Production control

Production planning and control1. Production forecasting/ planning2. Production Control:The importance of control functions and procedures will vary from factory to factory. This variation systems from differences in• The degree of control required• The control organization• Factory management• Market served• The manufacturing process.• The product complexity.

Factors determining control procedures

Control procedures are determined by several conditioning factors:• Varied or repetitive character of operations.• Nature of manufacturing processes.• Magnitude of operations.

Varied and Repetitive Operation

In general variety of operations complicates the problem of planning and control, where as repetitive operations, since they reduce variety tend to simplify the problem.In practice, there are all sorts of variant between these two extremes. These may be represented by the continuous production of a single standardized product on the one hand and the completely special order business on the other.

Some of the principle variants are

• Manufacturing to order, which may or may not be repeated at regular intervals

• Manufacturing for stock, where the product is made up of parts but the processes are not optional. Custom orders may be intermingled.

• Factors tending to a complex control system are: a) Number of ultimate parts in the product. B) Number of different operations on each part. C) Extent to which processes are dependent, that is processes which

cannot to be performed until previous operations have been completed.• Variations in capacity of machines for different classes of work. Example

speed of machines varies according to the nature of the material being work on.

• Degree to which subassembly exists.• Occurrence of customer orders containing specific delivery dates.• Receipt of orders for many small lots.

Factors tending to simplicity of planning and control are:

• Degree to which repetitive work occurs, that is, when the same work is done over and over again in the same way, preferably in cycles.

• Absence of special dates for special items, as when everything is made for stock.

• Fixed capacity of machines or processes.• Invariable method of operation of machines or processes• Absence of discreet parts and assembly• Completely balanced production in which capacity of

every process is strictly proportional to flow of work.

Nature of Manufacturing• Control is at a minimum where a single homogeneous product is

treated by a fixed sequence of processes in a continuous flow. Eg: Coke Cola bottles or underwear.

• Repetitive operations in factories making many products at the same time. Here a great variety of materials are used in many ways and for many purposes. Sometimes the situation is made even more difficult when custom orders and manufacturing for stock are intermingled. Less accurate planning is possible when manufacturing for stock.

Little forecasting and no definite scheduling is possible with the raw material situation can be surveyed in light of probable demands.

Magnitude of operations

• Scale of operations has an important bearing on the nature of the problem.

• The degree to which the performance of any activity must be decentralized depends upon the scope of operations and the convenience of their location in larger factories, activities associated with warehousing, processing operations and custody of finished goods must of necessity be carried on in numerous locations.

Routing

• Routing really begins at the determination of the sequence of operations. Methods of work and machine analysis are preliminary to it. It can be performed properly only by people who are thoroughly familiar with the character of the work to be done and with the resources available for doing it.

Factors involved in routing are:• A study of product to determine the possible methods of processing and to

select the best method.• A study of methods to determine what if any, special equipment is necessary to

carry them out.• Any analysis of the capacity of the machines and equipment available for the

process.• The establishment of the sequence of operations.• A decision as to speeds at which operations shall be performed. • The determination of S.A.H. required for each operation.• The preparation of operational breakdowns listing the sequence of operations. • Grouping operational breakdown into subassemblies and major assemblies to

insure that the components will be started in process at such times as will insure their being completed simultaneously.

• The preparation of specifications sheets to ensure quality meets specifications.

Preparation for operational breakdowns and production orders.

Data usually included on an operational breakdown and production order is as follows:• Number and other identification of product group• Style number• Number of pieces to be made• If put through in lots, the number in each lot.Operational data including:• List of operation on the product• Departments in which the work is to be done • Machine to be used for each operation• Fixed sequence in any of the operations.• Standard allowed hours per piece

Loading and Scheduling

Loading decisions much be reached on:• The units and required accuracy of loading data.• The use of graphic control-charts or boards and the form

they should take.• The design of control records,• Duplicating requirements • Computer programs to sort and tabulate data• Filing procedures.• The manner in which communication should be handled

Loading and Scheduling Procedures

• Intermittent manufacture• Custom Order Manufacture• Production for Stock• Continuous Manufacture

Intermittent manufacture• Scheduling within the order or product. It is necessary to

determine relative dates at which each process on each part or lot shall be started and finished

• Scheduling of orderin relation to other orders. In custom work this will depend on the delivery date of the order; in stock manufacturing, on the relative dates at which each component should be completed for stock.

• Scheduling to machines or machine loading. With the required completion date for an order or lot at hand, reference to a schedule of relative processing dates will show when each process should be started.

Customer Order Manufacture

Scheduling often becomes a compromise between the time at which a job should be done and the day at which it can be done in view of previous commitments. Where work is put through comparatively large lots and where the manufacturing program is made up months ahead, scheduling in absence of rush orders is a much easier operation.

Production for Stock

• Even though production still moves in lots through separate process departments, control problems are simplified when production for stock becomes possible. This is particularly, true where inventories of finished products can be built up. The same effect occurs on a more limited scale when items can be stocked in a partially finished state. Finished inventories sharply reduce the interval between the receipt of an order and its delivery to the customer.

Continuous Manufacture

• Loading and scheduling procedures, for continuous manufacture are simpler than those required for intermittent manufacture. On the other hand the careful planning required to coordinate production with sales, inventory levels, purchasing, engineering and financing operations becomes extremely important because of the high and continuous rate of production.

Costs and Benefits of Production Control

“In any manufacturing enterprise, someone must perform the various functions of production control; whether it is done by a group of specialists or whether is done by the superintendents, foremen and workmen is a matter for each organization to decide, after a consideration of the costs of each method as related to the results obtained.”

Benefits:The customers:• Increased productivity• Better values• On time deliveriesThe producers:• Adequate wages• Stable employment• Job security• Improved working conditions• Increased personal satisfaction• Security of investment• Adequacy of return

The community:• Economic and social stabilityThe nation• Security• prosperity

“Better schedules mean better use of men and machine for higher efficiency…. Set-up costs cut by (proper) scheduling… In-process inventory minimized by (proper) scheduling.”