Production Planning and Control: A Project Report

Planning Phase:

Forecasting:

1. Forecasting means estimation of type, quantity and quality of future work e.g., sales etc.

2. The survival of a manufacturing enterprise depends on its ability to assess, with reasonable accuracy, the market trends several years ahead.

3. Forecasters will be able to make use of sales trends, but these must be considered in the light of expected introduction of new materials, fashion changes, policies of competitors, unseasonable weather, threat of war and the general economic situation expected in the country and foreign markets. These circumstances and others necessitate changes in sales forecast from time to time during the forecast period.

4. Forecast represents a commitment on the part of the sales department and each of its divisions of expected sales. It becomes a goal against which the effectiveness of the sales department will be measured.

5. Forecasting plays a crucial role in the development of plans for the future.

6. Sales budget (estimate) forms the basis for manufacturing budget. It is the sales forecast which enables to determine production quantities, labour, equipment and raw material requirement.

7. A sales forecast should be;

a. Accurate,

b. Simple and easy to understand, and

c. Economical.

Purpose (or Need) of Sales Forecasting:

Sales forecasting is essential because:

(i) It determines the volume of production and the production rate.

(ii) It forms basis for production budget [step (6) above], labour budget, material budget, etc.

(iii) It suggests the need for plant expansion.

(iv) It emphasizes the need for product research development.

(v) It suggests the need for changes in production methods.

(vi) It helps establishing pricing policies.

(vii) It helps deciding the extent of advertising, product distribution, etc.

Sales forecasting, Basic elements of:

Forecasting means predicting future events by the best possible means.

ii. In any sales forecasting analysis, there are four basic elements of economic data that should be used:

1. Trends.

2. Cycles.

3. Seasonal variations.

4. Irregular variations.

Trends are the long term, long range movements of a series of economic data. They have little relationship to the month-to-month changes that take place, and they manifest their direction. Cycles are of shorter duration and they are usually featured by alternate periods of expansion and contraction.

Seasonal variations occur within a certain period of year and recur at about the same time and to approximately the same extent from year to year. Irregular variations are the result of unforeseen or non-recurring events that have an economic influence. A strike in a key industry might cause an irregular variation.

Technological Forecasting:

Since the pace of technological change is so great, and since new products and processes may be keys to a company’s future plans, an increasing number of companies are emphasizing regular and complete technological forecasts affecting their industry. Technical forecasting may be defined as-forecasting the future technology that may affect the operations of an enterprise.

Those companies which have gone far in developing planning premises from their technological forecasts have tended to be high-technology enterprises. What has been done in these instances is to encourage members of their technical staffs to be alert to future developments; to arrange frequent contacts of suppliers customers with development staffs; to think in terms of the impact of current scientific developments on the future state of technology; and to develop orderly forecasts of how these developments affect the company’s products, processes or markets.

One of the attempts to make technological forecasting more accurate and meaningful is the use of Delphi technique. Another method used to forecast the state of technology is opportunity-oriented. It looks at the future and raises the question of whether a certain product may be made obsolete by a new development – and, if so, what development-or whether there is any technological break­through that might be expected which would solve a problem seen to exist in the development of a certain product.

For example, the opportunity-oriented forecast might look at the possible development of an atomic power plant for an automobile and ask whether certain known limitation will probably be solved and when. Or one might forecast when economic desalination of sea-water will occur. Another approach has been referred to as the goal-oriented forecast.

In this case, a decision is made to reach a certain goal, the technological needs for accomplishing it are identified, and analysis is made as to when, and perhaps how, these might be accomplished. Thus, after a decision was made to put a man on the Moon by 1970, the technological requirements of so doing were identified, and time and resource estimates were made as to how to achieve the target.

Tool Control:

Concept:

Tool control implies:

(1) Determining tool requirements,

(2) Procuring necessary tools, and

(3) Controlling/maintaining tools once they have been procured.

A tool or process planner must calculate tool requirements prior to the time of production to ensure that proper tools will be available when needed. Lost time resulting from incomplete tool planning can be expensive as well as causing work to delay. In order to facilitate tool control and to limit the investment in tool inventory, it is important to standardize wherever possible all the tools within an organisation.

Need for:

Tool control is very important to ensure:

(1) Against loss through theft or negligence and production delays through misplacement or non­-availability of tools.

(2) That the investment in tool inventories is minimized consistent with proper tool availability.

Procedure of:

Two methods are commonly used to control the issue and receipt of tools to and from the workers:

(1) The Brass Ring System:

Brass rings with worker’s identification number marked on them are issued to every worker. When he draws a tool from the crib, he gives one of his rings to the attendant and the ring is hung on a peg at the tool bin. When the worker returns the tool, the ring is returned to him.

This method is very simple and can be used where the workers are not much educated. However it invites dishonesty because of the ease with which counterfeit rings can be made. The method also does not provide any means of determining tool usage.

(2) The McCaskey System:

a. This system is based upon 3-part carbon backed form, (Fig. 7.16). The worker fills it out and presents it to the tool crib attendant when he wishes to withdraw a tool. One copy of the form is maintained under a clip with the worker’s name or his clock number and a second copy under a clip of the tool number. The third copy is given to the worker for identification of the tool.

b. The copy filed under tool number provides ready reference that, particular tool is not available when a later request is made for it.

c. Periodic checks of the slips under the worker’s clip will indicate if tools are being hoarded or held for an excessively long time.

d. When the tool is returned along with the third copy of the form which the worker had kept for his information (identification of tool), the copy under the worker’s clip is removed and given to the worker.

The copy under the tool number clip is removed and placed behind the tool inventory card at the back of each clip. Every month, the slips behind the card are counted to indicate tool usage and the individual slip thrown away.

e. This system is widely used in manufacturing establishments because of its excellent control features.

Loading:

Loading means assignment of work to manpower, machinery etc., without specifying when the work is to be done. Loading results in a tabulated list or chart showing the planned utilization of the machines or work stations in the plant (refer Fig. 7.17). The objective of the loading function is to maintain an up-to-date picture of the available capacity in the plant. Loading can be defined as the study of the relationship between load and capacity at the places where work is done.

The information provided by loading is used:

(1) To ensure the efficient utilisation of the plant and labour in a factory,

(2) To help in the setting of reliable delivery promises,

(3) And to assist in the forward planning of the purchase of new plant.

Load 1 (v) To assign work to the capacity available at particular work centres. 2(n). The total of the standard times of all the work assigned to a given work center plus allowances for machine idle time, ancillary time and down time; and for substandard performance. Capacity can be defined as the time available for work at work centres expressed in machine hours or in man-hours.

Aims of loading:

(1) To check the feasibility of production programmes.

(2) To assist in the efficient planning of new work.

(3) To assist in balancing the plant to the existing load.

(4) To assist in the fixing of reliable delivery promises.

A load chart (Fig. 7.17) shows the productive capacity that has been sold and at the same time the available productive capacity. Load chart may be prepared for each machine or a group of machines available in the factory. Load charts, as such, are not too common because loading function is usually combined with scheduling and only one set of charts is maintained: The schedule charts.

Scheduling and Control of Production:

Once the planning (work) to meet sales is complete and a set of decisions have been formulated using Graphical or Linear programming methods, the next step is the imple­mentation of the decisions through detailed plans and schedules. Schedules are made for the use of facilities like equipment and manpower.

Scheduling and Control of production focus attention on the following:

(a) Knowing the total overall production targets -how to determine the amount of each product to be manufactured if there are products of different types and sizes?

(b) How to decide about and deploy work force (different types of workers and kinds of skills) and equipment to achieve the target production rate?

(c) How to determine individual work assignments?

(d) What should be the information system to feed back quickly and accurately the actual output duly compared with the scheduled one?

Scheduling and Control of production have one stage in between them, which is known as dispatching. In general, first of all the order is scheduled, then it is dispatched for necessary operation (on the raw material) and lastly the progress of the order is tracked, to be certain that the schedule is being met. This (last) phase of tracking the progress of an order and making corrections (if necessary) is known as control of production.

Routing:

Routing lays down the flow of work in the plant. It determines what work is to be done and where and how it will be done. Taking from raw material to the finished product, routing decides the path and sequence of operations to be performed on the job from one machine to another. The purpose is to establish the optimum sequence of operations. Routing is related to considerations of layout, temporary storage of in-process inventory and material handling.

Routing in continuous industries does not present any problem because of the product type of layout, where the equipment is laid as per the sequence of operations required to be performed on the components (from raw material to the finished products).

In open job shops, since, every time the job is new, though operation sheets (sometimes) may serve the purpose, but the route sheets will have to be revised and this involves a greater amount of work and expertise.

Routing Procedure:

Various procedural steps are as follows:

(a) The finished product is analysed from the manufacturing standpoint in order to decide how many components can be made in the plant and how many others will be purchased (Make/Buy decision) from outside through vendors, by subcontracting, etc. Make/buy decision depends upon the work load in the plant, availability of equipment and personnel to manufacture all components, and the economy associated with making all components within the plant itself.

(b) A parts list and a bill of materials is prepared showing name of the part, quantity, material specifications, amount of materials required, etc. The necessary materials, thus, can be procured.

(c) From production standards-machine capacities, machine characteristics and the operations which must be performed at each stage of manufacture are established and listed in proper sequence on an operation and route sheet, (See fig. 7.27). The place where these operations will be performed is also decided.

Actually, operation sheet and route sheet are separate. An operation sheet shows everything about the operations, i.e., operation description, their sequence, type of machinery, tools, set up and operation times, whereas a route sheet besides listing the sequence of operations and relation between operation and machine, also details the section (department) and the machines to whom the work will flow. First two columns of Fig. 7.27 are mainly those of route sheet which show the manufacturing route for given component.

The difference between an operation sheet and a route sheet is that an operation sheet remains same for the components if the order is repeated but the route sheet may have to be revised if certain machines are already committed to other orders (jobs) on hand. Except this small difference, both the sheets contain practically the same information and thus are generally combined into one sheet known as ‘operation and route sheet’.

(d) The next step is to determine the lot size or the number of components to be manufactured in one lot or batch. In the case of an order from a particular customer, it is generally equal to a number within 10% of the order quantity. In other cases the principle of economic batch quantity can be applied to determine the batch size.

(e) Standard scrap factors (single or cumulative) and the places (i.e., after a particular operation or assembly) where scrap is very likely to occur are identified. The actual scrap in each batch can be recorded on the control chart. Causes for points out of control limits are explored and corrected. The variables like workers, machinery and schedules may also be adjusted to minimize scrap.

(f) The cost of the component is analysed and estimated through the information obtained in steps (a) to (e) above. The cost consists of material and labour charges, and other specific and general indirect expenses.

Scheduling:

In brief, scheduling means -when and in what sequence the work will be done. It involves deciding as to when the work will start and in a certain duration of time how much work will be finished. Scheduling deals with orders and machines, i.e., it determines which order will be taken up on which machine and in which department by which operator. While doing so, the aim is to schedule as large amount of work as the plant facilities can conveniently handle by maintaining a free flow of material along the production line.

Scheduling may be called the time phase of Loading. Loading means the assignment of task or work to a facility whereas scheduling includes in addition, the specification of time and sequence in which the order/work will be taken up.

A production schedule is similar to a railway time table and shows which machine is doing what and when. A production schedule is a statement of target Cates for all orders or operations in hand and reveals their starting and finishing dates. Scheduling finalises the planning phase of Production Planning and Control System.

Factors Affecting Scheduling:

The following factors affect production scheduling and are consi­dered before establishing the scheduling plan:

(a) External Factors:

1. Customer’s demand,

2. Customer’s delivery dates, and

3. Stock of goods already lying with the dealers and retailers.

(b) Internal Factors:

1. Stock of finished goods with the firm,

2. Time interval to process finished goods from raw material. In other words-how much time will be required to manufacture each component, subassembly and then assembly (i.e., the final product),

3. Availability of equipment and machinery; their total capacity and specifications,

4. Availability of materials; their quantity and specifications,

5. Availability of manpower (number, type and kind of skills),

6. Additional manufacturing facilities if required, and

7. Feasibility of economic production runs.

Scheduling Procedure and Techniques:

Scheduling normally starts with the Master Schedule. Figure 7.18 shows the master schedule for a foundry shop.

A master schedule resembles central office which possesses information about all the orders in hand. Master schedule, in Fig. 7.18, is a weekly breakdown of the production requirements. The total capacity in any week is of 100 hours of work in the foundry shop.

As the orders are received, depending upon their delivery dates (or priorities, if any) they are marked on the master schedule. When the shop capacity is full for the present week the newly acquired orders are carried over to the next week and so on. A master schedule is thus updated continuously, it depicts a running total of the production requirements and shows the work ahead-yet to be completed. Master schedule is actually the basis for all subsequent scheduling techniques.

A Master Schedule possesses the following advantages, disadvantages and applications:

Advantages:

1. It is simple and easy to understand,

2. It can be kept running (i.e., current),

3. It involves less cost to make it and maintain,

4. It can be maintained by non-technical staff, and

5. A certain percentage of total weekly capacity can be allocated for rush orders.

Disadvantages:

1. It provides only overall picture, and

2. It does not give detailed information.

Applications:

It finds applications:

1. In big firms, for the purpose of loading the entire plant,

2. In Research and Development organisations, and

3. For the overall planning in foundries, computer centres, repair shops, etc.

After framing the overall picture of production requirements through a Master Schedule chart, the detailed schedules are thought of and made for each component and subassemblies so that all parts are available at the time of assembly. There are a number of visual aids and techniques, both in the form of conventional charts and commercially available boards, which aid in detailed scheduling.

The technique to be employed for scheduling purposes depends upon the type of production (intermittent or continu­ous), type and frequency of tasks, demand patterns, etc. A useful scheduling device normally portrays planned production, actual performance and their comparison. Actually, the Gantt Chart (refer Fig.-7.20) forms the basis of commonly used scheduling techniques.

Some of the techniques (besides master schedule) employed for Loading and Scheduling purposes are:

(a) Perpetual schedule

(b) Order schedule;

(c) Loading by schedule period;

(d) Commercial devices.

(a) Perpetual Scheduling:

Like master scheduling, it is also simple and easy to understand, is kept current, involves less costs and can be maintained by clerical staff. But, the information which it provides is very gross and at the same time it is not clear from the chart-when the work will take place.

Making of perpetual schedule involves two steps:

(i) Preparation of Load Analysis sheet from the orders in hand. Figure 7.19 shows a load analysis sheet.

(ii) The total load against each section is added up and knowing the weekly capacity of a section (department), the number of weeks load against each department is calculated and plotted on a Gantt load chart as shown in Fig. 7.20.

The shaded bars show the actual work load against each section.

Additional information, if any (regarding the work load), can be indicated by dotted line.

(b) Order Scheduling:

It is a most elaborate technique. Fig. 7.21 shows an order schedule chart. Time is marked horizontally and the vertical axis shows the particular facility (say a machine). The information required to generate an order schedule is, regarding the number of parts to be manufactured, name of the machines, their set-up times, total production time and the date of completion of the order.

The scheduling is started by placing the last operation at the date of completion and then working backwards, For example, if orders takes 3 days to complete and it is to be delivered to the customer on 7th of January, the work will be started on 5th of January.

Order schedule chart has the following advantages and limitations:

Advantages:

(1) It is very detailed.

(2) The earliest possible completion dates can be met.

Limitations:

(1) It is very costly.

(2) It requires accurate (production) time standards and good communication system.

(3) It is difficult to maintain effectively if there are many active orders.

(c) Loading by Schedule Period:

The task is broken into different operations which will be required to turn raw material into finished product. A Gantt type of chart (See Fig. 7.22) is employed for scheduling purposes. The rows, mark different facilities and each column denotes a time period (TP). There are as many time periods as the number of operations. The first operation is carried out in the time period-1, second operation in time period-2 and so on.

It is however not specified that, within the time period, when the operation will start and finish; but the operation is very much supposed to be completed during that particular time period. The shop supervisor does the detailed scheduling within the framework of the specified time period.

The shaded bars show the work ahead of each facility.

This type of scheduling involves a longer in-process (total) time because only one operation is to be performed in one time period. However, this makes it more flexible as an operation can be taken up at the most convenient time within the specified time period.

(c) Some of the Commercial Devices for Loading and Scheduling are:

(a) Produc-Trol Board,

(b) Sched-U-Graph,

(c) Board master,

(d) Magnetic boards, and

(e) Roll charts, etc.

(a) Produc-Trol Board.

Fig. 7.23 show a Produc-Trol board.

IRP: Index record panel.

TP: Tape pegs.

S: Strings.

PB: Peg board having two rows of holes for each pocket.

HKPP: Heavy craft paper pockets. Each machine is assigned a pocket. A card bearing information pertaining to the machine is inserted in the pocket.

ATP: It is a tape peg showing actual work load for each machine.

CP: It is a coloured peg (shown dotted) that gives special information; for example last week’s load.

VS: Vertical string showing today’s date and the work load position.

(b) Sched-U-Graph. It is shown in Fig. 7.24.:

OLF:

Overlapping flap. Every flap is projecting about 12 mm below (out) the previous one, and has bottom (12 mm) portion transparent. A card is made for each operation (to be done) on a machine. The card has written on it everything about a job.

The bottom (12 mm) of the card is coloured and the card is cut to a length depending upon the time the job will take on a particular machine. The black strips in Fig. 7.24 correspond to the coloured bottoms of the cards and indicate which machine will be busy during which period. The progress made against each order can also be shown by strips of other colours.

Manufacturing Schedule:

A master schedule is too general to permit adequate day-to-day planning by line supervision, and is usually unnecessary in a small organisation.

Weekly departmental manufacturing schedules supplement the master schedule and must be made to reflect immediate factors, some of which are:

(1) Tool downtime due to broken and worn tools,

(2) Equipment downtime for repair and maintenance,

(3) Shortages and defects in materials,

(4) Absenteeism and

(5) Cancellations and rush orders.

The weekly schedule should take advantage of the most economical setup sequence in a process where more than one part is produced on the same line. It is important to arrange the order of work on the weekly schedule, to minimize setup time. Sometimes much of the same tooling can be used for certain operations on parts A and C.

Part B, requiring a different setup on the same machine, should then follow part C rather than precede it. The operating supervisor can help greatly in working out these combinations. Successive master schedules are corrected from the variations reflected in the manufacturing schedules. Weekly manpower requirements are based on the manufacturing schedules and excessive fluctuations must be avoided.

Scheduling and the Computer:

Since Scheduling is the main process carried out in production control, it is worth to consider the relationship between the computer and scheduling. The computer is an extremely versatile tool which can be programmed to undertake almost any data processing task. In many types of industry, much of the data required for scheduling is relatively fixed in relation to time.

In this category can be included the data contained in parts lists, route cards and plant lists. Many of the data processing needs of production control use this type of data. Examples are, explosion to find parts requirements, implosion to find the requirement of common materials and loading to calculate forward loads on machines and direct workers.

For these types of data processing, the computer is ideal. Continuous data (such as store receipts, store issues, products dispatched etc.) is used by production control in the compilation of stock records, shortage lists and operations statistics. Computer, again, can do the actual data processing much more accurately and quickly than is possible manually.

Action Phase:

Dispatching:

Dispatch function executes planning function. It is concerned with getting the work started. Dispatching ensures that the plans are properly implemented. It is the physical handing over of a manufacturing order to the operating facility (a worker) through the release of orders and instructions in accordance with a previously developed plan of activity (time and sequence) established by the scheduling section of the production planning and control department.

Dispatcher transmits orders to the various shops. Dispatch function determines-by whom the job shall be done and it co-ordinates production. It is the key point of a production communication system. It creates a direct link between production and sales.

A dispatcher is familiar with the productive capacity of each equipment. He always keeps an eye over the progress of orders which move at different speeds on different routes.

Dispatch Procedure. The product is broken into different components and components into operations.

A route sheet for the part (component) C having three operations on it is shown in Fig. 7.26.