, COUNTER SHAFT, BULL CAGE LH AND RH AND 4.89 DIFFERENTIAL CASE NUMBER PUNCHING BRING SPLINE SHAFT COLLECT MATERIAL PUSH SKID TO NEXT STAGE 0. PRELOAD LH MOUNT SPLINE SHAFT. 8 CHECK BACKLASH BACKLASH LH.78 0 COLLECT MATERIAL 0.40 PUSH SKID TO NEXT STAGE 0. BACKLASH RH.78 3 BACKLASH RECHECK COLLECT MATERIAL FINAL LH BULLCAGE TIGHT.99 FINAL RH BULLCAGE TIGHT.99 7 MTG. C SHAFT FRT BEARING COVER.3 8 MTG. DRIVE SHAFT (WITHOUT TORQUE).04 9 TORQUE DRIVE SHAFT AXLE BOLT PLACING.40 B. CLUTCH HOUSING MOUNT CLUTCH HOUSING FIR C HSG. GASKET, DOWEL AND.84 G.NIPPLE. C. REAR AXLE MOUNTING MOUNT LH BRAKE.3 MOUNT LH BULL GEAR LOAD LH AXLE.59 4 AXLE BOLT PLACING.4 5 TIGHT LH AXLE.00 BOLT PLACING PRESS BOLT.3 8 MOUNT RH BRAKE.3 9 MOUNT RH BULL GEAR LOAD RH AXLE.59 AXLE BOLT PLACING.4 TIGHT RH AXLE.00 3 BOLT PLACING PRESS BOLT.3 D. BRAKE AND PTO MOUNTING BRAKE & AXLE TORQUE.9 BRAKE & AXLE TORQUE.9 3 PTO FITTING.0 E G.S. MOUNTING & TRANSMISSION TESTING MOUNT GEAR SHIFTER SUB ASSEMBLY 3.3 MOUNT TRANSMISSION CASE ON SKID.00 3 FILL OIL & TESTING 7.5 IA 349

3 STN. 3A & B 4 A, B & C 5 A, B & C Applicatio of Raked Positioal Weight Method for Assembly Lie Balacig A Case Study TRANSMISSION ASSEMBLY LINE (Table 4): ACTIVITY DESCRIPTION COUNTER SHAFT SUB BULL CAGE LH-RH SUB DIFF. CASE SUB ( PARALLEL STATIONS) DRIVE SHAFT SUB ASSLY. SPLINE SHAFT SUB (3 PARALLEL STATIONS) RAC SUB CLUTCH HSG. SUB (3 PARALLEL STATIONS) A & B GEAR SHIFTER SUB ( PARALLEL STATIONS).0 7 MOUNT TRANS.CASE, COUNTER SHAFT, BULL CAGE LH AND RH AND DIFFERENTIAL CASE 4.89 NUMBER PUNCHING 0.4 BRING SPLINE SHAFT A & B PRELOAD LH 5.79 MOUNT SPLINE SHAFT. CHECK BACKLASH 0.4 BACKLASH LH.78 ( PARALLEL STATIONS). 9 BACKLASH RH.78 BACKLASH RECHECK 0.4 FINAL LH BULL CAGE TIGHT FINAL RH BULL CAGE TIGHT.99 MTG. C SHAFT FRT BEARING COVER.3 MTG. DRIVE SHAFT.04 TORQUE DRIVE SHAFT IA TN. ACTIVITY DESCRIPTION A & B MOUNT CLUTCH HSG. FIR C HSG. GASKET, DOWEL.84 AND G.NIPPLE. MOUNT LH BRAKE.3 MOUNT LH BULL GEAR 0.4 LOAD LH AXLE.59 ( PARALLEL STATIONS).8 AXLE BOLT PLACING.4 TIGHT LH AXLE.00 BOLT PLACING 0.7 PRESS BOLT.3 3 MOUNT RH BRAKE.3 MOUNT RH BULL GEAR 0.4 LOAD RH AXLE AXLE BOLT PLACING.4 TIGHT RH AXLE.00 BOLT PLACING 0.7 PRESS BOLT.3 5 BRAKE & AXLE TORQUE.9 BRAKE & AXLE TORQUE.9 PTO FITTING MOUNT GEAR SHIFTER SUB ASSEMBLY 3.3 MOUNT TRANSMISSION CASE ON SKID.00 7 A, B & C FILL OIL & TESTING 7.50 (3 PARALLEL STATIONS) 7.50 TOTAL 9.5 STN: E) APPLICATION OF LINE BALANCING METHOD Helgeso ad Birie developed the raked positioal weight method i 9 [4]. It combies the strategies of the largest cadidate rule & kilbridge ad wester method. A RPW is computed for each elemet.

4 Applicatio of Raked Positioal Weight Method for Assembly Lie Balacig A Case Study The RPW value takes accout of the value of the elemet ad its positio i the precedece diagram. The the elemets are assiged to work statio i the geeral order of their RPW values. Elemet 7 RPW Precedece 5 & Steps:. Calculate RPW for each elemet by Step3 (Table 7): summig the elemet together with the values for the etire elemet that follows it i the arrow chai of the Elemet Elemet 0. precedece diagram List the elemets i the order of their RPW, largest at the top of the list. 3. Assig elemets to statio accordig to RPW, avoidig precedece costrait ad time cycle violatios Step (Table 5): Elemet RPW Elemet RPW Step (Table ): Elemet RPW Precedece , & & & & IV RESULT & CONCLUSION Lie Efficiecy, E = Tc Balace delay d = Twc = 9.5 7x5. 93 Tc Twc Tc X 00% = 9.77% 7x = 7x5. 93 = 8. % Smoothess Idex = {(Idle time at St.) +(Idle time at St.) +...+(Idle time at St.7) } / =.47 By applyig lie-balacig method we have icreased the productio rate from 40 uits to 70 uits. The higher value of lie efficiecy & lower value of the balace delay ad smoothess idex suggests that the lie is smooth [5]. IV REFERENCES [] Lee J. Krajewski ad Larry P. Ritzma, "Operatios Maagemet: Strategies ad Aalysis ", Ed. 5 th, Addiso- Wesley publishig Co. Ic., pp 45, 000. [] R Paeerselvam, "Productio & Operatios Maagemet ", Ed. 5 th, Pretice Hall of Idia Pvt. Ltd.., New Delhi, pp 77, 999 [3] Mikell P. Groover, "Automatio, Productio Systems ad Computer Itegrated Maufacturig ", Ed. st, Pretice Hall of Idia Pvt. Ltd., pp 44-49, 989. [4] Helgeso, W.B., ad D. P. Birie, Assembly Lie Balacig Usig Raked Positioal Weight chique, Joural of Idustrial Egieerig, Vol.,, 9, pp [5] A. P. Verma, "Idustrial Egieerigt ", Ed. st, S. K. Kataria & Sos, Delhi, pp 5, 000. IA 35

5 Applicatio of Raked Positioal Weight Method for Assembly Lie Balacig A Case Study PRECEDENCE DIAGRAM Fig. (): 7 8A 9 0 A A 8B A 3B 4A 4B 5A 5B 4C 5C A (mi.) (mi.) B 3A 3B 4A 4B 4C 5A 5B 5C A B 7 8A 8B A B A 7B 7C IA