1.1 Introduction to Manufacturing Process and their classification

Unit - 1

Introduction to Manufacturing Process

Manufacturing process is that part of the production process which is directly concerned with the change of form or dimensions of the part being produced.

Fig1. Classification of Manufacturing Processes

The manufacturing processes can be classified as:

1. Forming Processes

2. Moulding Processes

3. Machining Processes

4. Assembly Processes

5. Finishing Processes

1. Forming Processes:

In the metal industry, some of the primary forming operations may take place such as the rolling of basic shapes in steel, aluminium etc. Some of the common shapes so obtained from these processes are bars, sheets, billets, I-beams etc. Which are standard shapes. These shapes can be used for further processing. Other forming processes may be drop-forging, stamping, extrusion, press work, punching, drawing etc.

2. Moulding Processes:

Some products require moulding processes such as sand casting, die-casting etc. to get basic shape or form which may or may not require further processing. The selection of the particular process will depend upon to size of the job, quantity to be produced, accuracy, and complexity desired and economy.

3. Machining Processes:

Metal machining is accomplished through basic machine tool processes which involve the generation of cylindrical surfaces, flat surfaces, complex curves and holes. The machine tools selected to accomplish this task depend on the size and shape of the part to be machined, the quality of finish required and production rate required.

The examples of such processes are: turning, shaping, drilling, boring, grinding etc. In these machining operations metal is removed from the part in the form of small chips by the cutting action of tool. The cutting action is accomplished by either rotating or reciprocating action of the tool relating to the part.

4. Assembly Processes:

These processes assemble the parts and materials using welding, riveting, soldering, brazing, mechanical fastening and adhesive joining etc.

5. Finishing Processes:

These processes are carried out for the aesthetic aspects, to achieve accuracy, surface finish or to increase life of the product. Such processes include cleaning, blasting, deburring, puffing, honing, lapping, polishing, painting etc.

1.2 Automation in Manufacturing

Automation can also be defined as the process of following a predetermined sequence of operations with little or no human intervention, using specialized equipment and devices that perform and control the manufacturing process.

1.3 Industrial Safety

1.3.1 Introduction

Industrial safety is primarily a management activity which is concerned with:

Reducing

Controlling

Eliminating hazards from the industries or industrial units.

Objectives of Industrial Safety:

To prevent accidents in the plant by reducing the hazard to minimum.

To eliminate accident caused work stoppage and lost production.

To achieve lower workmen’s compensation, insurance rates and reduce all other direct and indirect costs of accidents.

To prevent loss of life, permanent disability and the loss of income of worker by eliminating causes of accidents.

To evaluate employee’s morale by promoting safe work place and good working condition.

To educate all members of the organization in continuous state of safety mindless and to make supervision competent and intensely safety minded.

1.3.2 Types of Accidents

An unplanned and uncontrolled event in which the action or reaction of an object, substance, person, or radiation results in personal injury or the probability thereof.

Industrial accidents refer to any accident that occurs at an industrial site.

Technical Causes:

Unsafe condition

Mechanical factors

Environment factors

2. Human Causes:

Unsafe acts

Personal factors

3. Mechanical causes:

Design

Arrangement

Guarding

Apparel

Devices

Handling

1.3.3 Causes and Common Sources of Accidents

Causes of Industrial Accidents are:

1. Unsafe conditions: The causes of industrial accident that pertain to unsafe conditions may include insufficient workplace lighting, excessive noise, slippery or unsafe flooring, extreme temperature exposure, inadequate protection when working with machinery or hazardous materials, unstable structures, electrical problems, machine malfunction or failure and so on.

a. The job itself

b. Work schedules

c. Psychological conditions

d. Machinery & Equipment

2. Unsafe Acts: The causes of industrial accidents that pertain to unsafe acts may include actions or failures to act which results in injury.

3. Miscellaneous Causes

1.3.4 Methods of Safety

1. Safety Policy

2. Safety Committee

3. Safety Engineering

a. Guarding of machinery

b. Material handling equipment

c. Safety devices

d. Ergonomics

e. Plan maintenance

f. General house keeping

4. Safety Education & Training

5. Role of Government

1.3.5 Electric Safety Measures

Do plug power equipment into wall receptacles with power switches in the Off position.

Do unplug electrical equipment by grasping the plug and pulling. Do not pull or jerk the cord to unplug the equipment.

Do not drape power cords over hot pipes, radiators or sharp objects.

Temporary or permanent storage of any materials must not be allowed within 3 feet of any electrical panel or electrical equipment.

Do check the receptacle for missing or damaged parts.

Do not plug equipment into defective receptacles. Do check for frayed, cracked, or exposed wiring on equipment cords.

Employees should know the location of electrical circuit breaker panels that control equipment and lighting in their respective areas. Circuits and equipment disconnect must be identified.

Do check for defective cords clamps at locations where the power cord enters the equipment or the attachment plug.

Extension cords should not be used in office areas. Generally, extension cords should be limited to use by maintenance personnel “Cheater plugs”, extension cords with junction box receptacle ends or other jury-rigged equipment should not be used.

1.4 First Aid

The initial process of assessing and addressing the needs of someone who is experiencing medical emergencies.

Allows a “non-medical expert” to quickly determine a person’s physical condition and the course of treatment.

Can make a difference to a person’s recovery and could save their life.

Purpose of First Aid:

To Sustain the life

To Prevent suffering

To Prevent secondary complications

To Promote speedy recovery

1.5 Plant Layout

Plant layout refers to the arrangement of physical facilities such as machinery, equipment, furniture etc. within the factory building in such a manner so as to have quickest flow of material at the lowest cost and with the least amount of handling in processing the product from the receipt of material to the shipment of the finished product.

1.6 Principles of Plant Layout

Principle of Plant Layout are as follows:

1.Principle of Minimum Movement:

As far as possible materials and labour should be moved over minimum distances.

2.Principle of Flow:

The work areas should be arranged according to the sequence of operations so that there is continuous flow of materials without congestion.

The layout should allow for easy movement of materials without interruption or delay.

3.Principle of Space:

All available cubic space should be effectively used both vertically and horizontally.

4.Principle of Safety:

There should be consideration for safety and convenience of workers.

There should be built in provision for the safety and comfort.

5.Principle of Flexibility:

Layout should be designed in the manner that production facilities can easily be rearranged when it becomes necessary in future on account of expansion and technological advancement.

6.Principle of Interdependence:

Interdependent operations and processes should be located in close proximity to each other.

7.Principle of Overall Integration:

All the plant facilities and services should be fully integrated into a single operating unit so as to maximize efficiency and minimize costs of production.

8.Principle of Minimum Investment:

The layout should yield savings in fixed capital investment through optimum utilization of available facilities.

1.7 Types of Plant and shop layouts and their Advantages

Types of Plant Layouts:

1. Product or Line Layout

2. Process or Functional Layout

3. Fixed Position or Location Layout

4. Combined or Group Layout

1. PRODUCT OR LINE LAYOUT:

Under this, machines and equipment’s are arranged in one line depending upon the sequence of operations required for the product. The materials move from one workstation to another sequentially without any backtracking or deviation. Under this, machines are grouped in one sequence. Therefore, materials are fed into the first machine and finished goods travel automatically from machine to machine, the output of one machine becoming input of the next.

e.g., in a paper mill, bamboos are fed into the machine at one end and paper comes out at the other end. The raw material moves very fast from one workstation to other stations with a minimum work in progress storage and material handling.

The grouping of machines should be done keeping in mind the following general principles.

a) All the machine tools or other items of equipment’s must be placed at the point demanded by the sequence of operations.

b) There should no points where one line crossed another line.

c)All the operations including assembly, testing, packing must be included in the line.

Fig2. Use of repetitive or continuous processing

ADVANTAGES OF PRODUCT LAYOUT:

1. Low cost of material handling, due to straight and short route and absence of backtracking.

2. Smooth and uninterrupted operations.

3. Continuous flow of work.

4. Lesser investment in inventory and work in progress.

5. Optimum use of floor space.

6. Shorter processing time or quicker output.

7. Less congestion of work in the process.

8. Simple and effective inspection of work and simplified production control. 9. Lower cost of manufacturing per unit.

DISADVANTAGES OF PRODUCT LAYOUT:

1. High initial capital investment in special purpose machine

2. Heavy overhead charges

3. Breakdown of one machine will hamper the whole production process

4. Lesser flexibility as specially laid out for particular product.

2. PROCESS OR FUNCTIONAL LAYOUT:

In this type of layout machines of a similar type are arranged together at one place. E.g., Machines performing drilling operations are arranged in the drilling department, machines performing casting operations be grouped in the casting department. Therefore, the machines are installed in the plants, which follow the process layout.

The work, which has to be done, is allocated to the machines according to loading schedules with the object of ensuring that each machine is fully loaded.

Used when the operations system must handle a wide variety of products in relatively small volumes (i.e., flexibility is necessary)

The grouping of machines according to the process has to be done keeping in mind the following principles –

1. The distance between departments should be as short as possible for avoiding long distance movement of materials.

2.The departments should be in sequence of operations

3.The arrangement should be convenient for inspection and supervision.

Fig3. Process layout

ADVANTAGES OF PROCESS LAYOUT:

1. Lower initial capital investment in machines and equipment’s. There is high degree of machine utilization, as a machine is not blocked for a single product.

2. The overhead costs are relatively low

3. Change in output design and volume can be more easily adapted to the output of variety of products.

4. Breakdown of one machine does not result in complete work stoppage

5. Supervision can be more effective and specialized.

6. There is a greater flexibility of scope for expansion.

DISADVANTAGES OF PROCESS LAYOUT:

Material handling costs are high due to backtracking.

More skilled labour is required resulting in higher cost.

Time gap or lag in production is higher

Work in progress inventory is high needing greater storage space.

More frequent inspection is needed which results in costly supervision

3. FIXED POSITION OR LOCATION LAYOUT:

In this type of layout, the major product being produced is fixed at one location. Equipment labour and components are moved to that location. All facilities are brought and arranged around one work center. This type of layout is not relevant for small scale entrepreneur.

E.g. – shipbuilding

Fig 4. Fixed – Position Layout

ADAVANTAGES OF FIXED POSITION LAYOUT:

1. It saves time and cost involved on the movement of work from one workstation to another.

2. The layout is flexible as change in job design and operation sequence can be easily incorporated.

3. It is more economical when several orders in different stages of progress are being executed simultaneously.

4. Adjustments can be made to meet shortage of materials or absence of workers by changing the sequence of operations.

DISADVANTAGES OF FIXED POSITION LAYOUT:

Production period being very long, capital investment is very heavy.

Very large space is required for storage of material and equipment near the product.

As several operations are often carried out simultaneously, there is possibility of confusion and conflicts among different workgroups.

4. COMBINED OR GROUP LAYOUT:

Certain manufacturing units may require all three processes namely intermittent process (job shops), the continuous process (mass production shops) and the representative process combined process.

In most of industries, only a product layout or process layout or fixed location layout does not exist. Thus, in manufacturing concerns where several products are produced in repeated numbers, Generally, a combination of the product and process layout or other combination are found in practice.

e.g., for industries involving the fabrication of parts and assembly, fabrication tends to employ the process layout, while the assembly areas often employ the product layout.

In soap, manufacturing plant, the machinery manufacturing soap is arranged on the product line principle, but ancillary services such as heating, the manufacturing of glycerine, the power house, the water treatment plant etc. are arranged on a functional basis.