A manager wants to assign tasks to workstations

Problem 6-2

A manager wants to assign tasks to workstations as efficiently as possible, and achieve an hourly output of 331/3 units. Assume the shop works a 60-minute hour. Assign the tasks shown in the accompanying precedence diagram (times are in minutes) to workstations using the following rules:

Picture

a.

In order of most following tasks. Tiebreaker: greatest positional weight.

Work Station

                Tasks

I

II

III

IV

b.

In order of greatest positional weight.

Work Station

                 Tasks

I

II

III

IV

c.

What is the efficiency? (Round your answer to 2 decimal places. Omit the "%" sign in your response. )

  Efficiency

%

Problem 6-3

A manager wants to assign tasks to workstations as efficiently as possible, and achieve an hourly output of 4 units. The department uses a working time of 56 minutes per hour. Assign the tasks shown in the accompanying precedence diagram (times are in minutes) to workstations using the following rules:

Picture

a.

In order of most following tasks. Tiebreaker: greatest positional weight.

Work Station

  Tasks

I

II

III

IV

b.

In order of greatest positional weight.

Work Station

Tasks

I

II

III

IV

c.

What is the efficiency? (Round your answer to 2 decimal places. Omit the "%" sign in your response. )

   Efficiency

 %

Problem 6-8

A shop works a 400-minute day. The manager of the shop wants an output of 200 units per day for the assembly line that has the elemental tasks shown in the table. Do the following:

Task

Immediate Predecessor

Task Time (minutes)

a

-

0.5

b

a

1.4

c

a

1.2

d

a

0.7

e

b, c

0.5

f

d

1.0

g

e

0.4

h

g

0.3

i

f

0.5

j

e, i

0.8

k

h, j

0.9

m

k

0.3

b.

Assign tasks according to the most following tasks rule.

Work Station

            Following Tasks

1

2

3

4

5

c.

Assign tasks according to the greatest positional weight rule.

Work Station

            Following Tasks

I

II

III

IV

V

d.

Compute the balance delay for each rule. Which one yields the better set of assignments in this instance? (Omit the "%" sign in your response.)

  Balance delay: both part b and c are

 %

Problem 6-18

For the set of tasks given below, do the following:

Task

Task Time (seconds)

Immediate Predecessor

A

45

-

B

11

A

C

9

B

D

50

-

E

26

D

F

11

E

G

12

C

H

10

C

I

9

F, G, H

J

10

I

193

Assign tasks to stations for a desired output of 500 units in a 7-hour day to balance the line using the longest operation time heuristic. Break ties with the most following tasks heuristic. Calculate the percentage idle time for the line. Use the actual bottleneck cycle time in your calculation. (Round your percentage of idle time to 2 decimal places. Omit the "%" sign in your response.)

Work Station

Task

I

II

III

IV

  Percentage of idle time

%

Problem 7-1

An analyst has timed a metal-cutting operation for 50 cycles. The average time per cycle was 10.9 minutes, and the standard deviation was 1.20 minutes for a worker with a performance rating of 139 percent. Assume an allowance of 16 percent of job time. Find the standard time for this operation. (Do not round intermediate calculations. Round your final answer to 2 decimal places.)

  Standard time

minutes

Problem 7-4

Given these observed times (in minutes) for four elements of a job, determine the observed time (OT) for each element. Note: The second element only occurs every other cycle. (Round your answers to 2 decimal places.)

CYCLE

  Element

   1

2

    3

4

  5

6

1

4.1

4.0

4.4

4.1

4.1

4.1

2

      -

1.5

-

1.8

-

1.4

3

3.2

3.2

3.6

3.2

3.3

3.3

4

2.7

4.1

2.7

2.8

2.8

2.8

Element

    Observed Time

1

2

3

4

Problem 7-5

Given these observed times (in minutes) for five elements of a job, determine the observed time (OT) for each element. Note: Some of the elements occur only periodically. (Round your answers to 2 decimal places.)

CYCLE

Element

  1

  2

3

4

 5

6

1

2.1

2.0

2.6

2.1

2.1

-

2

-

1.7

-

1.0

-

1.2

3

3.4

3.5

3.3

3.8

3.4

3.3

4

4.0

-

-

5.1

-

-

5

1.4

1.4

2.0

1.5

1.5

1.4

Element

Observed Time

1

2

3

4

5

Problem 7-6

Using the following data, develop an allowance percentage for a job element that requires the worker to lift a weight of 30 pounds while (1) standing in a slightly awkward position, (2) in light that is very inadequate standards, and (3) with intermittent very loud noises occurring. The monotony for this element is low. Include a personal allowance of 5 percent and a basic fatigue allowance of 4 percent of job time. (Leave no cells blank - be certain to enter "0" wherever required. Omit the "%" sign in your response.)

Percent

Percent

  A.

Constant allowances:

4. Bad light:

1. Personal allowance

5

    a. Slightly below recommended

0

2. Basic fatigue allowances

4

    b. Well below

2

  B.

Variable allowances:

    c. Very inadequate

5

1. Standing allowance

2

5. Atmospheric conditions

2. Abnormal position allowance:

    (heat and humidity)—variable

0-10

     a. Slightly awkward

0

6. Close attention:

     b. Awkward (bending)

2

    a. Fairly fine work

0

     c. Very awkward (lying, stretching)

 7

    b. Fine or exacting

2

3. Use of force or muscular energy

    c. Very fine or very exacting

5

     (lifting, pulling, or pushing):

7. Noise level:

     Weight lifted (in pounds):

    a. Continuous

0

          5

0

    b. Intermittent—loud

2

        10

1

    c. Intermittent—very loud

5

        15

2

    d. High-pitched—loud

5

        20

3

8. Mental strain:

        25

4

    a. Fairly complex process

1

        30

5

    b. Complex or wide span of attention

4

        35

7

    c. Very complex

8

        40

9

9. Monotony:

        45

11

    a. Low

0

        50

13

    b. Medium

1

        60

17

    c. High

4

        70

22

10. Tediousness:

     a. Rather tedious

0

     b. Tedious

2

     c. Very tedious

5

  Factor

%

  Personal

  Fatigue

  Standing

  Lifting

  Bad Light

  Noise Level

  Monotony

  Total

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