Question

An automobile final assembly plant has an annual production capacity of 200,000 cars. The plant operates 50 weeks/yr, 2 shifts/day, 5 days/week, and 8.0 hours/shift. It is divided into three departments: (1) body shop, (2) paint shop, and (3) trim-chassis-final department. The body shop welds the car bodies using robots, and the paint shop coats the bodies. Both of these departments are highly automated. Trim-chassis-final has no automated workstations. Cars are moved by a continuous conveyor. There are 15.0 hours of work content time on each car in this department. If the average manning level is 2.2, balancing efficiency = 93%, proportion uptime = 95%, and a repositioning time of 0.15 min is allowed for each worker, determine

(a) hourly production rate of the plant.
(b) number of workers and workstations in trim-chassis-final.
(c) What is the average labor cost per car in trim-chassis-final if the hourly worker rate = $35 and fringe benefits add $20/hr. Ignore cost of supervision, maintenance, and other indirect labor.

Answer 1

a) Rp= 200,000 / (50 X 10 X 8)= 50.0 units /hr

b) Tc= E/Rp= 60 (0.95) /50 =1.14 min

Ts= Tc - Tr = 1.14 - 0.15 = 0.99 min

w= Min Int > Twc/EbTs= 15.0 X 60 / (0.93 X 0.99) ) 944.5 rounded: 978 workers /shift

Total number of workers = 1956 over 2 shifts

n= w/M = 978/2.2 = 444.3 rounded 445 stations

Annual workload WL = 200,000 cars x 15/hr/car = 3,000,000 hr/work

with 1956 workers,= 1956 (50 X 10 X 8) = 3,912000 hr

This doesn´t include E, Eb and Er

E= 0.95 (given), Eb= 0.93 and Er= 0.99/1.14= 0.8684

Usable service time: 3, 912,000 (0.95) (0.93( (0.8684) = 3,912,000(0.767) = 3,001, 409 hr

C) the plant operates (50 weeks/yr)(10 shifts/week) (8 hr(shift) = 4000 hr/yr

Total hourly labor rate= $30 + $15= $45/hr

total labor cost = (1956 workers) (2000 hr/wrk-yr) ($45/hr) = $176,040,000

LAbor cost in trim-chassis-final per car= 176,040,000/200,000 = $880.20/car