Operations management by stevenson 9th student slides chapter 16

Chapter 16: Learning Objectives• You should be able to: – Explain what scheduling involves and the importance of good scheduling – Discuss scheduling needs in high-volume and intermediat

Chapter 16

Scheduling

Chapter 16: Learning Objectives

• You should be able to:

– Explain what scheduling involves and the importance of good scheduling – Discuss scheduling needs in high-volume and intermediate-volume

systems

– Discuss scheduling needs in job shops

– Use and interpret Gantt charts, and use the assignment method for

loading

– Discuss and give example of commonly used priority rules

– Describe some of the unique problems encountered in service systems, and describe some of the approaches used for scheduling service

systems

Scheduling

– Establishing the timing of the use of equipment, facilities

and human activities in an organization

– Effective scheduling can yield

– Cost savings – Increases in productivity

Processing Systems

– High-volume system with standardized equipment and

activities

– Output fall between the standardized-type output of

high-volume systems and the make-to-order output of job shops

– Scheduling for low-volume systems with many variations in

requirements

Hungarian Method

1 Row reduction: subtract the smallest number in each row from

every number in the row

a Enter the result in a new table

2 Column reduction: subtract the smallest number in each column

from every number in the column

a Enter the result in a new table

3 Test whether an optimum assignment can be made

a Determine the minimum number of lines needed to cross out all zeros

b If the number of lines equals the number of rows, an optimum assignment is

possible Go to step 6

c Else, go to step 4

Hungarian Method (contd.)

4 If the number of lines is less than the number of rows, modify the

table:

a Subtract the smallest number from every uncovered number in the table

b Add the smallest uncovered number to the numbers at intersections of cross-out lines

c Numbers crossed out but not at intersections of cross-out lines carry over unchanged to the next table

5 Repeat steps 3 and 4 until an optimal table is obtained

6 Make the assignments

a Begin with rows or columns with only one zero

b Match items that have zeros, using only one match for each row and each column

c Eliminate both the row and the column after the match

Example: Hungarian Method

workers for the following data:

Worker

Job

Example: Hungarian Method (contd.)

Worker

Row minimum

Job

Worker

Job

Subtract the smallest number in each row from every number in the row

Example: Hungarian Method (contd.)

Worker

Subtract the smallest number in each column from every number in the column

Worker

Job

Column min 0 1 0 2

Example: Hungarian Method (contd.)

Worker

Job

Determine the minimum number of lines needed to cross out all zeros (Try to cross out as many zeros as possible when drawing lines

Since only three lines are needed to cross out all zeros and the table has four rows, this is not the optimum Note: the smallest uncovered value is 1

Example: Hungarian Method (contd.)

Worker

Job

Subtract the smallest uncovered value from every uncovered number, and add

it to the values at the intersection of covering lines

Worker

Job

Example: Hungarian Method (contd.)

Determine the minimum number of lines needed to cross out all zeros (Try to cross out as many zeros as possible when drawing lines

Since four lines are needed to cross out all zeros and the table has four rows, this an optimal assignment can be made

Job

Example: Hungarian Method (contd.)

Make assignments: Start with rows and columns with only one zero Match jobs with machines that have a zero cost

Assignment Cost

• Sequencing

– Determine the order in which jobs at a work center will be processed

• Priority rules

– Simple heuristics used to select the order in which jobs will be

processed

• FCFS - first come, first served

• EDD - earliest due date

• CR - critical ratio

• S/O - slack per operation

• Rush - emergency

Operations Strategy

– Goods and services can be made or delivered in a timely

manner

– Resources can be used to best advantage

– Customers will be satisfied

scheduling to strategy and competitive advantage