Various types of Operations Scheduling are:
1. Forward operations scheduling –
a. Classified on the basis of the time.
b. All the activities are scheduled from the date of the planned order release.
c. First task of the job is scheduled.
d. Its subsequent task is scheduled on the scheduled completion of the first task.
e. Like this, accordingly all the tasks of the job are scheduled.

2. Backward operations scheduling –
a. Also classified on the basis of the time.
b. Activities are scheduled from the date or the planned receipt date.
c. The last activity is scheduled first.
d. Time of the start of the last task is considered as the time for the start of the previous activity.

Methods used for the operations scheduling
1. Johnson’s two machine algorithm
a. Very effective when the operations sequencing has two machines and the processing time depends on the sequence in which the jobs are loaded.
b. Also used when the company involves a backlog of the orders.
c. Is a very simple process.
d. Also a time saving process.
e. Helps in the determination of the optimal job sequence.

2. Index method
a. Used for the purpose of the loading and also for allocating the different jobs to the different machines.
b. Generally orders are assigned on the basis of the “first come first assigned” method.
c. But does not provide optimum loading.

3. Critical path analysis
a. Helps in the determination of the scheduling of the activities of the projects.
b. Reveals inter – relationships between the different activities of the project.
c. Reflects the uncertainty in the durations estimated for the various activities.

4. Critical ratio scheduling
a. Helps in the establishment and the maintenance of the priorities among the jobs in a factory.
b. Concept of “critical ratios” is used widely.
c. Helps in the expedition of the functions of the PPC.

1. Performance standards –
a. First and the foremost need of the operations scheduling.
b. Helps the scheduler to find out the machine capacity in order to assign the required machine hours and the man – hours for the various activities.
c. The performance standards play a very important role in the good operations scheduling and this is always possible if the time study or the industrial engineering department exists in the plant.
d. The performance standards for such repetitive jobs are available.
e. And for the new jobs, they can be determined from the tables of the synthetic standards prepared by the department.

2. Unit of the measurement –
a. Means the unit in which the loading and also the scheduling is to be extended.
b. The most commonly used units of measurement in the engineering companies are the man – hours or the machine – hours.

3. Unit of the loading and the scheduling –
a. Means the duration for which the loading and the scheduling should be done.
b. The unit of the loading and the scheduling – scheduled start and the finishing timings – are mainly dependent on the scheduling needs of the company.
c. Scheduling should be done on the daily basis if the company makes promises in days.

4. Effective capacity per work centre –
a. Means the effective hours that can be used for the production on the machine or on the work centre in a week or in a month.
b. Theoretical capacity is equal to the number of the normal working hours of that machine.
c. Some interruptions may occur during the process and some of these interruptions can be summarized as follows –
i. Power failure.
ii. Rework.
iii. Waiting for transport.
iv. Preventive maintenance.
v. Waiting for the inspection.
vi. Tool try – out, jigs and the fixture try – outs.
vii. Operatives’ trade test.
viii. Operators involved in some other activities like the functions, celebrations etc. – leaving the production operations aside.
ix. Machine used for the technical studies.
x. Operator left the work place for the official decision.
xi. Machine breakdown – may be technical or mechanical in the nature.
xii. Operator absence.
xiii. Breakage in the tool.
xiv. Operator training time.
xv. Starting late.
xvi. Early close.
xvii. Over – time.
xviii. Incentive payment collection.

5. Extent of the rush orders –
a. When considering the scheduling process, the rush – orders play a very conclusive role.
b. Never a machine should be subjected to 100 % effective capacity, simply because of the reason that if any rush order comes in, and then the scheduling has to be changed.
c. The various methods used in the accommodation of the rush orders can be summarized as follows –
i. Leaving some capacity unscheduled on each machine per period.
ii. Leaving some in scheduled capacity between the two scheduled jobs.

6. Overlapping of the operations –
a. Means running of a job simultaneously on more than one machine.
b. Occurs in the jobs which involve two or more operations.
c. Reduces the manufacturing cycle time.
d. Reduces the delivery period to the customer.

7. Loading charts
a. These charts specify the work that is to be carried out in each section or the department of the company during the period under the review.
b. Helps in knowing the accumulated load at a given time for a given machine.
c. Helps in the identification of the periods that are available for the allocation in the future to orders needing this machine.

Objectives of the Operations Scheduling –
1. Making efficient use of the labour.
2. Making best possible use of the equipments that are available for the use.
3. Increasing the profit.
4. Increasing the output.
5. Improving the service level.
6. Maximizing the delivery performance i.e. meeting the delivery dates.
7. Minimizing the inventory.
8. Reducing the manufacturing time.
9. Minimizing the production costs.
10. Minimizing the worker costs.

Functions of the operations scheduling –
1. Allocation of the resources.
2. Shop floor control.
3. Making maximum use of the plant at minimum possible cost.
4. Ensure that the needs of the manpower are optimum.
5. Determination of the sequence of the jobs.
6. Specifying the start and the end time for each job (actively scheduled).
7. Getting quick feedback from the shops regarding the delays and the various interruptions.
8. Possess up – to – date information for the availability of the materials, expected delivery dates etc.
9. Possess up – to – date data on the machine regarding its breakdown, servicing etc.
10. Keep itself abreast of the hiring, dismissals, holidays etc. of the work force.

Introduction
In the operations management or the production management, this technique of operations scheduling forms a very important part and acts as the back – bone for the performance of the manufacturing or the service organizations. With the help of the operations scheduling, two very important factors or the aspects of the resources within an organization that can be pertained are as follows –

1. Allocating the resources within an organization.
2. Setting up the time – table.

In today’s competitive world, the orders that are placed either from the side of the customer or from the side of the assembly benches – are to be completed on or before the contracted or the promised date. For fulfilling this, operations scheduling plays a very critical and an essential role and completely ensures that these dates are met.

Operations scheduling helps in the confirmation or the revision of the tentative delivery date that has been promised in the original quotation. Sometimes during the operations scheduling of the work order, it may be discovered that the delivery date originally and tentatively promised cannot be met. All this may be due to the several problems like the materials that are required may not be available at that particular time or may not be available immediately. This problem can also occur due to the increased plant loading while the customer is deciding whether or not to award the quoted job to this company.

It has been observed that the operations scheduling has a direct affect on the effectiveness of the production function and this relation was actually explained by Vollman.

According to Vollman, “The priority planning and the shop floor control and the scheduling elements ultimately determine the performance of the production system.”

If the operations scheduling is carried out in an efficient manner, then there occurs a considerable improvement in the performance in the delivery. Also helps in the achievement of the goals that have been set by the company. Efficient operations scheduling playa a very critical part in the reduction of the production lead times.

1. A planning horizon is considered from about 3 to 18 months, with the periodic updating.
2. Aggregate product demand, stated in the common terms is observed.
3. Aggregate resource quantities, stated in the common terms are observed.
4. Influence both the supply and the demand by adjusting the production rates, workforce levels, the inventory levels etc., but the facilities cannot be expanded.

Aggregate planning strategies

1. Active strategy –
• Tries to control the fluctuations, which are in the demand by focusing on the demand management.
• Use the pricing strategies.
• Make use of the methods like the advertising and the promotion.
• Do not meet demand.
• Develop counter – cyclical products.
• Request the customers to back order or advance order.

2. Passive strategy –
• Also called as the reactive strategy.
• Tries to control the fluctuations in demand by focusing on the supply and capacity management.
• Vary size work force by hiring or lay – offs.
• Vary utilization of the labour and also of the equipment through the overtime or the idle time.
• Build or draw from the inventory.
• Sub – contract production.
• Negotiate co – operative arrangements with the other firms.
• Allow the back – logs, back orders and/or stock outs.

3. Mixed strategy –
• Joins or combines the elements of both of the active strategy as well as the passive or the reactive strategy.
• Firms will usually use some combination of the two.