pom ch-15

PRODUCTION AND OPERATIONS

MANAGEMENT

Chapter 15SHOP FLOOR PLANNING AND

CONTROL

Himalaya Publishing HouseProduction and Operations ManagementBy K. Aswathappa & K. Shridhara Bhat

Chapter 15Shop Floor Planning and

Control

Shop floor planning and control:

• Principles and techniques required to plan, schedule, control and evaluate the effectiveness of production operations.

Concerns of Production Activity Control



Control

Production activity control is concerned with:• Priority Control• Capacity Control.

• Objectives of Production Activity Control1. To know the current status of the job2. To determine what should be the next job to be processed and in which

work centre.3. To maximize operational efficiency4. To minimize work-in-progress inventory.5. To minimize set-up costs.6. Minimize set-up cost7. To maintain control of operations by monitoring job status and lead

times, measuring progress and indicate corrective action when necessary



Control

Operations Planning and SchedulingThe various terms used in operations planning and scheduling are described briefly.1. Loading: Assignment of jobs to various work centres or

machines for future processing.2. Sequencing: The process of determining the sequence of

processing of all jobs at each centre or machine.3. Detailed Scheduling4. Expediting: The special effort or action needed to keep the job

moving through , the production facility on time as per the detailed schedule.

5. Input-output control: Managing work flow and queues at work centres.



Control

The Operations Planning and Scheduling System



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Elements of Scheduling

i. Demand forecasts/customer’s firm ordersii. Aggregate scheduling iii. Production plan iv. Master production schedulev. Priority planningvi. Capacity planningvii. Facility loading or machine loadingviii. Evaluation of workloadix. Sequencing



Control

Scheduling and Shop Floor Decisions in Process - Focused Production System



Control

Scheduling Techniques for Job Shop1. Forward scheduling 2. Backward scheduling• Forward Scheduling: From some point in time• Back ward Scheduling: Scheduling by working

backwards from the due dates.



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Stage in Scheduling

1. Loading 2. Dispatching1. Loading: The assignment of jobs to processing centers.2. Dispatching: Sequencing and selecting jobs waiting at a

Work Center when Capacity becomes available.a. Finite loading: Jobs are assigned to work centers

taking into account the capacity of the work centre and job processing time.

b. Infinite loading: Jobs are assigned to work centers without regard to the capacity of the work centre.



Control

Load Charts and Machine Loading Charts

Load chart: A Gantt chart that shows the loading and idle times for a group of machines or Work centers.

Gantt chart: Chart used as visual aid for loading and scheduling purposes.



Control

Priority Sequencing

Priority Sequencing: Determining the priority for all the jobs waiting in a queue by applying priority sequencing rules.



ControlSingle-Criterion Priority Sequencing Rules

Some single-criterion priority sequencing rules are:1. First come first served (FCFS)2. Shortest processing time (SPT) or shortest - operation time (SOT) or

minimum processing time (MINPRT).3. Longest processing time (LPT) or longest - operation time (LOT)4. Least slack job (LS) first or minimum slack (MIN SLACK) job first.5. Earliest due date (EDD) job first6. Truncated shortest processing job first (TSPT)7. Preferred customer order (PCO) first8. Random selection (RS)9. COVERT (Cost over time)10. Least change-over cost.



Control

Dynamic Sequencing Rules (Combined Criteria Rules)

a. Dynamic slack (DS) rule

b. Dynamic slack per remaining operation (DS/RO) rule.

c. Critical ratio (CR) rule.• Scheduling ‘n’ jobs on ‘m’ Machines (m = 2 or 3)



Control

Johnson’s Rule or Algorithm

Johnson’s Rule: Technique for minimizing cycle time for a group of jobs to be processed on two machines or at two work-centers.



Control

Scheduling Product Focused Systems

Two techniques used in resolving scheduling-related problems in product-focused production systems are:

i. Batch scheduling

ii. Scheduling and controlling production for delivering schedules.



Control

Economic Batch Quantity (EBQ) or Economic Run Length (ERL)

a. Set-up costs i.e.,, costs/unit which decrease with batch size.

b. Inventory carrying cost which increases with batch size.

Case 1 : Instantaneous supply with no simultaneous consumption:



Control



Control

• Case 2 : Non-instantaneous

supply with simultaneous consumption

• Determination of EBQ



Control

Scheduling and Controlling Production for Delivery Schedules - Line of Balance

(LOB) Method

Line-of -Balance Technique: A technique used in production scheduling and control to determine at a review date, not only how many of an item should have been completed by that date, but also how many should have passed through the up-stream operation stages by that time, so as to ensure the completion of the required delivery schedule.



Control

Line Balancing

Line Balancing: Arranging a production line so that there is an even flow of production from one work station to the next, so that there are no delays at any work station that will leave the next work station with idle time.



Control

Line Balancing Procedure in Assembly Layouts

i. Step 1 : Determine what tasks must be performed to complete one unit of a finished product and the sequence in which the tasks must be performed. Draw the precedence diagram.

ii. Step 2 : Estimate the task time (amount of time it takes a worker to perform each task).

iii. Step 3 : Determine the cycle time (the amount of time that would elapse between products coming off the end of the assembly line if the desired hourly production were being produced.)

iv. Step 4 : Assign each task to a worker and balance the assembly line. This process results in determining the scope of each worker’s job or which tasks that he or she will perform.



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• Determination of cycle time (CT)



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Determination of the Ideal or Theoretical Minimum Number of

Workers Required in the Line



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Balancing Efficiency

• An efficient line balancing will minimize the amount of idle time.

• The balance efficiency can be calculated as:



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Line Balancing Methods

The various line balancing methods or techniques used are:

1. Heuristic methods

2. Linear Programming

3. Dynamic Programming

4. Computerised line-balancing

pom ch-15

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