GOM3
Exercise
Return to King for Using More Machines
14
13
12
11
10
9
8
7
6
12
5
2
5
3
4
C
5
6
10
2
10
3
4
--
4
D
C
B
A
Efficiency (%)
Total Hourly Output
Cycle Time (min)
Machine Times (min)
Type of next machine
Number of Machines
Return to King for Using More Machines
40
1
C
14
36
1
C
13
30
2
1
2
A
12
30
2
1
2
2
D
11
30
2
2
2
2
C
10
24
2
2
B
9
20
3
2
3
2
C
8
18
2
3
2
A
7
15
4
2
3
4
C
6
12
5
2
5
3
4
C
5
6
10
2
10
3
4
--
4
D
C
B
A
Efficiency (%)
Total Hourly Output
Cycle Time (min)
Machine Times (min)
Type of next machine
Number of Machines
Question:
The model J Wagon is to be assembled on a conveyor belt. Five hundred wagons are required per day. Production time per day is 420 minutes, and the assembly steps and times for the wagon are given in the following Exhibit. Assignment: find the balance that minimizes the number of workstations, subject to cycle time and precedence constraints.
195
J
Tighten bolt and nut
9
K
F, G, H, I
Position wagon handle shaft on front axle assembly and hand fasten bolt and nut
8
J
E
Position front wheel #2 and fasten hubcap.
12
I
E
Position front wheel #1 and fasten hubcap.
12
H
C
Position rear wheel #2 and fasten hubcap.
12
G
C
Position rear wheel #1 and fasten hubcap.
12
F
D
Tighten front axle assembly screws
15
E
--
Position front axle assembly and hand fasten with four screws to nuts
50
D
B
Tighten rear axle support screws to nuts
9
C
A
Insert rear axle
11
B
--
Position rear axle support and hand fasten four screws to nuts.
45
A
TASKS THAT MUST PRECEDE
DESCRIPTION
TASK TIME IN SECONDS
TASK
1. Draw a Precedence Diagram.
A
B
C
F
J
D
E
H
I
G
K
45 sec
50 sec
11 sec
15 sec
9 sec
12 sec
12 sec
12 sec
12 sec
8 sec
9 sec
2. Determine workstation cycle time. Here we have to convert to seconds because
Our task time are in seconds
3. Determine the theoretical minimum number of workstations required (the
Actual number may be greater.
A
B
C
F
J
D
E
H
I
G
K
45 sec
50 sec
11 sec
15 sec
9 sec
12 sec
12 sec
12 sec
12 sec
8 sec
9 sec
WS1
WS2
WS3: B,E,C,F
WS4: G,H,I,J
WS5
0
K
1
J
2
F,G,H or I
4
C or E
5
B or D
6
A
NUMBER OF FOLLOING TASKS
TASK
4. Select assignment rules
a. assign tasks in order of the largest
number of following tasks
b. assign tasks in order of longest task
time
5. Make task assignments to form Workstation 1,
Workstation 2…..
6. Calculate efficiency: assume 5 first?
7. Evaluate the solution. An efficiency of 77
percent indicates an imbalance or idle time of
27 percent across the entire line.
8. Is a better balance possible? Yes, Try balancing the line with rule b. and
break ties with rule a. (This will give yo0u a feasible four-station balance.
Question
A company is considering adding a new feature that will increase unit sales by 6 percent and product cost by 10 percent. Profit is expected to increase by 16 percent of the increased sales. Initially the product cost incurred by the company was 63 percent of the sales price. Should be the feature be added?
Let the sales be $100M.
Solution
Day 1
Problem 1
Sales increase by 6% = $100M x 6% = $6M
Benefits: Profits increase by 16% of the increased sales = $6M x 16% = $
Cost: Increase product cost by 10% = ($100M x 63%) x 10% = $
Because costs exceed benefits, the new feature should not be added.
Question
An automobile manufacturer is considering a change in an assembly line that should save money due to a reduction in labor and material cost. The change involves the installation of four new robots that will automatically install windshields. The cost of the four robots, including installation and initial programming, is $400,000. Current practice is to amortize the initial cost of robots over two years on a straight-line basis. The process engineer estimates that one full-time technician will be needed to monitor, maintain, and reprogram the robots on an ongoing basis. This person will cost approximately $60,000 per year. Currently, the company uses four full-time employees on this job and they each make about $52,000 per year. One of these employees is a material handler, and this person will still be needed with the new process. To complicate matters, the process engineer estimates that the robots will apply the windshield sealing material in a manner that will result in a savings of $ per windshield installed. How many automobiles need to be produced over the next two years to make the new robots an attractive investment? Due to the relatively short horizon, do not consider the time value of money.
Solution:
Cost of the current process over the next two years is just the cost of the four full-time employees.
$52,000/employees x 4 employees x 2 years = $416,000
The cost of the new process over the next two years, assuming the robot is completely costed over that time, is the following:
($52,000/material handler + $60,000/technician) x 2 + $400,000/robots - $ x autos
Equating the two alternatives:
$416,000 = $624,000 - $ x autos
Solving for the break-even point:
-$208,000/-$ = 832,000autos
This indicates that to break even, 832,000 autos would need to be produced with the robots over the next two years.
ISO 9000 series
Quality system
9001: model for quality assurance in design, production, installation, and servicing
9002: model quality assurance in production and installation.
9003: model for quality assurance in final inspection test.
Guidelines for Use
9000: quality management and quality assurance standards—guidelines for selection and use.
Quality management and quality elements--guidelines
Quality System
Design/
development
Procurement
Production
Installation
Servicing
ISO9002
Design/
development
Procurement
Production
Installation
Servicing
ISO9003
ISO 9001
Question
Management is trying to decide whether Part A, which is produced with a consistent 3 percent defective rate, should be inspected. If it is not inspected, the 3 percent defectives will go through a product assembly phase and have to be replaced later. If all Part A’s are inspected, one-third of the defectives will be found, thus raising the quality to 2 percent defectives.
a. should the inspection be done if the cost of inspecting is $ per unit and the cost of replacing a defective in the final assembly is $?
b. suppose the cost of inspecting is $ per unit rather than $. Would this change your answers in “a”?
Solution:
Should Part A be inspected?
.03 defective with no inspection
.02 defective with inspection
a. This problem can be solved simply by looking at the opportunity for 1 percent improvement.
Benefit = .01 ($) = $
Cost of inspection = $
Therefore, inspect and save $ per unit
A cost of $ per unit to inspect would be $ greater than the savings, so inspection should not be performed.
