Don't Bother Me
Don't Bother Me
Don't Bother Me
Rohit Kapoor
Case Background
Mrs. Santha Owner small assembly shop
New order for two types of sub-assemblies
Production Line A
Current production 315 units/day New order size of 420 units/day (% inc. 33.33%) Contribution Rs. 30/unit 7 workers Regular wage Rs. 18/hr/worker Overtime wage Rs. 30/hr/worker
10
1 7 4
11 13
5
2
14 12 15
16
Organization of Line A
Worker Activities Station Time 1 1, 3 70 1 2, 5 70 1 4, 8 70 1 6, 9, 13 70 1 7, 10, 11 70 1 14, 15 60 1 12, 16 70
t = 480 sec Time available = 7 * 60 * 60 = 25200 sec Actual cycle time = 25200/315 = 80 sec Production capacity = 25200/70 = 360 units/day Max OT = 2 hrs = 7200 sec Additional max production = 7200/70 = 102 (approx.) Max production = 360 + 102 = 462 units/day Max requirement = 420 units/day, implies feasible
Line A
OT required = (420 360) * 70/(60 * 60) = 1.167 Hrs OT Cost/Day = 1.167 (OT) * 7 (Workers) * (Rs. 30/hr/worker) = Rs. 245
Line A Option 1
CT Planned = 25200/420 = 60 sec Theoretical min. no. of workers reqd. = 480/60 = 8 Additional worker required = 8 7 = 1
Worker Activities Station Time 1 2 50 1 1, 5 50 1 3, 8 60 1 4, 6 60 1 9, 13 60 1 7, 14 60 1 10, 11 60 1 12, 15 40 1 16 40
Actual no. of workers reqd. = 9 CT achieved = 60 sec, implies; capacity = 420 units/day Training costs = Rs. 6000 * 2 = Rs. 12000 Regular wage = 2 * 18 * 7 = Rs. 252/day
Line A Option 2
Worker Activities Station Time 2 1, 2, 3 120 1 4, 6 60 1 5, 7, 8, 9 60 1 10, 11 60 1 14, 15 60 2 12, 13, 16 120
No. of workers required = 8 Cycle time = 60 sec Capacity = 420 units/day Balance eff. = 100% Training cost = Rs. 6000 Regular wage = 1 * 7 * 18 = Rs. 126
Line B
Mrs. Uma Two workers New order size = 210 units/day Current organization of line B
Worker 1 Activities a, b, c, d Station Time 180 1 e, f, g, h 180
Production capacity = 25200/180 = 140 units/day % inc. in reqt. = (210-140)/140 = 50% OT required/day = (210-140) * 180/(60 * 60) = 3.5 hrs Max OT available = 2 hrs
Line B Option 1
CT Planned = 25200/210 = 120 sec Theoretical min. no. of workers reqd. = 360/120 = 3 Additional worker required = 3 2 = 1
Worker Activities Station Time 1 a, b, d 110 1 c, e 120 1 f, g, h 130
CT achieved = 130 sec, implies; capacity = 193 units/day OT required = (210 193) * 130/(60 * 60) = 0.613 hrs OT required (1% rejection) = 0.613/0.99 = 0.62 hrs Training costs = Rs. 6000; Regular wage = 1 * 18 * 7 = Rs. 126/day; OT cost/day = 3 * 0.62 * 30 = Rs. 55.8; Rejection Cost/day = (210 193) * 0.01 * 420 = Rs. 71.4. Total cost/day = Rs. 253.21
Line B Option 2
Worker Activities Station Time 1 a, b 90 1 c, d 90 1 e, f 90 1 g, h 90
No. of workers required = 4 Cycle time = 90 sec Capacity = 280 units/day Balance eff. = 100% Training cost = 2 * 6000 = Rs. 12000 Regular wage/day = 2 * 7 * 18 = Rs. 252
Assembly Line
Key Issues in Managing Assembly Lines
Time standards Assembly line balancing Rebalancing Material availability/Materials and Supplier relations. Worker incentives Capacity Planning Plant Loading/Production planning Product design Product Mix Sequencing (to maintain balance)