1. PRODUCTION ACTIVITY CONTROL (PAC)
Shop floor control

2. PLANNING AND CONTROL SYSTEM
Strategic plannig
Sales &Operation Plan (aggregated)
Master Production Schedule (MPS)
Material Requirements Plan
Purchasing Control
Production Control (PAC)
Input /Output Control
Detailed Capacity Req. P.
Rough-cut Capacity Plan
Resource Planning
Plan
Execution
Demand
Forecasts
Customers Orders
Resources

3. Production Activity Control – PAC Shop Floor Control
PAC – the lowest level of production management system in a company
PAC - regulates the work flow through the production system
Master scheduling (MPS/MRP) is a Planning activity
Production Activity Control is an Execution Control activity

4. Production Activity Control
Master Production Scheduling
Material Reguirements Planning
Capacity Reguirements Planning
Manufacturing processes
Production Activity Control
Scheduling, Dispaching, Monitoring
Instructions
Planned Orders
Data
Production Activity Control transfers the data from higher levels of production planning (MPS, MRP, CRP) into manufacturing processes instructions.
It also tranforms data from shop floor level into information for higher planning levels.

5. Production Activity Control
Production Activity Control scope, complexity, principles, methods depend on production continuity
Production continuity could be:
flow shop type (continuous flow)
job shop type (intermittent flow, irregular flow)
Production control systems:
Flow control - for continuous production flow
Order control - for intermittent production flow (irregular flow, not continuous production flow)

6. Intermittent production flow
The products are produced based on customer's orders, on a small scale.
The flow of production is intermittent (irregular)
The large varieties of products are produced
The products are different sizes. No continuous flow of the same size.
The production system is very flexible
The types of intermittent production flows:
Project production flows
Jobbing production flows
Batch production flows
Examples:
Tailor
Goldsmith
Furniture to order, car to order, ship to order
Make to order industry

7. Continuous production flow
The flow of production is continuous.
The products are standardized.
The products are produced in anticipation of demand, based on demand forecast.
Standardized routing sheets and schedules are prepared.
The types of a continuous production flows:
Mass production flows
Apparatus (prosess) production flows.
Examples:
Food industry
Fuel industry
Cosmetics industry
Washing and hygiene industry (soaps, tooth pastes, etc)

8. Production Activity Control
The main elements of PAC
Scheduling – to develop detailed schedule based on timely knowledge and data which will ensure that all the production requirements are fulfilled .
Dispatching – to implement the schedule taking into account the current status of the production system (orders releasing)
Monitoring – to monitor the status of vital components in the system, either with the naked eye or by using technology based methods.

9. Order Control The goals of Order Control:
The objective of Order Control is to optimize the particular order flow through the facility so that production aims are met
The goals of Order Control:
High percentage of orders completed on time
High utilisation of workers and facilities
Low work-in-process (WIP) inventory
Minimize customer wait time
Minimize costs

10. Job shop scheduling
The main Order Control activity is job shop scheduling
Scheduling involves assigning due dates to specific jobs (when to start the job, when to finish the job)
Job shop scheduling involves:
Allocating jobs to specific work centers (loading)
Prioritizing all jobs at each work center (sequencing)
Release jobs to workcenters (dispaching)
Revising priorities as changes occur
Monitoring the progress of jobs
Job shop scheduling is used to all operations in a factory, hospital, university or office. For service operations, „job” is replaced by patient, customer or whatever flows through the facility. The work center may be a desk, office, room, or skill speciality.

11. Production Activity Control
Job shop control process
Start
Allocate jobs to work centers (Loading)
Prioritize all jobs at work centers (Sequencing)
Release jobs to workcenters (Dispaching)
Review jobs progress
Uncompleted jobs
Completed jobs

12. Scheduling techniques
There are two scheduling techniques to assigning due dates to specific jobs:
Forward scheduling
Backward scheduling
Forward scheduling – an approach to scheduling that starts from the present time and schedules each job to start at the earliest possible moment. Advantages: time buffers, Disadvantages: increase work in process inventory
Backward scheduling - an approach to scheduling that starts from desired due date and works backward. Advantages: decrease the work in process inventory; Disadvantages: no time buffers.
Today
Due Date B
Forward Scheduling E
Backward Scheduling

13. Shop Loading
The allocation of jobs to work centers is called shop loading
Loading methods :
Infinite loading - It does not take into consideration the limited capacity of the facility. Scheduling with unlimited capacity
Finite loading – assigns jobs to work centers without regard to capacity limitations. Scheduling with limited capacity
INFINITE LOADING (without regard for capacity)
Capacity
Time period 6 5 1 2 3 4
under
over

14. Shop loading Finite loading - scheduling with limited capacity –
It takes into considaration the limited capacity of each work center.
FINITE LOADING (never to exceed capacity)
Capacity
Time perid 6 5 1 2 3 4

15. Infinite loading
Planned orders to relise emitted by MRP system: 1,2,3,4,5.
Completion due date.: Orders1 and 4 – end of period 4.
Orders 2,3,5 – end of period 5
Start due date: Order.1 & 2 – beginning of period 1., Order.3 & 4 – b. period 2. Order 5 – b. period 3. 2 1 3 4 5
Order 40
Period 80
Work station load
(normal hours)
Load calculation:
Setup time + (n x tj)
E.g. order 1:
Setup = 1 h
Volume = 100 unites
Unit time = 0,4 h
Load = x 0,4 = 41 h

16. Finite loading 3 Orders planned to execution in week X (one week = 40 hours)
Turning [h]
Milling [h]
Driling [h] 1 8 12 2 4 3
Move time: 2 h.
Orders execution sequense (1,3,2)
determined with help of critical ratio
Machine
1 Day 8h
2 Day
16h
3 Day
24h
4 Day
32h
5 Day
40h
Lathe 1 3 2
Mill
Drill 1
Load
of Lathe [h] 8 2 3 4 5
Day 6
Capacity

17. Sequencing
Gantt Chart - at the same time assign the operations to machines and define the sequence
Gantt Chart - based on forward scheduling principles
Example:
Order
Operation 1
[h]
Operation 2
Operation3 A
Lathe 3
Drill 2
Mill 4 B C D 5
Delay and move time between machines 6 h.
Order Completion due date A B C D
Machine 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Lathe
OrderA Oper1
Order C Oper1
interval
Order D Oper 2
Mill
Order B Oper 1
Order C Oper 2
Order A Oper 3
Drill
Order D Oper 1
Order A Oper2
Order B Oper 2
Order C Oper 3
sequencing
sequencing

18. Sequencing Jobs In Work Centers Priority Rules for Dispatching Jobs
Scheduling - provides a basis for assigning jobs to work centers
Loading - is a capacity-control technique that highlights overloads and underloads
Sequencing - specifies the order in which jobs should be done at each work center.
Priority rules - determine the sequence of jobs in process-oriented facilities
First Come, First Served - FCFS. Job that enters the work center first has first pririty
Shortest processing time (SPT). Job with the shortest processing time is first executed
Longest processing time (LPT). Job with the longest processing time is first executed
Earliest due date (EDD). Job which is due first should be started first
Total slack (S). Job with the least total slack (buffor time) is done first
Random selection (RS). Random selected job is first executed .
Critical Ratio (CR). Job with the lowest critical ratio is done first

19. Critical Ratio Due date – Today’s date CR =
The critical – ratio (CR) is the rule that considers both due date and processing time .
Due date – Today’s date
CR =
Total processing time remaining
The job with the lowest CR is scheduled next.
CR = 1 – the order job has time to be completed on time
CR < 1 – the order job is delayed (it is already past due)
CR > 1 – the order job has time buffer
The CR rule is dynamic. The job’s critical ratio will change over time. The critical ratio must be constantly updated

20. Input-Output Control
Many firms have difficulty in scheduling because they overload the production processes. This often occurs because they do not know actual performance in the work centers. Effective scheduling depends on matching the schedule to performance in the work centers. Lack of knowledge about capacity and performance causes increasing in lead times.
Input-Output Control is a technique that allows operations personnel to manage facility work flows.
If the work is arriving faster than it is being processed, we are overloading the facility and a backlog develops. Overloading causes crowding in the facility, leading to inefficiencies and quality problems.
If the work is arriving at a slower rate than jobs are being performed, we are underloading the facility and the work center may run out of work. Underloading the facility results in idle capacity and wasted resources

21. Input-Output Control Example: (work Past Future Period 1 2 3 4 5 6
Planned Input [h] 50 56 48
Actual Input [h] 54 52
Planned output [h]
Actual output [h]
Planned load [h]
152
156
154
Actual load [h]
160

22. PRODUCTION ACTIVITY CONTROL SYSTEM
Production Activity Control system modules:
SCHEDULING - to develop a plan (schedule) based on current knowledge and data which will ensure all the production requirements are fulfilled
DISPACHING - to implement the schedule taking into account the current status of the production system
MONITORING – to monitor the status of vital components in the production system during the dispatching activity
Devices, machines, production process
MASTER PRODUCTION SCHEDULING
MATERIAL PRODUCTION SCHEDULING
CAPACITY PLANNING
Planned orders
Data collection
Instructions
Schedules
SCHEDULING
MONITORING
DISPACHING
PAC system

23. A Production Activity Control System Should
Schedule incoming orders without violating capacity constraints of individual work centers
Check availability of tools and materials before releasing an order to a department
Establish due dates for each job and check progress against need dates and order lead times
Check work in progress as jobs move through the shop
Provide feedback on plant and production activities
Provide work efficiency statistics and monitor operator times for payroll and labor distribution analyses

24. Order Release Begins Shop Loading
Release Order 1 2 3
Gross Requirements
Yes
Scheduled Receipts
100
Priority & Capacity OK?
Available
Net Requirements
Planned Order Rec. No
100
Hold Release
Planned Order Rel.

25. Johnson’s Rule – Johnson’s Algorithms
Used to sequence n jobs through 2 machines in the same order
Jobs (n = 3)
Saw
Drill
Job A
Job B
Job C

26. Sequencing Jobs on Two Machines
Job I
Machine 1
Machine 2
Cumulated Lead Time 15 hours
Sequence I, II
Job II
Sequence II, I
Machine 1
Machine 2
Cumuleted Lead Time 12 hours
The sequance of jobs has impact on total processing time (lead time) of the jobs

27. Johnson’s rule for sequencing n jobs (orders) on two machines
Johnson’s rule can be used to minimize the total processing time by sequencing a group of jobs on two machines . All jobs must followed the same sequence through the two machines
Start
Select the shortest job time in m1 or m2
List all job times for m1 and m2
Is it in m1?
Assign it as early as possible to m1
Assign it as late as possible to m1
Delete the job assigned from the list
Are all jobs assigned
Stop No
Yes

28. Johnson’s rule for sequencing n jobs on two machines
Work processing time for five jobs (in hours)
Job
Machine 1
(drill)
Machine 2
(lathe) 1 5 2 3 6 8 4 10 7 12 2 3 4 7
Initial jobs sequence: ,2,3,4,5
Optimal jobs sequence:
Lead time = 45h 2, 5, 4, 3, 1
Lead time = 35h