Session 15
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
1
Production Activity Control in the
MPC System
2
Basic Data
3
Routing Data and Operation
Setback Chart
4
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 sevenday week.
_____________________________________________________
Order
(B)iff
(G)riffin
(H)erbie
(K)errie
Arrival
date
Nov. 10
Nov. 10
Nov. 12
Nov. 14
Job/WC Processing time (days)
routing WC 1
WC 2
WC 3
1-3-2
1
3
1
2-3-1
2
2
2
3-2-1
3
1
2
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.
5
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 Processing time (days)
routing WC 1
WC 2
WC 3
1-3-2
1
3
1
2-3-1
2
2
2
3-2-1
3
1
2
2-1-3
1
3
1
6
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).
7
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.
8
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
Date job arrived
at this machine
6-23
6-24
7-01
6-19
Job due
date__
8-15
9-10
8-01
8-17
*Note: This is the final operation for each of these jobs.
___________________________________________________________
9
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
Job due
date__
8-15
9-10
8-01
8-17
*Note: This is the final operation for each of these jobs.
10
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
11
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.
12
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
13
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
14
Finite Loading
15
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.
16
The Bundy Company
Machine
center
Order routing
A
3-1-2
K
2-3-1
P
3-2-1
Processing time
at machine center
___(in days)____ Order
1
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.
17
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
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
19
Process Design Impact Scheduling
• Batch Manufacturing: Work Orders
• Repetitive Manufacturing: JIT/Kanban
20