Lecture 13
Production Activity Control
Books
• Introduction to Materials Management, Sixth Edition, J. R. Tony Arnold, P.E., CFPIM, CIRM, Fleming
College, Emeritus, Stephen N. Chapman, Ph.D., CFPIM, North Carolina State University, Lloyd M.
Clive, P.E., CFPIM, Fleming College
• Operations Management for Competitive Advantage, 11th Edition, by Chase, Jacobs, and Aquilano, 2005,
N.Y.: McGraw-Hill/Irwin.
• Operations Management, 11/E, Jay Heizer, Texas Lutheran University, Barry Render, Graduate School of
Business, Rollins College, Prentice Hall
Objectives
•
•
•
•
•
•
Production activity control
Gantt chart
Critical ratio scheduling
Finite loading
Scheduling
Assignment method
Production Activity Control
• PAC in the MPC System
– Shop Floor Control
– Vendor Scheduling
• Production Activity Control Techniques
–
–
–
–
Basic Data
Gantt Charts
Priority Scheduling
Finite Loading
• Process Design Impact on Scheduling
– Batch Manufacturing – Work Orders
– Repetitive Manufacturing – JIT
3
Production Activity Control in the MPC System
4
Basic Data
Routing Data and Operation Setback Chart
6
Gantt Charts
The incoming orders at Tom's Sailboard follow different routes through the shop but all
orders must stop at each of the three work centers in the plant. The table below shows
all tasks for four jobs that arrive over 5 days and need to be scheduled at the company.
It is currently November 10 and Tom works a seven-day week.
_____________________________________________________
Order
(B)iff
(G)riffin
(H)erbie
(K)errie
Arrival Job/WC Processing time (days)
date
routing WC 1
WC 2
WC 3
Nov. 10 1-3-2
1
3
1
Nov. 10 2-3-1
2
2
2
Nov. 12 3-2-1
3
1
2
Nov. 14 2-1-3
1
3
1
Assume that the new material for all orders is in stock and that a
first-come/first-served sequencing rule is used at all work centers. All three
work centers are idle as work begins on orders B and G on November 10.
Tom’s Sailboard
a. Construct a Gantt chart depicting the processing and
idle times for the three work centers for these four jobs.
Order
(B)iff
(G)riffin
(H)erbie
(K)errie
Arrival
date
Nov. 10
Nov. 10
Nov. 12
Nov. 14
Job/WC
routing
1-3-2
2-3-1
3-2-1
2-1-3
Processing time (days)
WC 1
WC 2
WC 3
1
3
1
2
2
2
3
1
2
1
3
1
Tom’s Sailboard
b.
How many days does each job wait in queue for processing at work center 2?
The determination of how long jobs wait at work center 2 is as follows: B and G
are processed immediately at work center 2, order K must wait 1 day (11/14) and
order H waits 4 days (11/12, 11/13 at WC3) and (11/16 and 11/17 at WC2).
Priority Sequencing Rules
•
•
•
•
First Come, First Served
Shortest Operation Next
Earliest Due Date
Order Slack: (Time Remaining until Due Date –
Sum of Remaining Setup and Run Time)
• Slack per Operation
• Critical Ratio: (Due Date-Now)/(Lead Time
Remaining)
________________________________________
Lead Time Remaining includes setup, run, move
and queue time for all remaining operations.
Knox Machine
2. The jobs below are waiting to be processed at the P&W Grinder at the Knox Machine
Company. (There are no other jobs and the machine is empty.)
__________________________
Job
A
B
C
D
Machine processing
time (in days)*__
4
1
5
2
6-23
6-24
7-01
6-19
Date job arrived
at this machine
8-15
9-10
8-01
8-17
Job due
date__
*Note: This is the final operation for each of these jobs.
___________________________________________________________
Knox Machine: Solution
a.
The production manager has heard about three dispatching rules: the
Shortest Operation Next Rule, the First-Come/First-Served Rule, and the
Earliest Due Date Rule. In what sequence would these jobs be processed
at the P&W grinder if each rule was applied?
1.
2.
3.
Job
A
B
C
D
The shortest operation next rule: B-D-A-C
The first-come, first-served rule: D-A-B-C
The earliest due date rule: C-A-D-B
Machine processing
time (in days)*__
4
1
5
2
Date job arrived
at this machine
6-23
6-24
7-01
6-19
*Note: This is the final operation for each of these jobs.
Job due
date__
8-15
9-10
8-01
8-17
Knox Machine: Solution
b. If it's now the morning of July 10 and the Shortest
Operation Next Rule is used, when would each of
the four jobs start and be completed on the P&W
grinder? (Express your schedule in terms of the
calendar dates involved, assuming that there are 7
working days each week.)
P & W Grinder
Job B
Date
7/10
D
7/11
A
7/12
7/13
7/14
7/15
C
7/16
7/17
7/18
7/19
7/20
7/21
Critical Ratio Scheduling
Eight weeks remain for constructing the a 50foot yacht.
Assume that each week consists of 5 work days, for a total
lead time of 40 days. The work required to complete the
yacht comprises 10 operations, 4 days for each.
Yacht Project Example
a.
On Tuesday morning of week 3, 3 of the 10
operations had been completed and the yacht
was waiting for the fourth operation. What's the
critical ratio priority?
Time Remaining 40  11
Critical Ratio 

 1.04
Work Remaining
28
Yacht Project Example
b. What's the critical ratio priority if only 2 of the
10 operations are completed by Tuesday
morning of week 3?
Time Remaining 40  11
Critical Ratio 

 .91
Work Remaining
32
Finite Loading
The Bundy Company
The Bundy Company produces for three products
(A, K, and P). Each order goes through the same
three machine centers, but not necessarily in the
same sequence. Each order must be finished at a
machine center before another can be started.
Orders cannot be split. The shop works a single
eight-hour shift five days per week. Assume that
the time to move between machines is negligible.
each machine center is operated eight hours per
day. All three machines are currently available for
scheduling, and no further orders will arrive.
The Bundy Company
Machine
center
Order routing1
A
3-1-2
K
2-3-1
P
3-2-1
Processing time
at machine center
___(in days)____
Order
2
3
due date
1
3
2
14
3
1
3
12
2
3
4
10
Note: Order due dates are fixed based on the shop calendar. It
is now 8:00 A.M. Monday (day 1), Monday of next week is
day 6, etc.
The Bundy Company
Using the horizontal loading procedure with earliestdue-date priority sequencing rule, prepare a Gantt chart
showing the production schedule for the three orders
above.
Machine
Center 1
P-3
Machine
K–1
Center 2
Machine
Center 3
P-2
P-1
1
K-3
2
A-3
K-2
3
4
5
6
A-2
A-1
7
8
9
10 11 12 13 14 15 16 17 18
The Bundy Company
Using the vertical loading procedure and the shortestoperation-next priority sequencing rule, prepare a Gantt
chart showing the production schedule for the three
orders above.
Machine
Center 1
K-3
A-2
Machine
K-1
Center 2
Machine
Center 3
A-3
A–1
1
P-3
2
P-2
K-2
3
4
P-1
5
6
7
8
9
10 11 12 13 14 15 16
Process Design Impact Scheduling
• Batch Manufacturing: Work Orders
• Repetitive Manufacturing: JIT/Kanban
Scheduling
What is Scheduling?
• Last stage of planning before production occurs
• Specifies when labor, equipment, and facilities are
needed to produce a product or provide a service
Scheduled Operations
• Batch Production
• Process Industry
– Linear programming
– Aggregate planning
– EOQ with non– Master scheduling
instantaneous
– Material requirements
replenishment
planning (MRP)
• Mass Production
– Assembly line balancing
– Capacity requirements
• Project
planning (CRP)
– Project -scheduling
techniques (PERT, CPM)
Objectives in Scheduling
•
•
•
•
•
Meet customer due dates
Minimize job lateness
Minimize response time
Minimize completion time
Minimize time in the system
• Minimize overtime
• Maximize machine or labor
utilization
• Minimize idle time
• Minimize work-in-process
inventory
Shop Floor Control (SFC)
• Schedule and monitor day-to-day job shop production
• Also called production control and production activity
control (PAC)
• Performed by production control department
– Loading - check availability of material, machines, and
labor
– Sequencing - release work orders to shop and issue
dispatch lists for individual machines
– Monitoring - maintain progress reports on each job
until it is complete
Loading
• Process of assigning work to limited resources
• Perform work with most efficient resources
• Use assignment method of linear programming to
determine allocation
Assignment Method
1. Perform row reductions
–
subtract minimum value in each
row from all other row values
2. Perform column reductions
–
subtract minimum value in each
column from all other column
values
3. Cross out all zeros in matrix
–
use minimum number of horizontal
and vertical lines
4. If number of lines equals number of
rows in matrix, then optimum
solution has been found. Make
assignments where zeros appear
‾
‾
‾
‾
Else modify matrix:
subtract minimum uncrossed value
from all uncrossed values
add it to all cells where two lines
intersect
other values in matrix remain
unchanged
5. Repeat steps 3 and 4 until optimum
solution is reached
Assignment Method
Initial
Matrix
Bryan
Kari
Noah
Chris
1
10
6
7
9
Row reduction
5
4
2
5
0
0
1
1
1
2
0
0
5
4
1
6
PROJECT
3
6
4
5
4
2
5
2
6
5
4
10
6
6
10
Column reduction
Cover all zeros
3
2
0
3
3
2
0
3
0
0
1
1
1
2
0
0
4
3
0
5
Number lines  number of rows so modify matrix
0
0
1
1
1
2
0
0
4
3
0
5
Assignment Method
Modify matrix
1
0
1
0
0
2
0
3
2
1
1
0
Cover all zeros
1
0
1
0
0
2
0
3
2
1
1
0
2
1
0
3
2
1
0
3
Number of lines = number of rows so at optimal solution
Bryan
Kari
Noah
Chris
1
1
0
0
1
PROJECT
2
3
0
1
0
2
3
2
1
0
4
2
1
0
3
Bryan
Kari
Noah
Chris
1
10
6
7
9
Project Cost = (5 + 6 + 4 + 6) X $100 = $2,100
PROJECT
2
3
4
5
6 10
2
4
6
6
5
6
5
4 10
Assignment Method - Setup
Solution goes here
Only 1 leader can
be assigned to
each project
Click “Solve” for
solution
Sum of all rows and
columns = 1
Assignment Method - Solution
Assignments indicated by 1
Cost of solution
End of Lecture 13