Manufacturing process, Lecture notes of Manufacturing Processes

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INTRODUCTION TO MANUFACTURING PROCESSES

Manufacturing Processes for Engineering Materials by S.

Kalpakjian (fifth edition)

GENERAL INFORMATION

 One Hour Class Tests

 Quizzes

 Project/Presentation

 Final

 Minimum Attendance Required: 75%

 Course Material: 1. Lecture Slides

2. Reference Books

3. Internet

A ballpoint pen for example consists of dozens of parts, a typical automobile 15,000 parts and a Boeing 747 about 6 million parts. All are produced by a combination of various processes called Manufacturing.

ABSTRACTION OF MANUFACTURING PROCESSES

PARTS

A part is a designed object that has no assembly operations in

its manufacture. Parts may be made by a sequence of

manufacturing processes (e.g., casting followed by milling), but

parts are not assembled.

Parts are either standard or special purpose. A standard part

is a member of a class of parts that has a generic function and is

manufactured routinely without reference to its use in any

particular product. Examples of standard parts are screws, bolts,

rivets, buttons, most beams, gears, springs, and washers.

Special purpose parts are designed and manufactured for a

specific purpose in a specific product or product line rather than

for a generic purpose in several different products.

ASSEMBLY AND SUBASSEMBLY An assembly is a collection of two or more parts. A subassembly is an assembly that is included within an assembly or other subassembly. A standard assembly is an assembly or subassembly that like a standard part has a generic function and is manufactured routinely for general use or for inclusion in other subassemblies or assemblies. Examples of standard assemblies are electric motors, heat exchangers, pumps, gear boxes, light bulbs, etc Assembly is an important phase of the overall manufacturing operation and requires considerations of the ease, speed and cost of putting parts together.

MANUFACTURING PROCESSES SELECTION

Selection of a particular manufacturing process or a

series of processes depends not only on the part shape

to be produced but involves other factors such as;

1. Material properties (brittle and hard materials for example

cannot easily be shaped/formed but they can be cast or machined by various methods)

2. Distinct ranges (manufacturing processes have distinct ranges

of product size, shape and thickness which needs to be compared with the requirements of the product)

3. Accuracy (Each process has its own characteristic precision,

accuracy and surface finish etc)

MANUFACTURING PROCESSES SELECTION

4. Operational costs (design and cost of tooling, the lead time

and the effect of workpiece materials on tool and die life are important factors)

5. Production rate (The quantity of parts required and the desired

production rate (piece per hour) help to determine the manufacturing process to be used)

6. Environmental concerns (Depending on the type of

operation and the machinery involved some manufacturing processes adversely affect the environment)

GRAIN AND GRAIN BOUNDARIES

A block of metal may contain millions of individual

crystals, called grains.

The number and the size of the grains in a unit volume of

the metal depends on the rate of which nucleation (the

initial stage of formation of crystals) takes place. Rapid

cooling produces smaller grain, whereas slow cooling

produces larger grains.

The surfaces that separate the individual grains are

called grain boundaries.

GRAIN AND GRAIN BOUNDARIES

The number of different stages in which individual

crystals begin to form is shown in Fig 1.

Fig 1: (a) Small square represent unit cell. (b) Nucleation of crystals at random sites in the molten metal (c) Growth of crystals as solidification continues and (d) Solidified metal, showing individual grains and grain boundaries.

PROPERTIES OF MATERIAL

Following are some basic mechanical properties of material:

1. Tension

2. Compression

3. Bending

4. Hardness

5. Fatigue

6. Creep

Product with high quality should provide following characteristics; Performance: The basic operating characteristics of a product; for example, how well a car handles its gas mileage. Features: The "extra" items added to the basic features, such as a stereo CD or a leather interior in a car. Reliability: The probability that a product will operate properly within an expected time frame or the measure of confidence of a consumer towards a particular product. Eg. a Sony TV will work without repair for about seven years. Conformance: The degree to which a product meets pre-established standards. There should be an agreement between the designed and the actual product standard / specifications. E.g. Descon made pressure vessel fails in few days is non- conformance. PRODUCT QUALITY

There are four ways in which the market can be served: Make to Stock (MTS): In this case, the customer requires product with almost no forward notice. Suppliers usually manufactures in anticipation of demand and maintain stock of finished product. E.g. stationary, cold drinks, lays chips etc Configure to Order (CTO): In this case, customer is prepared to wait for limited period but not long enough for the product to be manufactured from base raw materials. Company usually configures components into saleable products when actual customer order are received. E.g. car industry, ordering food in a restaurant Make to Order (MTO): In this case, company does not commit resources until firm customer order have been received. E.g. manufacturing of commercial and fighter airplanes Engineer to Order (ETO): This is similar to MTO except that in this case, the item to be manufactured is defined by the customer. E.g. customised Ferrari or Rolls Royce or private airplane, tailored clothes etc MEANS OF SERVING THE MARKET

PRODUCT LIFE CYCLE (PLC)

A product is "anything that is capable of satisfying customer

needs”.

This definition includes both physical products (e.g. cars,

washing machines, DVD players) as well as services (e.g.

insurance, banking, private health care).

Businesses should manage their products carefully over time

to ensure that they deliver products that continue to meet

customer wants.

The stages through which individual products develop over

time is known as the "Product Life Cycle".