Production Management

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PRODUCTION MANAGEMENT

Edition-2006

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Sr. No. Topics Page No.

1 Introduction 3 to 4

2 Production Planning & Control 5 to 9

3 Factory Location 10 to 21

4 Types of Production 22 to 32

5 Factory Layout 33 to 48

6 Productivity 49 to 52

7 Materials Management 53 to 54

8 Inventory Control 55 to 68

9 Material Handling 69 to 81

10 Job Sequencing 82 to 86

11 Method Study 87 to 91

12 Quality Control & Inspection 92 to 101

13 Safety 102 to 108

QUANTATITIVE MODELS IN PRODUCTION MANAGEMENT

INDEX

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INTRODUCTION


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INTRODUCTION

The management of transformation process of input into output is production management.

Functions of Production Management

• Design and development of production process.

• Production planning and control.

• Implementation of the plan and related activities to produce the desired output.

• Administration and co-ordination of activities of various components and department’s responsibilities for producing the necessary goods and services.

• Control labour cost and maintain quality.

• Manufacture equipment on time on a consistent basis.

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PRODUCTION PLANNING & CONTROL


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Production planning implies formulation, co-ordination and determination of activities for a manufacturing system necessary for the accomplishment of desired objectives, whereas production control is the process of maintaining a balance between various activities evolved during production planning providing most effective and efficient utilization of resources.

Objectives of production planning and control

• Determining the nature and magnitude of various input factors to manufacture the desired output.

• To co-ordinate labour, machines and equipment in the most effective and economic manner.

• Establishing targets and checking these against performance.

• Ensuring smooth flow of material by eliminating bottlenecks, if any, in production.

• Utilisation of under-employed resources.

• To manufacture the desired output of right quality and quantity at right time.

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• The interdependence of various activities/operations involved in the transformation process. Mutual dependence of process makes a system more complex.

• The number of operations, parts and sub-assemblies required to get the final product.

• The nature and magnitude of variation in the capacity of different kinds of machines and equipment.

• The size of orders and the production run, e.g., a large number of orders in smaller lots make the system more complex.

• The nature of the manufacturing system.

Factors determining the nature of production planning and control operations in a manufacturing system

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• Reduces cost of production by minimizing wastage of material and economic utilization of resources.

• Leads to lower investment by means of efficient and balanced utilization of resources.

• Promotes employee morale by avoiding all sorts of bottlenecks.

• Enhances customer satisfaction and confidence.

Importance of production planning and control

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• Liaison with purchase department for efficient and effective procurement of inputs.

• Liaison with marketing department to determine the nature and magnitude of the output.

• To plan the layout of the operations indicating in detail the places/points in the system where various production activities/operations are to be performed.

• Establishment of time schedules for various stages/levels of production by setting up necessary standards.

• Ensuring continuous inspection over the quality of goods manufactured.

• Instituting necessary controls to complete the work according to schedule.

Scope of production planning and control

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FACTORY LOCATION


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FACTORY LOCATION

Introduction

The prime criterion for a preferred location is the least total cost, the minimum delivered-to-customer cost of the product or service. The location of factory may well have a substantial effect upon the operation of the unit and on the factories within a geographical region. No set of rules can be laid down whereby the solution to the problem of location can be solved or programmed. There are, however, a number of factors, such as raw material availability, labour costs, and so on, which should be considered and these factors will be discussed in detail later.

A plant location problem is not encountered everyday, but the factors that can create a problem are constantly developing. Technological improvements make existing products non-competitive. New products replace established lines. A requirement for different materials or a change in the source of materials alters supply costs, power, water or other resource needs are subject to production levels which in turn are a function of demand. Any or all of these factors can force a firm to question whether its plant should be altered at the present location or moved to another locality.

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FACTORY LOCATION

It is worth differentiating between the problem of location and of site. The location is the general area and the site is the place chosen within the location. The decision on siting thus probably proceeds in two stages: in the first stage the general area is chosen and then a detailed survey of that area is carried out to find possible sites.

Thus, a study to identify the best location typically starts with an evaluation of regional factors and progresses to particular communities within the favoured region. Information of a general nature suffices to rate regions. They are compared with respect to market proximity, raw material, tax rates, and other characteristics of special interest to the organisation seeking the site. The factors affecting the choice of a community and a particular site within the community involve specific details.

The models given here for factory location can be used for both the selection of a location and also for the selection of a site in a particular location. The selection of a site decision is probably made by taking into account the more detailed factors than considered for selection of a location (……. is the view pleasant? ……. is there a good restaurant nearby?…….).

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FACTORY LOCATION

Factors affecting location

The following are some of the factors which will influence the choice of location – either for a new construction site or for an available building shed.

1. Integration with other group companies

If the new factory is one of a number of factories owned or operated by a single group of companies, the new factory should be situated such that its work can be integrated with the work of associated factories or warehouses. This will require that the group should be considered as an entity, not as a number of independent units. (There is a high possibility of using the linear programming model for such factory locations.)

2. Availability of transport

In some cases, where products or purchased parts are heavy and bulky, it is important that goods transport facilities shall be readily available. Goods intended largely for export indicate a location near a seaport or a large airfield.

Years ago industrial growth began in seaports because of reliance on inexpensive ocean traffic. As the railroad network grew, the relationship of raw materials to manufacturing to markets became more flexible. Air and trucking transportation encouraged further versatility and industrial centers spread throughout the land. The distance in time between supply and demand is ever diminishing.

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FACTORY LOCATION

3. Availability of materials

While it is true that good transport facilities will enable goods to be obtained and delivered readily, a location near main suppliers will help to reduce cost and permit staff to go readily to see suppliers to discuss technical or delivery problems. Any buyer who has tried to improve deliveries from an inaccessible supplier will bear witness to the considerable difficulties involved.

4. Availability of services

There are six main services that need to be considered, namely –

a) Gas d) Drainage

b) Electricity e) Disposal of waste

c) Water f) Telephone

Certain industries use considerable quantities of water for food preparation, laundries, metal plating, etc. Others use a great deal of electricity for chemical processing and so on. An assessment must be made of the requirements of the factory for as far ahead as possible. Underestimating the needs of any of the services can prove to be extremely costly and inconvenient.

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FACTORY LOCATION

5. Suitability of land and climate

Here, not merely must the genealogy of the area be considered, that is, whether the subsoil can support the loads likely to be placed on it, but also whether the climatic conditions (humidity, temperature and atmosphere) will adversely affect the manufacture. Modern building techniques are such that almost all disadvantages of terrain and climate can be overcome, but the cost of so doing may be high and a different locality could avoid an inflated first cost. For example, cultivating mushrooms in Mumbai rather than in Kashmir.

6. Site cost

As a first cost, the site cost is important, although it is important not to let immediate gain jeopardize long term plans.

7. Availability of amenities

A location which provides good amenities outside the factory – shore, theatres, cinemas, restaurants – is often much more attractive to staff than one which is more remote. This is particularly so where a large proportion of married women are employed who find it convenient to shop for the family during the lunch-break and on the way home. One important amenity in this connection is good personnel transport buses and trains; and some companies find this so vital that they provide special company buses. Other amenities such as good canteen, co-operative stores, child-care are also important.

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FACTORY LOCATION

8. Availability of labour

Labour may be more readily available in some cases than in others. The Department of Trade & Industry can provide information on this point. Certain areas, however, have traditional skills. For example, woollen products in Punjab and coir products in Kerala. It is very rate today that a location can be found which has appropriate skilled labour both readily available. (Big cities, however, could be excluded from this generalization.) The choice has to be made between a location where skilled men exist but are not readily available and where there is a supply of unskilled labour. It must be remembered that new skills can be taught, processes simplified and made less exacting and key personnel moved.

The importance of labour depends, of course, on the particular firm, its policies and its products. If the firm is science-oriented, it should anticipate going to an area where engineers and scientists congregate because it is unlikely that many can be lured to remote sections.

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FACTORY LOCATION

9. Labour stability

Thorough precautions to assure low production costs are of no avail unless the proposed new polant can operate with continuity and tranquil labour-management relations. More than one company has been forced out of business because of unreasonable or prohibitive labour demands. Wage increases and jurisdictional disputes continue to be important points of conflict.

The question of labour stability must be approached from a positive standpoint. There are certain strong points of community attitude that should influence its selection. Perhaps, the most crucial question that can be asked about a community is “What is its past history?”

10. Availability of housing

Where staff has to be recruited other than locally, housing will need to be available. It is general experience that the offer of good housing can be of greater assistance in attracting staff than almost any other factor.

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FACTORY LOCATION

11. Local building and planning regulations

It is important to check at an early stage that the proposed location does not infringe any local regulations. A discussion with the surveyor’s department of the local authority is most desirable. Compliance with pollution standards is a recent location constraint for heavy users of air and motor resources. Reliable fuel and raw material supplies may become critical factors in the future.

12. Room for expansion

It is most unwise to build a factory to the limit of any site. Adequate room for genuine expansion should be allowed. It is dangerous to assume that at a later date the car park can be built on or that the canteen can be used as a productive area.

13. Safety requirements

Some factories may present, or may be believed to present, potential dangers to the surrounding neighbourhood; for example, nuclear power stations and explosive factories are often considered dangerous. Location of such plants in remote areas may be desirable or locating at a safe distance from such factories would be advisable.

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FACTORY LOCATION

14. Adequacy of circulation

The movement of goods, visitors and staff to and from a factory presents a problem not only of easy access but also easy control. There is also a need for emergency access – fire fighting equipment or ambulances – which if impeded could endanger life and seriously affect the company.

15. Political situation

The political situation in potential locations should be considered.

16. Special grants

Government and local authorities often offer special grants, low interest loans, low rentals and other inducements in the hope of attracting industry to particular locations. As these are often areas with large reservoirs of labour, these offers can be most attractive. Every State in India has got different bodies that advise on product selection and plant location. In Maharashtra, these are: SICOM, MIDC, MSSIDC and SISI.

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FACTORY LOCATION

17. Taxation

Few industries have relocated their plants solely because of unfavourable State taxes. It is rather the cumulative effect of this factor and other high cost factors that may prompt a manufacturer to consider relocation.

18. Availability of car space

There is no doubt that the use of cars as a means of transport to and from work will increase, whatever public transport facilities are provided. If open space is not available for car parking, special car-park structures may be necessary.

It is difficult to satisfy all the above factors for plant location. However, a compromise between what is wanted and what can obtained may be the only solution.

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FACTORY LOCATION

1. Integration with other group companies

2. Availability of transport

3. Availability of materials.

4. Availability of services.

5. Suitability of land and climate.

6. Site cost.

7. Availability of amenities.

8. Availability of labour.

9. Labour stability.

10. Availability of housing.

11. Local building and planning regulations.

12. Room for expansion.

13. Safety requirements.

14. Adequacy of circulation.

15. Political situation.

16. Special grants.

17. Taxation.

18. Availability of car space.

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TYPES OF PRODUCTION


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TYPES OF PRODUCTION

It is usually accepted that there are three main types of production, namely: job, batch and flow production. It is important to realize at the outset that these types of production are not necessarily associated with any particular volume of production and that depending upon the circumstances the same task can be undertaken by any of the above methods.

These three different types of production all exhibit distinct characteristics and require different conditions for their effective inception and working. The circumstances in any factory at any time must be carefully considered before a decision is taken as to the method of production to be used. Frequently, the type of production employed depends on the development of the company concerned. Many factories start on a job production basis, proceed as volume increases to batch production methods, in part at least, and finally manage to flow-produce all or some of the products concerned.

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TYPES OF PRODUCTION

JOB PRODUCTION: Job or “make complete” production is the manufacture of a single complete unit by an operator or group of operators, and a number of identical units can proceed in parallel under job production conditions. Bridge-building, dam-construction and ship-building are common examples of the job production industries. Job production is characterized by the fact that the whole project is considered as one operation and work is completed on each product before passing on to the next. Labour tends to be versatile and highly skilled, capital investment is high, while control is relatively simple, being largely exerted by the operator or group. In the case of production of a single specialized equipment, it is inevitable that job production should be used, but in the case of quantity manufacture it is conceivable though unlikely that job production could also be used.

BATCH PRODUCTION: As quantity increases, work may be carried on under batch production methods. Such methods require that the work on any product is divided into parts or operations, and that each operation is completed throughout the whole batch before the next operation is undertaken.

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TYPES OF PRODUCTION

By its use some degree of specialization of labour is possible, and capital investment is kept low, although the organisation and planning required to ensure freedom from idle and waste time is considerable. It is in batch production that the production control department can produce most benefits, and these can often be spectacular, but it is also in batch production that it will be found most difficult to organize the effective working of a production control department.

In order to clarify the difference between job and batch production, consider a small quantity of units, say five, being made by a number of operators. Under job production conditions the operators would be divided into five groups and each group would be responsible for the complete manufacture of one unit. Under batch conditions, however, the work content of each unit would be broken into a number of operations not necessarily of equal work content, and the operators would again divide into groups. The first group would then complete the first operation on all five units, passing the batch as a whole on to the next group and so on until the manufacture was complete. In general, the batch is not passed on from one operator or group to the next until all the work is completed on that operation. Transferring part batches can often lead to considerable organizational difficulties. It should be noted that during the batch manufacture of the five units mentioned above, four units are always at rest, no work being carried out on them. In fact, the rest periods of any

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TYPES OF PRODUCTION

one unit from a batch of a total = (n-1)/n x 100 percent, of the total batch production time. This is characteristic of batch production, where the work content of the material increases irregularly and results in a substantial work-in-progress. In addition to the rest period indicated above, the organizational difficulties of batch production may well generate other rest times, where numbers of batches are passing through the same production stages, and competing for resources, it is usual to move a batch from an operator or machine into a “buffer” or “work-in-progress” stores, to wait there for the next operator or machine to become available. The sequencing of batches from different jobs to reduce this source of “rest” is one of the most difficult problems encountered in the management of a production unit, and however successfully it is solved, there will inevitably be some element of rest time brought about by this competition for resources. Thus in batch production, there is a rest period for each unit in the batch, whist work is proceeding on other members of the batch, and another rest period whilst the whole batch is in buffer store. This often results in the time between the origination of work on a batch and its eventual completion being much greater than the simple manufacturing time for the batch.

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TYPES OF PRODUCTION

The effect of the considerable time lag between an initial investment in material and its subsequent translation into cash upon the sale of the finished product can be very serious in terms of the investment in capital which is tied up in the work in progress. On the other hand, the presence of buffer stores permits the production unit to absorb shocks and changes, thus building in some element of flexibility, and it assists in making more effective use of the various limited manufacturing resources. This balancing of investment in material against investment in resources is a continually recurring task, and one to which there is rarely a simple unique answer.

FLOW PRODUCTION: Batch production is characterized by the irregularity in the increase of work added to the basic material. Batch production turns into flow production when the rest period mentioned above vanishes. In other words, flow production can be defined as production during which work content of the product continually increases. Flow production then means that as the work on each operation is complete, the unit is passed to the next work stage without waiting for the work to be completed on the total batch. In order that this can flow smoothly, the times of each operation must be of equal length, and there must be no movement off the production line. For example, inspection must be physically located within the flow production line and the inspection function must not occupy more than the unit operation time. Furthermore, since the whole system is balanced, any fault affects not

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TYPES OF PRODUCTION

only the stage at which the fault occurs, but also all the stages in the production line. Thus, a fault occurring at one stage of a flow production line which cannot be cleared within the time cycle of the line, will result in that stage being held up. This, in turn, causes all stages previous to it to be held up and all stages subsequently to run out of work. The line as a whole, therefore, must be considered as a single entity and not allowed to break down at any point at all.

In order that flow production can function satisfactorily, the following requirements must be met:

1. There must be continuity of demand. Should demand be spasmodic, there will be a build-up of finished work which can give rise to storage difficulties. Alternatively, if production is caused to fluctuate along with demand, then the setting up and balancing of the flow line will need to be carried out frequently, giving an excessively high total cost. In industries with widely varying demands, a leveling out is achieved by making for stock during the “flat” periods, the stock supplementing the current production during “peak” periods.

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TYPES OF PRODUCTION

2. The product must be standardized. A low line is inherently inflexible and cannot accommodate variations in the product. A quasi variety is achieved by varying finished, decorations and other externals.

3. Material must be to specification and delivered on time. Due to the inflexibility mentioned above, the flow line cannot accept the variations in material which can be incorporated in a batch or job production process. Furthermore, if material is not available when it is required the effect is very serious, since the whole line will be frozen.

4. All stages must be balanced. If the requirement that the material does not “rest” is to be fulfilled, then the time taken at each stage must be the same. This can lead to inefficiency due to inability to balance stages. For example, assume a product with a work content of 10 hours has to be made at a rate of 400 a week, and the normal working week is 40 hours, then –

The total weekly work content = 400 x 10 hours.

Hence the number of operations required = (400 x 10)/40 = 100

And the time for each operation = (100 / 600) hours

= 6 minutes.

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TYPES OF PRODUCTION

To meet the required production, then, a flow line with 100 stages needs to be set up, the work content of each stage being 6 minutes. It may be found, however, that one stage has a work content of only 3 minutes and that it cannot be compounded with any other stage. Under these circumstances, this stage must have an idle time content of 3 minutes. This is known as “synchronizing loss” and the only way of avoiding this would be to increase the rate of production so that, in fact, all stage times could be reduced to 3 minutes. In the situation where an element cannot be reduced to the required stage time – for example, a machine-controlled operation is 10 minutes – then resources must be increased so that the effective operation time becomes less than the stage time. This can lead to an under-utilisation of resources.

5. All operations must be defined. In order that the line will maintain its balance, all operations must remain constant. This can only be done if the operations are recorded in detail.

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TYPES OF PRODUCTION

6. Work must conform to quality standards. In job or batch production, variation in quality at one stage can be compensated for by extra work elsewhere. In flow production this cannot happen, since each stage has a defined operation.

7. The correct Plant and Equipment must be provided. Lack of correct apparatus will unbalance a line, causing weaknesses throughout the whole sequence.

8. Maintenance must be by anticipation not default. If equipment breaks down at any one stage, the whole line is halted. To avoid this, a programme of preventive maintenance must be in force.

9. Inspection must be “in line” with production. Unless the inspection stage is balanced with the rest of the production, a dislocation to the flow will inevitably take place.

The achievement of the above requires considerable pre-production planning, particularly in assuring that the correct material is delivered on time, and that the operations are of equal length of time. Common examples of flow production are the manufacture of motor-cars, watches, domestic radio receivers, etc.

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TYPES OF PRODUCTION

(a) The direct labour content will be reduced, since the comprehensive pre-production planning which is necessary will often produce economies in time.

(b) Assuming the product is initially designed correctly, then reproducibility, and hence the accuracy, is high.

(c) Since inspection is “in line”, deviations from standard are rapidly picked up.

(d) Since there is no rest period between operations, work in process is at a minimum.

(e) Again, since there is no waiting period, the provision of work-in-process stores is unnecessary, and the total storage space required is minimized.

It must be noted that flow-production is not necessarily large-scale production.

The following advantages can be derived from the effective institution of flow production techniques –

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FACTORY LAYOUT


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FACTORY LAYOUT

Introduction

The disposition of the various parts of a plant, along with all the equipment used therein, is known as the Plant Layout, which should be designed to enable the plant to function most effectively. Plant Layout is a companion problem to Plant Location. A decision to relocate provides an opportunity to improve total facilities and services. A decision not to relocate is often accompanied by plans to revise the current plant arrangement. The re-layout must be designed to reduce increasing production costs that gradually evolve from piecemeal expansion or to introduce an entirely new process. In either case, the re-layout strives to maximize production flow and labour effectiveness.

In this section, we shall explore the relationship of production departments – grouping of production activities – rather than individual machines or architectural features. A facility layout of a hospital would concern emergency rooms, operating theatres, patient rooms and even the parking lot, but it would not initially involve the location of an x-ray machine or a cash register. However, the detailed equipment or facilities layout would follow the same methodology as the overall departmental layout.

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FACTORY LAYOUT

Objectives of Plant Layout

The chief objectives are likely to be improved operations, increased output, reduced costs, better services to customers, and convenience and satisfaction for company personnel.

Types of Plant Layout

There is a layout by fixed position or by fixed material location. This is a layout where the material or major component remains in a fixed place. All tools, machinery, men and other pieces of material are brought to the major component. The complete job is done or the product is made with the major component staying in one location. Ship-building and heavy construction of dams, bridges and buildings are typical examples. Advantages are:

1. Handling of major assembly unit is reduced.

2. Highly skilled operators are allowed to complete their work at one point and responsibility for quality is fixed on one person or assembly crew.

3. Frequent changes in products or product design and in sequence of operations are possible.

4. The arrangement is adapted to a variety of products and intermittent demands. It is more flexible in that it does not require highly organized or expensive layout engineering, production planning or provisions against breaks in work continuity.

The disadvantage is that the required movement of materials and machines may be cumbersome and costly.

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FACTORY LAYOUT

Product, Flow, Sequential or Line Layout

Here the Plant is laid out according to the requirements of the product. This is typical of flow production. One product or one type of product is produced in one area. But unlike layout by fixed position the material moves. This layout places one operation immediately adjacent to the next. It means that any equipment used to make the product, regardless of the process it performs, is arranged according to the sequence operations.

Diametrically, this is illustrated in Figure 1, where Product 1 goes first to machine-A, then to machine-B, then to machine-C, these machines being used exclusively.

for Product 1, Product 2 and Product 3 have their own line of machines (K,L,M, and R,S,T) and, even though machines A,K,R are identical and interchangeable, work is not transferred from one product line to another.

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FACTORY LAYOUT

Advantages are:

1. Reduced handling of material.

2. Reduced amounts of material-in-process, allowing reduced production time and lower investment in materials.

3. More effective use of labour (a) through greater job specialization and (b) through ease of training.

4. Easier control of production allowing less paperwork and effective supervision.

5. Reduced congestion of floor space otherwise allotted to aisles and storage.

Disadvantages are:

1. Unless volume is very high, machine utilization may be low, with a subsequent high capital investment.

2. One machine breakdown may immobilize a complete production line.

3. The system is inflexible, being unable to accommodate changes.

4. Unless the production is true flow production and all operations balanced, buffer stock (work-in-process) will be inevitable.

5. The pace of the line is set by the slowest operation.

6. Any changes in product design, volume, etc., in the line will normally require a major investment.

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FACTORY LAYOUT

Process of Functional Layout

In this type of layout, plant is grouped according to its function. Thus, all drilling machines will be together, as will all milling machines, presses, lathes and so on. This is most commonly met with in jobbing product. This is illustrated in figure, where products 1, 2 and 3 all go to machine-A, then after processing, product 1 goes to machine-B and thence to machine-C, while products 2 and 3 go to machine-L. Product 2 then goes to machine-C, while product 3 goes to machine-T. To allow all machines to be fully loaded, work-in-progress stores are necessary between each machine.

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FACTORY LAYOUT

Advantages are:

1. Better machine utilization allows lower machine investment.

2. It is adapted to a variety of products and to frequent changes in sequence of operations.

3. It is adapted to intermittent demand (varying production schedules).

4. The incentive for individual workers to raise the level of their performance is greater.

5. It is easier to maintain continuity of production in the event of –

(a) machine or equipment breakdown;

(b) shortages of material;

(c) absent workers.

Disadvantages are:

1. Substantial pre-production planning is required if machine loading is to be high.

2. Control is difficult.

3. Buffer stocks are essential; hence, relatively high investment in raw materials and work-in-progress.

4. It increases handling, space requirements and production time.

5. Close supervision is essential.

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FACTORY LAYOUT

Which type of layout to use?

Use layout by fixed position or fixed material location when –

1. Material forming or treating operations require only hand tools or simple machines.

2. Making only one or a few pieces of an item.

3. The cost of moving the major piece of material is high.

4. The skill of workmanship lies in the abilities of the workers or it is desired to fix responsibility for product quality on one worker or crew.

Use layout by product when –

1. There is a large quantity of pieces or products to make.

2. The design of the product is more or less standardized.

3. The demand for it is fairly steady.

4. Balanced operations and continuity of material flow can be maintained without difficulty.

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FACTORY LAYOUT

Use layout by process when –

1. Machinery is highly expensive and not easily moved.

2. Making a variety of products.

3. There are wise variations in times required for different operations.

4. There is a small or intermittent demand for the product.

In actual practice, most layouts are a combination of the basic layouts discussed above. They are made to utilize the advantage of all three types of layout.

Criteria for a good layout -

While the techniques employed in making a layout are normal work-study techniques, the process is a creative one which cannot be set down with any finality, and one in which experience plays a very great part. Furthermore, it is not possible to define a good layout with any precision. However, there are certain criteria which will be satisfied by a good layout, and these are discussed below:

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FACTORY LAYOUT

1. Maximum Flexibility

A good layout will be one which can be rapidly modified to meet changing circumstances. In this context, particular attention should be paid to supply points, which should be ample and of easy access. These can be simply and cheaply provided at the outset of a layout, and failure to do so can often present very necessary modifications to unsatisfactory, outdated or inadequate layouts.

2. Maximum Coordination

Entry into, and disposal from, any department should be in such a manner that it is most convenient to the issuing or receiving departments. Layout requires to be considered as a whole and not parochially.

3. Maximum use of Volume

A factory must be considered as a cubic device, as there is airspace above the floor area. Maximum use should be made of the volume available. Conveyors can be run above lead height and used as moving work-in-progress stores, or tools and equipment can be suspended from the ceiling. This principle is particularly true in stores, where goods can be stacked at considerable heights without inconvenience, especially if modern lift trucks are used.

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FACTORY LAYOUT

4. Maximum Visibility

All men and materials should be readily observable at all times; there should be no “hiding places” into which goods can get mislaid. This criterion is sometimes difficult to fulfill, particularly when an existing plant is taken over. Every piece of partitioning or screening should be scrutinized most carefully while introducing undesirable segregation and reducing effective floor space.

5. Maximum Accessibility

All servicing and maintenance points should be readily accessible. For example, a machine should not be placed against a wall in such a manner that a grease-gun cannot reach the grease nipples. The maintenance under these circumstances is likely to be skimped at best and will occupy excessive time. Similarly, a piece of plant in front of a fuse box will impede the work of the electricians and may cause unnecessary stoppage of the machine when the fuse box is opened. If it is impossible to avoid obscuring a serviced point, then the equipment concerned should be capable of being moved. It should not be a permanent installation.

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FACTORY LAYOUT

6. Minimum Distance

All movements should be both necessary and direct. Handling material adds to the cost of the product but does not increase its value. Consequently, any unnecessary or circuitous movements should be avoided. It is a common failing for material to be moved off a work-bench to a temporary storage point. This intermediate rest place is often unnecessary and unplanned, being used only because an empty space appears convenient. The providing of ‘extra’ shelves, benches and tables should be questioned very thoroughly and avoided if possible.

7. Minimum Handling

The best handling is no handling, but where handling is unavoidable it should be reduced to a minimum by the use of conveyors, lifts, chutes, hoists and trucks. Material being worked on should be kept at working height and never placed on the floor if it is to be lifted later.

8. Minimum Discomfort

Poor lighting, excessive sunlight, heat, noise, vibrations and odour should be minimized and if possible counteracted. Apparently, trivial discomforts often generate troubles greatly out of proportion to the discomfort itself. Attention paid to the lighting and general decoration and furniture can be rewarding without being costly. Recommendations on the intensity of lighting for various tasks are published and most manufacturers of lighting equipment will provide useful advise on the subject.

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FACTORY LAYOUT

9.Inherent Safety

All layouts should be inherently safe, and no person should be exposed to danger. Care must be taken not only of the persons operating the equipment but also of the passers-by, who may be required to go behind a machine, the back of which is unguarded. Adequate medical facilities and services must be provided, and these must satisfy the Chief Inspector of Factories. Experience shows that the factory inspector is not only most competent to advise on these matters, he is always ready to be of assistance.

10.Maximum Security

Safeguards against fire, moisture, theft and general deterioration should be provided, as far as possible, in the original layout.

11.Unidirectional Flow

Work lanes and transport lanes must not cross. At every point in a factory, material must flow in one direction only, and a layout which does not conform to this will result in considerable difficulties, if not downright chaos, and should be avoided.

46

FACTORY LAYOUT

12.Visible Routes:

Definite lines of travel should be provided and, if possible, clearly marked. No gangways should ever be used for storage purposes, even temporarily.

The co-existence of a large number of criteria makes the definition of an “optimum” schedule virtually impossible. Furthermore, the writing of a computer programme for plant layout becomes a task of considerable difficulty unless some very drastic simplifications are made.

` 1. Maximum Flexibility 2. Maximum Coordination

3. Maximum Use of Volume 4. Maximum Visibility

5. Maximum Accessibility 6. Minimum Distance

7. Minimum Handling 8. Minimum Discomfort

9. Inherent Safety 10. Maximum Security

11. Unidirectional Flow 12. Visible Routes

Principles satisfied by a good Layout.

47

FACTORY LAYOUT

Advantages of a good Layout

A layout satisfying the above conditions will have the following advantages over one which does not:

1. The overall process time and cost will be minimized by reducing unnecessary handling and by generally increasing the effectiveness of all work.

2. Labour supervision and production control will be simplified by the elimination of hidden corners in which both men and materials can be misplaced.

3. Changes in programme will be most readily accommodated.

4. Total output from a given plant will be as high as possible by making the maximum effective use of available space.

5. A feeling of unity amongst employees will be encouraged by avoiding unnecessary segregation.

6. Quality of products will be sustained by safer and better methods of production.

48

FACTORY LAYOUT

Symptoms of a poor Layout

The main symptoms of a poor layout are:

1. Lack of control.

2. Congestion of men and materials.

3. Excessive re-handling.

4. Long transportation lines.

5. Frequent accidents.

6. Low worker performance.

49

PRODUCTIVITY


50

PRODUCTIVITY

Productivity is a measure of how much input is required to produce a given output, i.e., it is the ratio of output to input.

Factors affecting productivity Technology employed. Tools and raw materials used. Organisation structure. Planning and scheduling of work. Plant layout. Innovations. Personnel policies. Work environment. Materials management. Skills of the workforce. Health, attitude towards management. Training to the workers. Discipline. Transport facilities.

51

PRODUCTIVITY

Techniques to improve productivity

Better planning and training of employees. Use of time and motion studies to study and

improve work performance. Better transportation and material handling

system. Providing work incentives and other benefits to

workers. Involvement of workers in decision-making. Improvement in technology of production process. Simplification, standardization and specialization

techniques like PERT, CPM. Better and efficient utilization of resources. Use of linear programming and other quantitative

techniques. ABC analysis to identify more important items and

then apply inventory control to reduce capital investments.

52

PRODUCTIVITY

Measurement of productivity

1) Labour productivity = amount of output

amount of labour

2) Capital productivity = sales turnover

capital employed

3) Profit productivity = profit

investment

53

MATERIALS MANAGEMENT


54

MATERIALS MANAGEMENT

Materials Management is the planning, directing, controlling and coordinating those activities which are concerned with materials and inventory requirements, from the point of their inception to their introduction into the manufacturing process. It begins with the determination of materials, quality and quantity and ends with its issuance to production to meet customer’s demand as per schedule and at the lowest cost.

Objectives of Materials Management Regular uninterrupted supply of raw materials to ensure continuity of production. Provide economy in purchasing and minimizing waste. Minimise storage and stock control cost. Minimise cost of production. Purchase items of best quality at the most competitive price.

Stages of Materials Management

Decision stage. Sourcing stage. Production planning stage. Ordering stage. Receiving stage. Inventory control.

55

INVENTORY CONTROL


56

Inventory control

Inventory is referred to accumulation of items or goods required by the company for its products or as an aid to production. A manufacturing firm generally carries the following 7 major classification of items with inventories:

• Major raw materials.

• Finished components as work-in-progress.

• Finished goods.

• Tools and fixtures.

• Supplies, e.g., welding rods, oil and grease, electrical supplies, office supplies, consumables, etc.

• Machinery spares such as bearings, bolts, oil seals, springs, etc.

INVENTORY CONTROL

57

Purpose of carrying inventory

• To gain economy in buying.

• To keep pace with changing market conditions.

• To satisfy demand during the period of replenishment.

• To carry reserve stocks to avoid stock-outs.

• To stabilize production.

• To prevent loss of sales.

• To satisfy other business constraints.

Objectives of Scientific Inventory Control

• Service to customers.

• Effective use of capital.

• Economy in buying.

• Reduction of administrative workload.

• Minimisation of risk obsolescence and deterioration.

• Stability of production activity.

• Space to install scientific inventory control system.

INVENTORY CONTROL

58

STEPS TO INSTALL ASCIENTIFIC INVENTORY CONTROL SYSTEM

INVENTORY CONTROL

59

EOQ MODEL

Assumptions:

• The demand of the item occurs uniformly over the period at the known rate.

• The replenishment of stock is instantaneous.

• The price per unit is fixed and is independent of the order size.

• The cost to place an order and process the delivery is fixed and does not vary with the lot size.

• The inventory carrying charges vary directly and linearly with the size of the inventory and are expressed as a percentage of average inventory investment.

• The item can be procured in the quantities desired, there being no restriction of any kind.

• The item has fairly long shelf life, there being no fear of deterioration or spoilage.

INVENTORY CONTROL

60

Mathematical Treatment of the model:

The symbols used

Annual consumption of the item (units) : S

Unit price (Rs.) : Cu

Order quantity (units) : q

Procurement cost per order (Rs.) : Cp

Inventory carrying cost expressed as a : I

Percentage of average investment .

Preparation of model

Two costs are involved for the inventory decisions :

Procurement cost and Inventory carrying cost.

INVENTORY CONTROL

61

Annual Procurement Cost

No. of orders per year

Procurement cost per order= x

Annual Consumption

Order quantityProcurement cost per order

= x

S

qCp= x

INVENTORY CONTROL

62

Annual Inventory Carrying Cost

Average inventory investment

Inventory carrying cost= x


Order Quantity

Price per Unit

= x1

2x

Inventory carrying cost

q

2Cu= x x i


+ q

2Cux x i S

qCp= x

INVENTORY CONTROL

63

To determine economic order quantity (qo) – the quantity that minimises the total cost – we must differentiate ATC with respect to decision variables q and set the first derivative to zero.

Therefore - S . Cp

q2

Cu x i

2= + 0=d(TAC)

dq

2 . S . Cp

Cu . i=q2

o (When order quantity equal EOQ)

then q = qo

=qo 2 . S . Cp

Cu . i√

INVENTORY CONTROL

64

Therefore -

Economic order Quantity =

2 x [ Annual Consumption (units)] x [ Procurement cost/order ]

Price /unit x Inventory carrying cost√

INVENTORY CONTROL

65

INVENTORY CONTROL - ILLUSTRATIONS

• A company uses 75 numbers of an item per month. Each unit cost the company Rs.25/-.The cost of ordering is Rs.36 and inventory carrying charges is 1.5% of average inventory investment per month respectively.

In what economic lots should the item be purchased to minimize total cost? It minimizes waste by identifying the causes of excessive variability in the quality of product.

• Impellers are procured by the water pump manufacturer from a local firm and are consumed at an average rate of 500 numbers per month. If the procurement cost is Rs.36 per order and the cost of holding it in stock is Rs.1.20 per unit per year, determine the quantity that should be procured at a time to optimize the cost involved.

If the consumption of the above item increases to 40 numbers per day and its actual inventory carrying cost is Rs.0.2 per unit per day, what shall be its revised EOQ quantity?

• A manufacturer of control panels spends Rs.3400 per annum on its purchasing activities. Rs.67200 is spent each year in maintaining inventory of Rs.4.21 lacs (expenses referred above are only the variable portion of the total expense).Around 850 orders are placed every year to replenish stocks of the various items. One of the items whose annual consumption is 9600 numbers is bought by the company at the rate of Rs.30 each. How frequently should the company receive the staggered deliveries and in what quantities?

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• The requirements of a particular size of oil seal at an automobile firm is estimated at 40,000 numbers next year. The oil seal is available locally with a lead time of two weeks and it cost Rs.10 each.

The cost of order writing, follow up, primary inspection and inward stores is computed at Rs.50 per order. The holding cost is estimated at Rs.2 per unit for storage plus 20% per unit per year on account of opportunity cost of the capital.

a) How many units should the firm order at a time to optimize the inventory cost?

b) What is the annual inventory cost?

• ABC Pump Company uses 60,000 valves per year and the usage is fairly constant at 5000 valves per month. Each valve cost the company Rs.1.50. The carrying cost for the company has been estimated at 15% of the average inventory investment. The cost to place an order and process the delivery is Rs.30.

a) Calculate economic order quantity.

b) What is stock turnover rate ignoring safety stocks if EOQ is ordered frequently?

c) What will be the effect on total cost if stock turnover rate is reduced to one third by

infrequent ordering?

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• A manufacturer of a hand grinder requires a special roller bearing at the rate of 300 numbers per year. Each bearing cost the company Rs.36. The procurement cost and the inventory carrying cost have been calculated at Rs.30 and 20% respectively.

If the supplier offers discount of Rs.2 per bearing on an order of 200 or above, should higher quantity be purchased?

• A chemical firm buys 2500 units of a particular item annually from a vendor at a cost of Rs.3 per unit. It has now received a revised price schedule from the vendor which is as follows:

Order quantity Price per unit

Less than 500 units Rs. 3

Between 500 and 1250 units Rs.2.90

1250 units and above Rs.2.85

The total of placing an order and executing the delivery once is Rs.25 and inventory carrying cost as a percentage of average inventory investment is 20%. Determine the economic order quantity of the item.

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• Monthly consumption of an item having unit price of Re.1 has been estimated at 300 units. The inventory carrying cost and the procurement cost for the company have been computed at 18% and Rs.36 per order respectively. Stock records show that this item can normally be procured within a period of one month. If the company adheres to the policy of one month safety stock for all ‘A’ and ‘B’ category of items.

Calculate –

re-order quantity

minimum level

re-order level

maximum level

average inventory

assuming re-order level system of replenishment.

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MATERIAL HANDLING


70

MATERIAL HANDLING

Material handling may be broadly defined as the movements of materials from one place to another. It may be picking up or putting down, moving horizontally or vertically or in any inclined plans of materials, of any kind in their raw, semi-finished or finished state.

OBJECTIVE

Material handling often does not add anything to the value of the product but only increases the cost. Handling costs constitute a substantial portion of the total cost of production. Besides, material handling is also found to be responsible for a large percentage of product damage. 80 to 90% of industrial accidents and other disadvantages. In spite of this, material handling is an essential feature of industrial activity. Materials have to be moved from one place to another without which all the activities would come to a standstill. Material handling often accounts for improved utilization of men and machines, and provides for specialization of skills and the related advantages.

Since material handling cannot be eliminated completely in any organisation, the objective of material handling may be stated as instituting an efficient system of handling. Eliminating unnecessary and wasteful handling system saves money and time, reduces damage to materials and makes the work safer.

71

MATERIAL HANDLING

Some Principles

Some of the major principles in the design of an efficient system of material handling are:

a) Reduce handling to a minimum: As far as possible, materials should always move towards completion, over the shortest distance without back-tracking. A large amount of handling can be eliminated by planning the location of operations so that one operation finishes right where the next begins. The flow of product should receive top priority in planning of layout.

b) Avoid re-handling: It may not be possible to eliminate re-handling completely. Nevertheless, re-handling is a wasteful and costly operation. Re-handling can be reduced by (i) not keeping anything on floor, (ii) avoiding transfers from floor to container or vice versa or from container to container, and (iii) avoiding making of materials.

c) Combine handling with other operations: Many times, handling may be made a productive activity by combining with other operations, such as production, inspection and storage. In process industries, materials undergo physical and chemical changes while in movement, handling devices may be used as live storage of materials may be sorted and inspected while they are being handled.

72

MATERIAL HANDLING

d) Ensure safety in handling: Safety is a key word in handling. A large percentage of industrial accidents are attributed to poor handling practices. Even costlier in terms of money is the damage to equipment and products due to improper handling methods. A good handling system should ensure safety to workers and materials. Manual handling of heavy objects, materials scattered on the floor or projecting into aisles are but a few causes of accidents. Keeping gangways and aisles clear is one of the primary precautions against accidents in handling.

e) Handle materials in unit loads: It is easier and quicker to move a number of materials at a unit rather than piece by piece. Modern material handling devices are designed to take advantage of unutilized loads.

f) Use gravity where possible and mechanical means, if necessary: The simplest and cheapest way to handle materials is by using gravity. Often chutes and inclined boards can be conveniently used to transport materials quickly to the point of use without much investment on costly handling equipment. Where it is not possible to use gravity for various practical reasons, some mechanical means should be considered. Lifting and carrying of heavy materials mechanically saves time and reduces fatigue of workers.

73

MATERIAL HANDLING

g) Select proper handling equipment: There are as many types of handling equipment available today as the number of materials to be handled. And any single equipment may not solve all handling problems. It is therefore necessary to choose the equipment suitable for the job under consideration. The equipment selection needs to be done carefully so that there is an efficient coordination of all handling, resulting in overall economy. Use of standardized equipment facilitates maintenance and repair.

Another important factor in the selection of equipment is flexibility. Industrial activity is subject to constant changes and handling equipment should provide for this change. In other words, the equipment selected should be capable of a variety of uses and applications.

h) Reduce terminal time of equipment: The advantage of mechanical and power equipment would be lost of they are made to wait during loading and unloading which may take considerable amount of time. By reducing this waiting time the handling equipment would be released for more productive work. There are various mechanical devices like trailers, tipping arrangements, cranes and hoist arrangements, to quicker loading and unloading operations.

74

MATERIAL HANDLING

i) Buy equipment for overall savings: In selecting equipment, savings in overall handling cost must be the guiding principle rather than the first cost of equipment. Arriving at the handling cost is a difficult problem but a fairly accurate estimate can be obtained by determining the handling elements and applying work measurement.

In India, labour is still comparatively less costly and a longer period may have to be allowed for amortizing the handling equipment. All direct and indirect savings are to be taken into consideration while deciding on handling equipment.

j) Use labour consistent with handling jobs: Manual handling could be done by unskilled labour, whereas mechanical handling may require semi-skilled or skilled workers. Proper allocation of skills helps in overall economy. As far as possible, direct production operators should not be used for handling operations. It is preferable to have a separate gang of material handlers to ensure proper utilization of production workers.

k) Train workers and maintain equipment: Careful operation and proper upkeep are essential for getting the maximum out of the handling equipment. Careful selection and training of employees in principles, operation and safety rules and planned maintenance of equipment are worthwhile investments in the long run.

75

MATERIAL HANDLING

Material Handling Equipment:

A pre-requisite to the design of a material handling system is a knowledge of the different kinds and types of material handling equipment that are available. Although there are hundreds of different handling equipment, all can be placed in three major categories.

Conveyors: The first major class of material handling equipment consists of conveyors. A conveyor is any device which moves material in either a vertical or horizontal directions between two fixed points, and this movement can take place either continuously or intermittently.

One of the distinct characteristics of conveyors is that they create a relatively fixed route. Consequently, they are employed primarily in continuous manufacturing in which materials leaving one work station invariably go to some other specific work station in the production line. Therefore, it is possible to connect two such work stations by material handling equipment which is capable of moving materials only between two fixed points. In intermittent manufacturing, however, materials leaving one work station may go to any number of other work stations. Obviously, it would not be feasible to set up a network of conveyors which would provide all the possible route which materials may have to follow.

76

MATERIAL HANDLING

A second characteristic of conveyors is that, unless they are of the portable type, they occupy space continuously. As a result, they must be installed in locations in which they will not interfere with the flow of other traffic. For example, if two work stations are located on opposite sides of an aisle which is used as a path of travel by men and trucks, a floor mounted conveyor could not be used to link these two work stations. Therefore, unless cross traffic can be bypassed, no serious consideration would be given to the use of conveyors.

In so far as listing of different types of conveyors is concerned, the ones most frequently encountered are the following:

Gravity Conveyor: As the name implies, gravity conveyors rely on nature for their driving force. Roller, wheel and chute conveyors call in this category. They are used primarily to move materials and are a relatively inexpensive type of conveyor as a rule, although for some applications, such as in moving grain, they can be quite expensive. Compared with other types, gravity conveyors are highly flexible and transportable and are well suited to variable paths. Movement is restricted, however, to route that involves some degree of vertical fall.

77

MATERIAL HANDLING

Endless chain conveyors: These conveyors are usually driven by an electric motor and, as a consequence, are usually more expensive than gravity conveyors. They have several important advantages, however. These conveyors can move materials up as well as down, and the progress of the materials can be closely controlled. In addition, special carrying devices and containers can be attached to the chain. Frequently, production tasks such as dip painting, cleaning and washing may be performed as the conveyor moves. Finally, by varying the speed of the conveyor at different points, or by building loops into it, work-in-process inventory may be stored between operating stages.

Belt conveyors: Belt conveyors are also driven by electric motors. These belts are usually made of some flexible material such as rubber. However, special belts are used in many industries. In the baking industry, for example, Teflon-coated metal is utilized to prevent sticking. The belt passes over rollers, which normally create a trough in the centre of the belt where the materials are concentrated. Conveyors of this sort are used mainly for transporting bulky material. Baggage is moved from the ground to the baggage compartments of airplanes and shipped by conveyor belts. They are also used to move ores from the min face to work areas. Stock brokerage firms and insurance companies even use them to route papers to various parts of their buildings. When work is to be performed, however, the materials must be taken from the belt and later replaced when the work is completed.

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MATERIAL HANDLING

Other conveyor equipment: Pipelines are often employed for moving liquids and gases such as gasoline and natural gas. Pneumatic tubes are used in some firms for rapid dissemination of internal communications.

Screw conveyors have been successfully used to lift materials in both grain elevators and food-processing industry to move delicate foods in steady streams without damage.

Industrial trucks: Industrial trucks which represent the second category of material handling equipment, are vehicles powered by hand, fuel or electricity, which are capable of transporting materials horizontally between any two points. As opposed to a conveyor, a truck is able to more from one location to any other location so long as suitable traveling surface is available and its path of travel is not obstructed. For this reason, the prevalent method of handling material in a firm engaged in intermittent manufacturing is by means of trucks. The variable path of travel they are able to follow permits them to transport materials from one work station to any of a number of other work stations at which a subsequent operation is scheduled to be performed.

A second desirable feature of trucks is that they occupy a given amount of space intermittently. This means that a certain amount of space in a given location is required to house a truck for only as long as the truck is in that location. As soon as the vehicle is moved, the space is free for other uses.

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MATERIAL HANDLING

As in the case of conveyors, there are many types of trucks, and each of these can be equipped with a variety of attachments. But the most important ones are as follows:

Hand operated vehicles, tractors, platform trucks, forklift trucks, straddle carriers.

When the loads are not too heavy and the hauls are short, manual equipment may be used. However, when the load size and weight and the distances to be traveled are great, powered equipment is used. Today, most industrial trucks are powered. They are generally equipped with forks or platforms that can be raised or lowered to facilitate the movement and storage of materials, and for this reason the loads are generally placed on pallets or skids.

Cranes and hoists:

The third classification of material handling equipment consists of cranes and hoists. This equipment is able to move materials vertically and laterally in any area of limited length, width and height. It is used primarily when material must be lifted prior to being moved from one point to another. These points may represent different work stations or different locations at a single work station. For example, if a part is large or heavy, the operator may find it necessary to use a hoist to aid him in loading or unloading the machine. Subsequently, a crane may be used to move the part to another work-station.

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MATERIAL HANDLING

One of the advantages of cranes and hoists is that they are able to transport objects through the overhead space in the plant. Consequently, space is utilized, which would otherwise be unused, and floor space is freed for other uses. To illustrate, it might be possible to move a large heavy casting by means of a truck from one work-station to another. However, this would create a need for wide aisles at appropriate locations in the plant. If a floor space is at a premium, a more desirable alternative would be to transport the item through the air by means of a crane which would either eliminate the need for certain aisles or, at least, permit the use of aisles which may be required for the movement of smaller objects. But there are cases in which cranes and hoists are used, not because they free floor space but because they are the best available means of positioning material in a particular location.

However, when considering cranes and hoists, it is important to keep in mind that any one unit of this equipment is capable of serving on a limited area.The size and shape of this area will vary with the kind of crane or hoist being used. Nevertheless, the equipment is somewhat more flexible in this respect than are conveyors, but not a flexible as are industrial trucks. Also, it will be found that cranes and hoists are as likely to be used intermittently as in continuous production.

Again, there are many types of equipment which are placed in the crane and hoist category. However, the most common ones are the following: overhead bridge cranes, gantry cranes, jib cranes, elevators, lifts, chain hoists, air hoists, electric hoists.

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MATERIAL HANDLING

Overhead bridge crane are commonly employed in factories where large, heavy pieces of equipment such as electrical transformers, generators and power regulators are manufactured. These cranes ride on parallel overhead rails and are usually designed so that they can service any place in the work area of the plant.

Another common type of crane, which is designed for outside work, is the gantry crane. It moves in limited areas on wheels, providing its own superstructure, and is chiefly used for such tasks on moving lumber and loading and unloading in railroad freight yards. Large cranes of this sort must be disassembled if they are to be moved from one location to another. This is their main limitation.

Elevators and lifts are used to raise everything from materials to workers. Since moving materials on this type of equipment is quite costly, the modern trend is to construct one storey plants, thus eliminating the need to raise and lower material between floors.

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JOB SEQUENCING


83

JOB SEQUENCING - ILLUSTRATIONS

Job sequencing is concerned with appropriate selection of a sequence of jobs to be done on a finite number of service facilities (like machines) in some well-defined technological order so as to optimize total elapsed time or overall cost.

• Determine the optimum sequence to process the various types of fan blades each day from the following information so as to minimize the total elapsed time.

Also work out the total elapsed time for an optimism sequence. What is the total machine time on machine-A and machine-B?

Type of fan blades

Number to be

processed each day

Machine A

(minutes)

Machine B

(minutes)

1 4 4 8

2 6 12 6

3 5 14 16

4 2 20 22

5 4 8 10

6 3 18 2

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• In a machine shop 8 different products are being manufactured, each requiring time on the two machines ‘A’ and ‘B’ as given below:

Determine the optimum sequence to minimize the total manufacturing time for all the products.

Product Time in minutes

on machine-A

Time in minutes

on machine-B

1 35 20

2 45 30

3 15 50

4 20 35


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• We have five jobs each of which must go through three machines A, B and C in the order ABC. Processing time in hours is as given below:

Determine a sequence for the five jobs that will minimize the total elapsed time. Find also the idle time of the machines A, B and C.

Job A B C

1 16 10 8

2 20 12 18

3 12 4 16

4 14 6 12

5 22 8 10


86

• Find an optimum sequence for the following sequencing problem of four jobs and five machines. The processing time in hours is given below:

Also find total elapsed time.

Job A B C D E

1 7 5 2 3 9

2 6 6 4 5 10

3 5 4 5 6 8

4 8 3 3 2 6


87

METHOD STUDY


88

METHOD STUDY

Method Study and Work Measurement are the two basic techniques of work study. While Method Study aims to improve the existing methods of operations and procedures, work measurement helps to assess the human effectiveness. Though these two are distinctly separate techniques, they are very much interdependent. The application of both these techniques in adequate proportions based on the nature and type of problems would result in maximum benefits to the organisation.

Method Study is essentially concerned with finding better ways of doing work. It is a technique of cost reduction. The philosophy of Method Study is, “there is always a better way” and the tools of Method Study are designed to systematically arrive at this “better way of doing a job”. Method Study can be applied to almost all types of work, whether it be a factory, electrical or any other type of activity. The scope of Method Study is not restricted to manufacturing industries alone, but extends to all other spheres. Methods improvement has been very successfully adopted in banks, hospitals, offices and retailing, in addition to defence, agriculture and all types of industries. There are various techniques which are suitable for tackling Method Study problems on all scales and for all types of work. There is no limit to the types of work which can be profitably studied. Another important aspect of Method Study is that often, with limited capital expenditure, it would be possible to obtain considerable economies in the use of resources and achieve large monetary savings.

89

METHOD STUDY

Method Study is the systematic recording and critical examination of existing and proposed ways of doing work, as a means of developing and applying easier and more effective methods and reducing costs. (Definition adopted in the B.S.Glossary of terms in Work Study.)

OBJECTIVES

The objectives of Method Study are – i) Improve basic processes.

ii) Improve the design of plant and equipment.

iii) Improve factory, office and work place layouts and handling of materials.

iv) Improve the use of material, plant, equipment and power.

v) Improve the working procedures.

vi) Improve the working environment.

vii) Improve quality.

90

METHOD STUDY

METHOD STUDY PROCEDURE

The analysis of problems for Method Study consists of an ordered and systematic procedure. This procedure involves six basic steps as follows:

SELECT the work to be studied

RECORD all relevant facts

EXAMINE these facts critically

DEVELOP the most effective, economical and practical method

INSTALL the method as standard practice

MAINTAIN the standard practice by regular checks

The above procedure is a logical one and is easy to follow in any type of work. Each of the steps is equally important and clearly defined. Faithful adherence to the basic procedure would result in achieving maximum results.

91

METHOD STUDY

Selection of work for Method Study is the first step. The field of choice for Method Study is quite wide and every job is amenable to improvement. But the selection of the job should be based on scope and need for improvement, resulting economy, priority, objective and similar other considerations. Once the job has been selected, the next step is to record all the pertinent facts relating to the present or proposed method. There are a variety of recording techniques suitable for different types of situations. A proper recording is necessary since it forms the basis for further investigation. Critical examination is the crux of Method Study. All these recorded facts are subjected to a thorough examination. Nothing is taken for granted and each activity is challenged with a view to get as many alternatives and improved methods as possible. All the alternative proposals thus obtained are evaluated and the most practical and economical method is developed. Considerable planning and preparation is necessary before the proposed method is installed. Full cooperation and participation from the Management, Supervisors and workers is essential for the implementation of the new method. A number of difficulties may crop up when the proposed method is under operation. There is also a tendency on the people to get back to the old methods with the slightest of excuses. Proper maintenance through routine and regular checks is an important factor in the Method Study procedure.

92

QUALITY CONTROL & INSPECTION


93


It is important that production process meets the quantity goals established in the production schedule, but it is of equal importance that the output meets the quality specifications as well. To manufacture products of desired quality, control over their quality must be exercised throughout the production and associated functions, including production planning, procurement and distribution. Quality considerations are present in every aspect of the production cycle – from the purchase of raw material to the customer.

Monitoring all the quality level is usually assigned to a staff group that reports to the top management. Organisationally, this group is commonly referred to as Quality Control. The authority that quality control exercises varies according to the relative defect of controlling quality and to management assessment of the consequences of circulating the defective products.

Since quality assurance enters into so many linkages within the production system, more support is needed from all levels of management than for most of the functions. No single department or staff can assure quality by itself. It takes cooperation of line workers, the supervisors and related staff organisation.

Quality assurance is a skill. Like other skills, if it is not continuously exercised, it will deteriorate. Also, it has been said that “quality is everybody’s concern.” But a job that belongs to everybody can easily become a job that nobody does.

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The overall value of the quality organisation should be judged by the ratio of cost incurred to cost saved, and not by the glamour of its own advertisements.

Cost of vigilance versus cost of error: In most production situations, the cost of vigilance and error varies inversely. Greater vigilance may take the form of extra time taken by individual worker, close supervision, additional test for products and inspection of all or portion of the output. The cost of error includes re-work, rejects and customer dissatisfaction. Somewhere between the extremes of no vigilance and extra vigilance is a point where control over the magnitude of errors produces a minimum total cost.

Inspection versus quality control: Inspection is an act of comparing a product with accepted specifications or other recognized standards. The purpose of this inspection is to know where the product conforms to or does not conform to the specified quality limits expressed in the specifications. Units of the product found to conform are accepted; others are rejected.

Inspection is essentially a post-mortem operation performed on the product after it has been completely processed. As a screen operation, the purpose of inspection is to separate products into two classes: accepted and not accepted.

Inspection operation itself adds nothing to the value of the product. Hence, the inspection operation itself does not improve product quality and neither does it reduce rejections, since it involves no corrective action on the operation.

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The problem is, how to guarantee a product of high quality to the customer and not burden the manufacturer with the loss of high percentage of rejections entailed by the inspection screening operation. The answer to this lies in quality control.

Quality control is a system of inspection, analysis and action applied to a manufacturing process so that by inspecting a small portion of the product currently produced, an analysis of its quality can be made to determine what action is required on the operation to achieve and maintain the desired level of quality. In its broader application, quality control is a preventive tool and is used to minimize rejections to the end that all products and processes will meet the specified quality limits.

When and where and how to inspect: Where to inspect depends largely on when the inspection is scheduled. The location of most inspection stations is at the site of production – the receiving dock for incoming shipments, the assembly area, the construction site, distribution points, etc. In a fixed-position layout, inspectors must come to the product to check quality at various stages of development. In product layouts, particularly mechanized production lines, products come to the inspectors at special stations built into the line. Receiving “floor inspectors” examine output from the individual work stations associated with a process layout.

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Deciding where to inspect during a production process is simply a matter of common sense – when it will do the most good. Logical choices are the beginning and end of the production process. Raw material and component inputs should be inspected to see whether they meet expected standards. Acceptance of substandard inputs obviously jeopardizes outgoing quality and may damage equipment or disturb process continuity. Outgoing products are examined to protect the producer from customer discontent or buyer rejection.

During the production process, inspection is scheduled in front of operations that are costly, irreversible or masking. Considerable expense is avoided by eliminating defective units before they undergo a costly phase of their development or before they pass through a process that cannot be undone, such as welding, pouring concrete, or mixing. Chemical operations such as painting and encapsulating may hide defects easily detectable before the masking operation.

From the foregoing, it may appear that products are continually under inspection. Actually, workers continually check the quality of their own or a machine’s output, but there are just a few distinct inspection stations. Constant formal surveillance would not only increase cost, it would also create an uncomfortable atmosphere for workers. The timing and location of inspection points are key features in the design of any testing programme.

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How to inspect: The two basic types of inspection are called “variables” and “attribute”. When precise measurements are made of dimensions, weight or other critical characteristics capable of expression on a continuous scale, the products are being subjected to variables inspection. The alternative to exact measurements is to set limits within which the product is judged acceptable or defective. A go-no-go rating results from an attribute inspection. Since a good or bad grading normally requires less time and skill to make and uses lower-cost equipment than exact measurements, attribute inspection is usually less expensive than variables inspection. It is generally assumed that the variables measured have a normal distribution.

Precise measurements require closely calibrated devices, rulers, micrometers, scales, meters, etc., capable of measuring the product’s fineness standard. Devices to check attributes are designed to provide a quick verdict of acceptability – go-no-go gauges, snap gauges, templates, etc.

Statistical sampling techniques frequently reduce inspection cost. The use of samples to replace 100% inspection is usually appropriate for machine output where units are not so likely to vary as are hand-crafted products. High production quantities and expensive inspections also suggest sampling. Then there is destructive testing (the performance test destroys the unit tested) which absolutely rules out 100% inspection.

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Acceptance sampling: The purpose of acceptance sampling is to recommend a specific action; it is not an attempt to estimate quality or to control quality directly. The basic action recommended is to accept or reject the items represented by the sample. The sampling plan specifies the sample size and the associated number of defectives that cannot be accepted without rejecting the lot from which the sample was taken. In its simplest form, the quality of a certain number of products of the same type is measured by drawing a random sample from the lot. The sample is tested, on which basis the entire lot is either accepted or rejected on the basis of the quality of the sample. The rejected lots may then be inspected 100%.

In sampling, accepting a bad lot is termed as consumer’s risk whereas rejecting a lot with fewer defectives than the standard, is termed as producer’s risk.

Limitations of acceptance sampling:

Since the conclusion is based on a sample, there is always some likelihood / risk of making a wrong inference about the quality of the lot.

The success of the scheme depends on the randomness of the samples, quality characteristics to be tested, lot size, acceptance criteria, etc.

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Statistical Quality Control

Statistical Quality Control is applied by taking samples and drawing conclusions by means of some mathematical analysis. It has already been explained in a previous section that variation in the quality of the product is an inherent characteristic of a manufacturing system. Irrespective of all possible precautions and quality measures there are always a large number of random disturbances responsible for deviations in the quality of the product from the set standards. The sources of these disturbances are known as chance causes. For example, movement of the machine due to passing traffic, sudden changes in temperature etc. The presence of these causes in the system is due to a multitude of reasons which are difficult to identify and uneconomical to eliminate. These can neither be discerned or removed. There is very little that we can do about these.

Various sampling plans:

Single sampling plan.

Double sampling plan.

Sequential sampling plan.

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There may be other sources of variations in a system which further cause the product to deviate from set standards. These individual causes can be identified and eliminated economically. The magnitude of variability due to these causes varies with the conditions of the production process, nature of the raw material, behaviour of operations etc. These causes are known as assignable causes. The reasons for the presence of assignable causes can be (i) differences among workers performance (ii) differences among machines (iii) variation in material and (iv) variation due to the interaction of any two or all the three factors e.g. tool wear, errors in setting poor machine maintenance etc.

The chance and assignable causes combine together to lower the quality of the product. Any item which is not in accordance with the quality specifications is known as defective item and is liable to be rejected by producer and consumer. The object of quality control is to minimize the proportion of defectives in the given lot.

Inspection is the method of locating defective items by examining these against specifications and statistical quality control is to ascertain whether the variation in the quality of the product is due to chance causes or due to assignable causes. If the process is found to be in statistical control then it indicates that the variation in the quality is due to chance causes only; otherwise presence of assignable causes is detected and some corrective action is planned to improve the quality of the product. Control charts are the basis of Statistical Quality Control technique.

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Benefits of Statistical Quality Control:

• The use of statistical quality control ensures rapid and efficient inspection at a minimum cost.

• It minimizes waste by identifying the causes of excessive variability in the quality of product.

• SQC exerts more effective pressure for quality improvement than 100% inspection.

Control Charts :

A Control Chart is a graphical aid for depiction of quality variation in output from a production process. As opposed to the aim of acceptance sampling (to reject or accept products already produced), control charts aid in the production of a better product. The charts have three main applications:

• To determine the actual capability of production processes.

• To guide modification to improve the output of the processes.

• To monitor the output – wherein the current status of the output quality provides an early warning of deviations from the quality goals.

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SAFETY


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SAFETY

Safety should be there for workers – Humanitarian.

Safety should not affect productivity. Safety should be there for machines and for the operation of the machines.

Take the example of a press operated by an operator, putting the material with hands, with the operating buttons at the bottom (operated by the leg). If the synchronism between the hand and leg misses, there could be an accident.

Types of accidents that could occur:

• Fatal accident: This is the most expensive accident for the factory and the worker. The factory loses a skilled worker as well as the money for compensation.

• Major accident: Any part of the body is lost, whether the person is hospitalized or not. The victim of the accident may become permanently disabled, necessitating his absence from work over a period of time. This is known as “lost time accident”.

• Minor accident: No part of the body is lost but injured.

• No injury accident: Accident has occurred but the worker is not injured.

• Dangerous occurrence: For example, gas leakage which has not caused accident but is potentially dangerous if timely collective remedial action is not taken.

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SAFETY

How does an accident occur?

• Unsafe conditions

• Unsure act

Whenever any or all of the following four factors come into play, an accident can occur:

1) Personnel factor – person/s should be present.

2) Material factor – equipment should be present.

3) Unsafe action factor – this act would have been forced by the process employed or by the machine design.

4) Proximate casual factor –

2) + 3) + 4) without 1) will lead to dangerous occurrence.

For example, stepping on the defective step of a ladder. First, the three will be met and

after they combine with 4), the accident will occur.

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SAFETY

Accident Prevention Principles

There are 12 principles:

• Planning:

Examples– plant layout less material handling. The following factors can prevent accidents:

A scientific plant layout.

Process sheet planning.

Safe access to machine or job

Adequate space around the machine and jobs.

Broad walkways, no cross-hauling of material handling equipment

Isolate the dangerous areas. Example: Forging, smelting furnaces, paint booths. Accident preventors are –

Mask

Water-curtain

Air-curtain

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SAFETY

• Design:

Design has to incorporate safety devices. For example, machine guard. Machine guard should be such that it should –

hinder the work;

be able to prevent the work;

be able to withstand wear and tear;

allow for easy maintenance and lubrication of machine. A scientific plant layout.

Another example of accident prevention: Safety clutch in gun.

• Training and Education:

The operator and supervisor should be given proper training and they should be taught about the need or the necessity of safeguards. If the supervisor is not educated, the worker may invariably complain of unsafe working condition.

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SAFETY

• Fire protection:

You must have means for fire protection. Some areas may be “non-smoking” areas. Fire-prevention and fire-fighting equipment like fire alarms should be kept.

• Good house-keeping:

You must have means for fire protection. Some areas may be “non-smoking” areas. Fire-prevention and fire-fighting equipment like fire alarms should be kept.

• Working clothes:

Clothes should not be loose fitting and there should be no loose ends, e.g., ties etc. Long beards should not be allowed.

• Colour code to identify accident-prone areas:

Orange/yellow: Area with many moving parts/objects.

Red: Out-of-bounds area where the risk of an accident is very high.

Green: No problem area.

Yellow & black stripes: e.g., railway crossings, road crossings, etc., where accidents can be avoided by being alert. hinder the work;

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SAFETY

• Notice boards / sign boards, with instructions:

While colour code is meant for a fair general area, for a particular machine a notice board should be prominently displayed highlighting the nature of the potential danger and the preventive safety measures.

• Labels: Same as above.

• Lighting: should be adequate and uniform.

• Control of noise – volume, sub-sonic and ultrasonic frequencies - temperature and proper ventilation.

• Others:

1. First-aid.

2. Proper escape routes in the event of an accident.

Production Management

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