introduction tomanufacturing processes 26 04 2011

Introduction to Manufacturing Process

Dr.R.ANAND, Assistant Professor

Department of Mechanical EngineeringNational Institute of Technology-Trichy

Introduction• Most of the products that we use in our day-to-day life do not occur by

nature in their present form and dimension. • We require some raw materials from which those products are

manufactured or produced. • There are various processes available to transform the raw material into

its final shape and dimensions. • These processes that the industries use to convert the raw materials into

their finished products are called Production processes or Manufacturing processes.

• They include not only the physical processes associated with transforming the shape of the raw materials but also the allied processes like process planning, production control, assembly and quality assurance.

Machining Processes:In machining processes, the required shape and dimensions of the final component is obtained by removing the unwanted parts of the raw material in the form of chips.

Casting Processes:In casting processes, the required shape and dimensions of the final component is obtained by pouring the molten material into a mold cavity where, upon solidification, it takes the shape of the cavity.

 Forming Processes:

In forming processes, the required shape and dimensions of the final component is obtained by deforming the raw material.

Engineering materials

• Material selection is one of the important step in engineering design.

• Study about the properties of material is required to select the proper material.

Classification of engineering materials

Classification of materials

1. Metals2. Non-metals3. Composites

Metals1. Ferrous – (Pure iron + carbon)– Cast Iron– Carbon and Alloy steel– Stainless steel– Tool and Die steel

2. Non-ferrous – Aluminium and its alloys– Copper and its alloys– Titanium and its alloys – Magnesium and its alloys

FERROUS METALS

• Ferrous metals are wrought iron (with less than 0.2% carbon), cast iron (with 3.5-5% carbon), steel (with 0.1-1.2% carbon).

• They may also be alloys of iron and other elements. • Ferrous alloys are the most commonly used engineering materials. Its density is

around 7800 kg/m3.

Cast Iron:• Carbon is present in Cast Iron in the free form and it is usually present in the range of 1.8% to 4.5%.

In addition, silicon, manganese, sulphur and phosphorus are also contained in varying amounts.  Depending upon the form of carbon present, several types of cast iron are obtained. These include

– Gray Cast Iron, – White Cast Iron, – Chilled Cast Iron & Ductile Cast Iron (Nodular Cast Iron), – Malleable Cast Iron

Carbon Steels• Plain carbon Steels are alloys of Iron and Carbon. They are further classified as

– Low carbon steel (upto 0.30% C) – Medium carbon steel (0.30 to 0.60%) – High carbon steel (above 0.60% C)

• Alloy Steels:– Steels that contain nickel, chromium, cobalt, vanadium etc. apart from carbon as

alloying elements are called as alloy steels.• Stainless Steels:

– It contains at least 10% chromium, with or without other elements. Based on the structures, stainless steels can be grouped into three grades:

– Austenitic: Typically contains 18% chromium and 8% nickel and is widely known as 18-8.

– Ferritic: Contains very little nickel and either 17% chromium or 12% chromium with other elements such as aluminum or titanium.

– Martensitic: Typically contains 12% chromium and no nickel. • Ferritic and martensitic stainless steels are usually classified as magnetic and austenitic

stainless steels non-magnetic.

• Tool and Die Steels:– Tool and die steels are specially alloyed steels. – They are designed for high strength, toughness (resistance to impact) and wear

resistance at room and elevated temperatures.

FERROUS METALS

NONFERROUS METALS – Nonferrous metals and alloys cover a wide range of materials, from the

more common metals such as aluminium, copper and magnesium to high-strength, high-temperature alloys such as those of tungsten, titanium, tantalum and molybdenum.

• Aluminium and its alloys:– The main reason in selecting aluminium and its alloys are their high strength-

to-weight ratio, their resistance to corrosion for many chemicals, their high thermal and electrical conductivity, reflectivity and appearance and their ease of formability and machinability. Its density is around 2700 kg/m3

.

– Aluminium alloys can be divided into two major groups depending on their method of fabrication:• Wrought alloys, which are shaped by plastic deformation• Casting alloys, which are made by casting process

– The uses of aluminium and its alloys are in containers and packaging (aluminium cans and foils) and in transportation (aircraft and aerospace applications, automobiles and marine craft)

NONFERROUS METALS• Copper and its alloys: 

Copper and its alloys have properties somewhat similar to those of aluminium and its alloys. In addition, they are among the best conductors of electricity and heat and they have good corrosion resistance.

– Brass, which is an alloy of copper and zinc and has numerous applications, including decorative objects

– Bronze, which is an alloy of copper and tin having good strength and hardness for applications such as bearings etc

 • Titanium and its alloys: 

– Titanium and its alloys have excellent corrosion resistance for applications where strength considerations are secondary.

– Aluminium, vanadium, molybdenum, manganese and other alloying elements are added to titanium alloys to impart properties such as improved workability, strength and hardenability.

 • Magnesium and its alloys:

Magnesium is the lightest engineering metal and it has good vibration damping characteristics. Its alloys are used in structural and non-structural applications wherever weight is of primary importance.

Magnesium alloys are used in aerospace applications, high-speed machinery, and transportation and materials handling equipment.

NONFERROUS METALS• Plastics:

Plastics are materials that are composed principally of naturally occurring and modified or artificially made polymers often containing additives such as fibres, filler, pigments and the like that further enhance their properties.

  Plastics include thermoplastics, thermoset materials and elastomers.

• Ceramics: A ceramic is often broadly defined as any inorganic non-metallic material.

Some of the useful properties of ceramics and glasses are high melting temperature, strength, stiffness, hardness, wear resistance and corrosion resistance and low density.

• Composites: Composites are formed from two or more types of materials. Examples include

polymer/ceramic and metal/ceramic composites. Since the overall properties of the composites in the required orientations are superior to those of the individual constituents, they are widely used for many engineering applications.

Classifications of manufacturing processes

Manufacturing Processes1. Casting2. Forming

i. Forgingii. Rollingiii. Extrusioniv. Drawing

3. Metal joiningi. Welding – Gas, Arcii. Brazingiii. Soldering

4. Machiningi. Latheii. Drillingiii. Milling

Casting

• Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify.

• The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process.

• Casting is most often used for making complex shapes that would be otherwise difficult or uneconomical to make by other methods.

Patterns

• Patterns in sand casting are used to form the mold cavity. One major requirement is that patterns (and therefore the mold cavity) must be oversized – to account for shrinkage in cooling and solidification, and – to provide enough metal for the subsequence machining operation(s)

Basic production steps in sand casting

Foundry sands

• The typical foundry sand is a mixture of fresh and recycled sand, which contains 90% silica (SiO2), 3% water, and 7% clay.

• The grain size and grain shape are very important as they define the surface quality of casting and the major mold parameters such as strength and permeability.

Casting method - moulding

Casting process – Pouring of molten metal

Wax moulding

Cores

• Cores serve to produce internal surfaces in castings. In some cases they have to be supported by chaplets for more stable positioning:

Cores• Cores are made of foundry sand with addition of

some resin for strength by means of core boxes

METAL FORMING PROCESS

• Plastic Deformation Processes 

– Operations that induce shape changes on the workpiece by plastic deformation under forces applied by various tools and dies.

 • Bulk Deformation Processes

– These processes involve large amount of plastic deformation. The cross-section of workpiece changes without volume change. The ratio cross-section area/volume is small.

– For most operations, hot or warm working conditions are preferred although some operations are carried out at room temperature.

Classification of Bulk Deformation Processes

• Forging:– The work piece is compressed between two opposing

dies so that the die shapes are imparted to the work.– There are many different kinds of forging processes

available, however they can be grouped into three main classes:• Drawn out: length increases, cross-section decreases • Upset: Length decreases, cross-section increases • Squeezed in closed compression dies: produces

multidirectional flow

Forging operation

Hand forging

Hand forging

Shaft forging

Forging products

Forging products

Rolling

• Compressive deformation process in which the thickness of a plate is reduced by squeezing it through two rotating cylindrical rolls.

Rolling operation

Rolling mill

Rolling of rod

Rolling of sheet metal

Hot rolling operation

Extrusion

• The work material is forced to flow through a die opening taking its shape

Extrusion operation

Tube extrusion

Extrusion products

Drawing

• The diameter of a wire or bar is reduced by pulling it through a die opening (bar drawing) or a series of die openings (wire drawing)

• Drawing is a forming process in which the metal is stretched over a form. In deep drawing the depth of the part being made is more than half its diameter. • Deep drawing is used for making automotive fuel tanks, kitchen sinks, 2 piece aluminum cans etc.

METAL CUTTING PROCESS

• Lathes: – In a turning or facing operation on a lathe, the work piece rotates to

provide the cutting motion, and the feed is by motion of the cutting tool.

– Lathes are used for the production of all kinds of components which are symmetrical about their axis of rotation.

• Drilling Machines: – The cutting action results from the rotary movement of the cutting tool

or work piece, with a feed motion of the work piece or tool, in the direction of the rotating axis.

– Drilling machines are used for drilling, boring, counter-sinking, reaming and tapping operations.

• Milling Machines: – In the case of milling, both the tool and the work piece can move

horizontal or vertical direction. – Milling machines are used to produce flat surfaces, sink, and slot.

Basic Operation of a Lathe

• A lathe is a machine tool which turns cylindrical material, touches a cutting tool to it, and cuts the material.

Photo graph ic vi ew of Lat he

CNC Lathe

Three Important Elements 1.Cutting speed

It expresses with the number of rotations (rpm) of the chuck of a lathe. 2. Depth of cut

The cutting depth of the tool affects to the processing speed and the roughness of surface. 3. Feed rate

  The sending speed of the tool also affects to the processing speed and the roughness of surface.

LATHE OPERATIONS • Turning

 – Turning is a machining process to produce parts round in shape by a single point

tool on lathes. – The tool is fed either linearly in the direction parallel or perpendicular to the axis

of rotation of the work piece, or along a specified path to produce complex rotational shapes.

– The primary motion of cutting in turning is the rotation of the work piece, and the secondary motion of cutting is the feed motion.

• Operations in Turning

– Turning is not a single process but class of many and different operations performed on a lathe.

• Turning of cylindrical surfaces – The lathe can be used to reduce the diameter of a part to a desired dimension.

The resulting machined surface is cylindrical.

Lathe operations-Turning

Turning of flat surfaces• A lathe can be used to create a smooth, flat face very accurately

perpendicular to the axis of a cylindrical part. Tool is fed radially or axially to create a flat machined surface.

• Facing is the process of removing metal from the end of a work piece to produce a flat surface.

Lathe operations- facing

Lathe operations-Contour profiling/Taper turning

• Cutting tool has a simple shape, but the feed motion is complex; cutting tool is fed along a contour thus creating a contoured shape on the work piece. For profiling, special lathes or devices are required.

Lathe operations- Knurling• This is not a machining operation at all, because it

does not involve material removal. Instead, it is a metal forming operation used to produce a regular crosshatched pattern in the work surface.

Lathe operations-Threading• Threads are cut using lathes by advancing the cutting tool at a feed exactly

equal to the thread pitch. The single-point cutting tool cuts in a helical band, which is actually a thread.

• Another possibility is to cut threads by means of a thread die (external threads), or a tap (internal threads). These operations are generally performed manually for small thread diameters.

Lathe operations- Forming• Cutting tool has a shape that is imparted to the work piece by

plunging the tool into the work piece. • In form turning, cutting tool is complex and expensive but feed

is linear and does not require special machine tools or devices.

Miscellaneous operations

• Some other operations, which do not use the single-point cutting tool, can be performed on a lathe, making turning one of the most versatile machining processes.

Drilling

• It is a cutting process that uses a drill bit to cut or enlarge a hole in solid materials.

• The drill bit is a multipoint, end cutting tool. It cuts by applying pressure and rotation to the work piece, which forms chips at the cutting edge.

Hand drilling machine

• Hand drill is commonly used for drilling of small holes

Drill press

Drill press is preferable when the location and orientation of the hole must be controlled accurately

Radial drilling machine

• This is the largest drill press designed to drill up to 100-mm diameter holes in large work parts. It has a radial arm along which the drilling head can be moved and clamped.

Drilling method

Drilling Operations

• Core drilling is used to increase the diameter of an existing hole;• Step drilling is used to drill a stepped (multi-diameter) hole in a solid

material;• Counter boring provides a stepped hole again but with flat and

perpendicular relative to hole axis face. The hole is used to seat internal hexagonal bolt heads;

• Countersinking is similar to counter boring, except that the step is conical for flat head screws:

• Reaming provides a better tolerance and surface finish to an initially drilled hole. Reaming slightly increases the hole diameter. The tool is called reamer;

• Center drilling is used to drill a starting hole to precisely define the location for subsequent drilling. The tool is called center drill. A center drill has a thick shaft and very short flutes. It is therefore very stiff and will not walk as the hole is getting started;

Various Drilling Operations

Drilling tools and reaming operation

Milling

• The conventional milling machines provide a primary rotating motion for the cutter held in the spindle, and a linear feed motion for the work piece, which is fastened onto the worktable.

• Milling machines for machining of complex shapes usually provide both a rotating primary motion and a curvilinear feed motion for the cutter in the spindle with a stationary work piece.

Column-and-knee milling machines• The column-and-knee milling machines are the

basic machine tool for milling. The name comes from the fact that this machine has two principal components, a column that supports the spindle, and a knee that supports the work table.

• There are two different types of column-and-knee milling machines according to position of the spindle axis:

-horizontal-vertical

Types of milling – Down (climb) milling, when the cutter rotation is

in the same direction as the motion of the work piece being fed, and

– Up (conventional) milling, in which the work piece is moving towards the cutter, opposing the cutter direction of rotation:

Two basic types of column-and-knee milling machines, (left) horizontal and (right) vertical

Photographic view of Horizontal milling machine

Photographic view of Vertical milling machine

MILLING OF FLAT SURFACES

• Peripheral Milling- In peripheral milling, also called plain milling, the axis of

the cutter is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter.

- The primary motion is the rotation of the cutter. The feed is imparted to the work piece.

Face milling

• In face milling, cutter is perpendicular to the machined surface. The cutter axis is vertical, but in the newer CNC machines it often is horizontal.

• In face milling, machining is performed by teeth on both the end and periphery of the face-milling cutter.

MILLING OF COMPLEX SURFACES

Form milling• In form milling, the cutting edges of the peripheral cutter

(called form cutter) have a special profile that is imparted to the work piece.

• Cutters with various profiles are available to cut different two-dimensional surfaces.

Profile milling

• In profile milling, the conventional end mill is used to cut the outside or inside periphery of a flat part.

• The end mill works with its peripheral teeth and is fed along a curvilinear path equidistant from the surface profile.

Surface contouring

• The end mill, which is used in surface contouring has a hemispherical end and is called ball-end mill.

• The ball-end mill is fed back and forth across the work piece along a curvilinear path at close intervals to produce complex three-dimensional surfaces.

• Similar to profile milling, surface contouring require relatively simple cutting tool but advanced, usually computer-controlled feed control system.

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