Question

3. The operation manager of a body and paint shop has five cars to schedule for repair. He would like to minimize throughput time to complete all work on these cars. Each car requires body work prior to painting. The estimates of the times required to do the body and paint work on each are listed below. Car Body Work (Hours) Paint (Hours) JA 12 B 17 6 14 10 C 19 D 3 E 12 4 5 (a) Determine the job sequence using the Johnson rule. (b) How much idle time is related to painting? (use a chart to find out the idle time for painting).

Answer 1

(a) Job Sequence using Johnson Rule.
CAR	BODY WORK(HOURS)	PAINT(HOURS)
A	12	6
B	7	4
C	9	10
D	3	4
E	12	5

1. The smallest time is located in Car D i.e. 3 Hours. Since the work is in Body Work, schedule this as first job. Now eliminate Job D from further consideration.

D

2. Now the smallest time is located in Car B i.e. 4 Hours. Since it is in the Paint, schedule this as last job and now eliminate Job B from consideration.

D

B

3. Now the smallest time is located in Car E i.e. 5 Hours. Since it is in the Paint, schedule this as second last job and now eliminate Job E from consideration.

D

E

B

4. Now the smallest time is located in Car A i.e. 6 Hours. Since it is in the Paint, schedule this as third car and now eliminate Job A from consideration.

D

A

E

B

5. Now the smallest time is located in Car C i.e. 9 Hours. This is the last car.

D

C

A

E

B

Thus sequence is D-C-A-E-B

(b) Idle time related to painting

Total hours in Painting = D(4)+C(10)+A(6)+E(5)+B(4)=29 Hours

Total hours Body work = A(12)+B(7)+C(9)+D(3)+E(12)=43 Hours

Idle time = 14 Hours