mi 231 manufacturing technology – i 1-15

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Manufacturing Technology – IMI 231

Autumn 2011-2012

Instructor – Dr. Akshay Dvivedi

Relative Weightage of Marks

Class Work Sessional (CWS): 15%Practical Sessional (PRS): 15%Mid Term Examination (MTE): 30%End Term Examination (ETE): 40%

Manufacturing Technology – IMI 231

Objective: To impart knowledge about the process principles, equipment, and applications of different forming processes, machining operations, and grinding processes.

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Contents Contact Hours

1 Introduction: Classification of different manufacturing processes, application areas and limitations, selection of a manufacturing process.

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2 Press Working of Sheet Metal: Types of presses, drives and feed mechanisms; Operations: Shearing, bending, spinning, embossing, blanking, coining and deep drawing; Die materials, stock layout, compound and progressive dies and punches, construction details of die set, auxiliary equipment, safety devices.

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3 Machine Tools and Operations: Classification of machining processes and machine tools, cutting tool materials, different types of cutting tools, nomenclature of single point and multi point cutting tools, concept of cutting speed, feed and depth ofcut, use of coolants, constructional details including accessories and attachment, operations, setting and tooling for capstan and turret lathes, drilling, boring and broaching machines, milling operations.

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COURSE CONTENT

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Contents Contact Hours

4 Grinding: Operations and applications of surface, cylindrical and centreless grinding processes, dressing, truing and balancing of grinding wheels, grading and selection of grinding wheels.

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Total 28

COURSE CONTENT

Suggested Books

1998Rao, P.N., “Manufacturing Technology”, (Vol. 2), Tata McGraw-Hill

5.

1990Lindberg, R.A., “Processes and Materials of Manufacture”, Prentice-Hall of India

4.

2002Groover, M.P., “Fundamentals of Modern Manufacturing”, John Wiley & Sons

3.

2000Kalpakjian, S., and Schmid, S.R., “Manufacturing Engineering and Technology”, Pearson Education

2.

1997DeGarmo, E. P., Black, J.T., and Kohser, R.A., “Materials and Processes in Manufacturing”, Prentice-Hall of India

1.

Year of Pub.

Name of Authors /Books /PublisherS. No.

Different Components…Different Aspects

SmallSimple

Big Complex

23 feet,6 tonnes ,99.72% iron,No rust since 5th

century AD

Iron pillar

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Manufacturing – Need and concept

• Manufacturing - Value addition processes by which raw materials (low utility and value due to inadequate material properties and poor or irregular size, shape and finish) are converted into valued products (high utility due to definite dimensions and finish

imparting functional ability.

Value addition by manufacturing.


Production Engineering covers two domains: – Production or Manufacturing Processes– Production Management

• Manufacturing Processes - science and technology of manufacturing products effectively, efficiently, economically and environment-friendly through: – Application of any existing manufacturing process and

system– Proper selection of input materials, tools, machines and

environments.– Improvement of the existing materials and processes– Development of new materials, systems, processes and

techniques


Production Engineering covers two domains:

– Production or Manufacturing Processes

– Production Management

• Production Management - planning, coordination and control of the entire manufacturing in most profitable way with maximum satisfaction to the customers by best utilization of theman, machine, materials and money. Goal in manufacturing requires fulfillment of one or more of the following objectives:– Reduction of manufacturing time

– Increase of productivity

– Reduction of manufacturing cost

– Increase in profit or profit rate



Material flow is of three main types:

• Through flow, corresponding to mass-conserving processes (change in material properties without change in geometry)

• Diverging flow, corresponding to mass-reducing processes

• Converging flow, corresponding to assembly or joining processes

Manufacturing – Need and conceptA manufacturing process normally consists of a series of basic

processes, which constitute the structure of the material flow.

• Basic processes can be divided into three typical phases:– Phase 1 (material into a suitable state/geometry like heating, melting,

sawing etc.)

– Phase 2 (desired geometry and/or change in properties)

– Phase 3 (component into the specified end state (solidification, cooling, deburring etc.)

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Engineering Manufacturing Processes

(a) Shaping or forming Manufacturing a solid product of definite size and shape from a given material taken in three possible states: – Solid state – e.g., forging rolling, extrusion, drawing etc.

– Liquid or semi-liquid state – e.g., casting, injection molding etc.

– Powder form – e.g., powder metallurgical process.

(b) Joining process – Welding, brazing, soldering etc.

(c) Removal process– Machining (Traditional or Non-traditional), Grinding etc.


(d) Regenerative manufacturing • Production of solid products in layer by layer from raw

materials in different form:– Liquid – e.g., stereo lithography– Powder – e.g., selective sintering– Sheet – e.g., LOM (laminated object manufacturing)– Wire – e.g., FDM. (Fused Deposition Modeling)

Engineering Manufacturing Processes Engineering Manufacturing Processes

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Factors affecting the selection of manufacturing processes

• Cost (material, manufacturing, operating and replacement cost)

• Material (specified by design)

• Quantity (determines economics of manufacturing process)

• Machine or equipment availability (Machines and operators)

• Quality (Surface finish, Accuracy (geometrical, dimensional)

• Geometry (Cylindrical, conical, threads – Lathe)

(Plane surface, slots – shaping, planning, milling)

(Complex Shapes – Casting, Forging)

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Secondary Metal Shaping Selecting materials for manufacturing

• Mechanical properties of materials

– Strength, toughness, ductility, hardness, elasticity, fatigues,

creep, …

• Physical properties of materials

– density, specific heat, thermal expansion and conductivity,

melting point, and electrical and magnetic properties, ……

• Chemical properties, environmental resistance and wear

– corrosion, toxicity, flammability, ……

• Strength : ability to bear load before fracture

• Toughness: resistance to both elastic and plastic deformation

• Ductility: extent of permanent or plastic deformation that a material undergoes before fracture (% elongation, % reduction in area

• Hardness: resistance to plastic deformation which includes indentation, scratching, or marking

• Elasticity: ability to restore to original shape and size after removal of external deforming loads

• Fatigue : permanent deformation and/or failure of a component when subjected to fluctuating (both in magnitude and direction) loads

• Creep : permanent deformation and/or failure of a component when subjected to high stresses at high temperature

• Stiffness: resistance to elastic deformation

• Fracture : splitting of a component into atleast two halves

Material-Based Selection of Manufacturing Processes

XX - Widely Used

X - Seldom Used

-- - Not Used .

--XX--XXComposites

--XXXXXPolymers

----X--XXCeramics

XXXXXXXXXXMetals

ModifyingJoiningRemovingDeformingForming

Mat

eria

ls

Application Range of Manufacturing Processes According to Melting Temperature of the Material and Batch Size

[G. Chryssolouris, 1991]

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• Deformation processes have been designed to exploit the

plasticity of engineering materials

• Plasticity is the ability of a material to flow as a solid without

deterioration of properties

• Deformation processes require a large amount of force

• Processes include bulk flow, simple shearing, or compound

bending

Classification of Deformation Processes

• Bulk deforming processes can be classified as primary or secondary processes

– Primary processes reduce a cast material into slabs, plates, and billets

– Secondary processes reduce shapes into finished or semi finished products

• Bulk deformation processes are those processes where the thickness or cross sections are reduced

• Sheet-forming operations involve the deformation of materials whose thickness and cross section remain relatively constant

Classification of States of Stress

Bulk Deformation Processes

• Rolling• Forging• Extrusion• Wire, rod, and tube drawing• Piercing• Squeezing processes

Sheet-forming Operations

• Sheet - thickness < 5 mm • Sheet metal processes involve plane stress loadings and lower

forces than bulk forming• Almost all sheet metal forming is considered to be secondary

processing

Stress Induced Operations

Shearing Shearing, Blanking, Piercing, Trimming, Shaving, Notching, Nibbling

Tension Stretch-Forming

Compression Ironing, Coining, Sizing, Hobbing

Tension and Compression

Drawing, Spinning, Bending, Embossing, Forming

Classification of Presses

• Primary tool for sheet metal working is some form of press and successful manufacture depends on using right kind of equipment

– Capacity required

– Type of power (manual, mechanical, or hydraulic) or drive

– Number of slides or drives

– Type of frame

– Speed of operation

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Press drive mechanisms

Classification of Presses – Drive Mechanism

• Very light work - manually operated presses (foot operated or kick presses)

• Heavier work – mechanical drives

• Fast motion and positive control of displacement

• Limited flexibility (length of stroke is set by design of drive)

• Force varies with position

• Preferred for operations like cutting, up to 10 cm drawing (maximum pressure near bottom of stroke)

• Capacity – 9000 metric tons


• Mechanical drives types:– Crank-driven

• Simple

• Piercing, blanking, drawing

• Double crank (multiple action dies)

– Eccentric or cam drives• Used for smaller ram stroke

• Dwell at bottom of stroke

• Deep drawing

– Knuckle-joint drives• High mechanical advantage alongwith fast action

• Coining


• Mechanical drives types:– Toggle mechnism

• Drawing– Screw-type drives

• Mechanical action resembling drop hammer


• Hydraulic presses

– Motion as a result of piston movement

– Stroke can be programmed (2.5 m)

– Accurate controlled on forces and pressure

– Availability of full pressure throughout the stroke

– Speeds can be programmed to either vary or remain constant

– Slower than mechanical presses in general (exception – 600

strokes per minute for high speed blanking)


• Hydraulic presses– Reproducibility of position will have greater variation than a

mechanical press– Capacity - exceeding 50,000 metric tons– Preferred for operations

• requiring a steady pressure throughout a substantial stroke (deep drawing)

• requiring wide variation in stroke length• requiring high or widely variable forces.

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Classification of Presses – Frame

• Considerations – capacity, accessibility and stiffness– limitations on size and type of work that can be

accommodated– Work loading and unloading– Press setup time e.g., time required for changing dies

• Arch-frame– Screw-drives for coining– Seldom used

• Gap-frame (C shaped)– Versatile– Good accesability from three directions– Permit large workpieces– 1 metric ton to 300 metric tons

Classification of Presses – Frame

• Inclinable press– Tilted – Ejection can be assited by gravity or compressed air jet

• Open-back presses– Opening in back– Easy ejection of products/scraps

• Turret press– Multiple holes/slots with varying shaps/size– Upper and lower turret (muliple punches and dies)

• Horn press– Cylindrical shaft (horn) in place of bed– Curved workpieces– Seaming, punching, riveting

Inclinable gap-frame press

Horn press

Classification of Presses – Frame• Straight-sided press

– Accesibility from front and rear (from sides as well)

A 200-ton straight-sided press.

Sheet Metalworking

1. Cutting Operations

2. Bending Operations

3. Drawing

4. Other Sheet Metal Forming Operations

Sheet and Plate Metal Products

• Sheet and plate metal parts for consumer and industrial products such as – Automobiles and trucks

– Airplanes

– Railway cars and locomotives

– Farm and construction equipment

– Small and large appliances

– Office furniture

– Computers and office equipment

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Advantages of Sheet Metal Parts

• High strength

• Good dimensional accuracy

• Good surface finish

• Relatively low cost

• Economical mass production for large quantities

Sheet Metalworking Terminology

• Punch-and-die - tooling to perform cutting, bending, and drawing

• Stamping press - machine tool that performs most sheet metal operations

• Stampings - sheet metal products

Basic Types of Sheet Metal Processes

1. Cutting

– Shearing (simple shearing) to separate large sheets

– Blanking to cut part perimeters out of sheet metal

– Punching/ Piercing to make holes in sheet metal

– Slitting

2. Bending

– Straining sheet around a straight axis

3. Drawing

– Forming of sheet into convex or concave shapes

Shearing, Blanking, and Punching

Principal operations in pressworking that cut sheet metal:

• Shearing

• Blanking

• Punching

• Piercing

Shearing

• Shearing is a process for cutting sheet metal to size out of a larger stock such as roll stock.

• Shears are used as the preliminary step in preparing stock for stamping processes, or smaller blanks for CNC presses

• The shearing process produces a shear edge burr, which can be minimized to less than 10% of the material thickness. The burr is a function of clearance between the punch and the die, and the sharpness of the punch and the die.

Shearing

• Fracture and tearing begin at the weakest point and proceed progressively or intermittently to the next-weakest location

– Results in a rough and ragged edge

• Punch and die must have proper alignment and clearance

• Sheared edges can be produced that require no further finishing

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Shearing of sheet metal between two cutting edges:

(1) just before the punch contacts work;

(2) punch begins to push into work, causing plastic deformation;

Sheet Metal Cutting - Shearing

Shearing of sheet metal between two cutting edges:

(3) punch compresses and penetrates into work causing a smooth cut surface;

(4) fracture is initiated at the opposing cutting edges which separates the sheet.

Sheet Metal Cutting - Shearing

Fineblanked surface

Conventionally sheared surfaceSmooth shearing a rod by putting it into compression during shearing

Slitting - Power shear for 6.5 mm steel

Shearing (Press Operations)Shearing

Sheet metal cutting operation along a straight line between two cutting edges

• Typically used to cut large sheets

Shearing operation:

(a) side view of the shearing operation;

(b) front view of power shears equipped with inclined upper cutting blade.

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Shearing

• Shearing (simple/square)

– Both cutting blades are straight

• Curved blades to produce different shapes

– Blanking

– Punching

– Piercing

– Notching

– Trimming

Blanking and Punching

Blanking - sheet metal cutting to separate piece (called a blank) from surrounding stock

Punching - similar to blanking except cut piece is scrap, called a slug

Blanking Punching

Blanking and Punching

Blanking - sheet metal cutting to separate piece (called a blank) from surrounding stock

Punching - similar to blanking except cut piece is scrap, called a slug

Punching

• Punching is a metal fabricating process that removes a scrap

slug from the metal workpiece each time a punch enters the

punching die. This process leaves a hole in the metal workpiece

Characteristics:

• Ability to produce holes in both strip and sheet metal during

medium or high production processes.

• The ability to produce holes of varying shapes - quickly

Punching

• The punching process forces a steel punch, made of hardened steel, into and through a workpiece.

• The punch diameter determines the size of the hole created in the workpiece

• Punching is often the cheapest method for creating holes in sheet metal in medium to high production.

Punching

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Punching and Piercing

• A slug (the material punched out) is produced in punchingoperations but not in piercing work

• Piercing is “forming a hole in sheet metal with a pointed punch with no metal fallout (slug).”

• In this case, a significant burr or deformed sharp edge is created on the bottom side of the material being pierced.

PIERCE

PUNCHES

Piercing & blanking -Tools and Dies

• Basic components of a piercing and blanking die set are: punch, die, and stripper plate

• Punches are normally made from low-distortion or air-hardenable tool steel so that they can be hardened after machining


• Theoretically, punch should fit in die with a uniform clearance approaches zero (practically- 5-7% of stock thickness)

• Uniform clearance should be maintained around the entire periphery

• Theoretically, punch should not enter die, but should stop as its base aligns with top surface of die (practically- punch enters slightly in die)


• Punch tilted slightly to reduce cutting force (shear angle)

• Shear angle – reduces force – increases stroke length


• Subpress dies (modular tooling) – assembled and combined on bed of press to pierce or blank large parts


•Dies– single piece

– component sections (that can be assembled)

•simplifies production•simplifies replacement

•flexibility of design changes

•standard die components

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Parts requiring multiple cutting type operation

• Progressive die sets- two or more sets of punches and dies mounted in line (one behind another, all facing in the same direction)

• Transfer dies move individual parts from operation to operation within a single press

• Compound dies combine processes sequentially during a single stroke of the ram


Progressive die sets• First operation

– strip stock is fed in first die, where a hole is pierced and ram descends

• Second Operation– ram retracts and strip

advances, the pilot on blanking punch aligns with pierced hole

– further descent of punch blanks the completed washer-pieces

– At same time, first punch pierces the hole for next washer

Progressive piercing and blanking die for making a square washer


Progressive die sets

Eleven station progressive die stages


Progressive die sets• Used for multiple combinations of piercing, blanking,

forming, drawing etc. • Quick and accurate position of work material• Simple construction• Economical to maintain and repair• Require final cut-off operation


Transfer die sets• Part handling must operate in harmony with press motions

to move, orient and position the pieces as they travel through the die

Piercing & blanking -Tools and DiesCompound die sets• Piercing and blanking (or other combinations) occur

sequentially during a single stroke of ram

Part is blanked and subsequently pierced in the same strokeThe blanking punch contains the die for piercing.

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Compound die sets

• More complex• More breakage• More expensive• Precise alignment

Nibbling

• Contour is progressively cut by producing a series of overlapping notches (removing the material in small increments)

• Simple tools for complex shapes

• Nibbling is used when the contour is long and a separate punch is impractical and uneconomical

• Edge smoothness – determined by shape of tooling and degree of overlap in successive cuts

Lancing

• Metal cutting operation in which the metal is sliced or slit to free up metal without separating it from the original sheet.

• Does not create a slug

• Save material and eliminate the need for scrap removal

• Done in progressive dies

Trimming

• Removal or Trimming of the Flash

Shaving

• Finishing operation

• Removal of the burrs left on product during the blanking or punching/piercing operation

• Greater dimensional accuracy

• Close tolerance work

Notching

• Cutting a specified small portion of material towards the edge of the material stock

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Cutoff

• Separate a stamping or other product from a strip or stock

• Produces the periphery counter to the workpiece

Dinking

• Used to blank shapes from low strength materials (rubber, fiber, cloth etc.)

(Hammer or mechanical press acts on shank)

Design for Piercing and Blanking

• Design rules

– Diameters of pierced holes should not be less than the

thickness of the metal (minimum 0.3 mm)

– Minimum distance between holes or the edge of the stock

should be at least equal to the metal thickness

– The width of any projection or slot should be at least 1

times the metal thickness (never less than 2.5 mm)

– Keep tolerances as large as possible

Bending

• Bending is the plastic deformation of metals about a linear axis with little or no change in the surface area

• Forming- multiple bends are made with a single die

• Spring-back is the “unbending” that occurs after a metal has been deformed

Bending

Bend Allowance is length of neutral axis in bend

Lb = α (R + kT)

Where,

α is bend angle (rad),

T is sheet thickness,

R is bend radius,

k is constant (from (0.33 for R<2T) to 0.5 (for R>2T))

Ideal case k = 0.5

Bending

(a) bending (b) rolling (c) Bending 90o

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Bending BendingMinimum Bend Radius - the ratio at which a crack appears on

outer surface of bend

Expressed in terms of thickness (2T, 3T, 4T etc.)

R = T(50/(r-1))

Where,

R is bend radius, T is sheet thickness, r is tensile reduction of area of sheet metal

R/T Ratio versus % Area Reduction

50% tensile reduction of area can bebent over itself

BendingBending Force

• Simple bending of a rectangular beam

• Bending force is function of :– strength of material

– length of bend (L)

– thickness of sheet (T)

– size of die opening (W)

• Maximum bending force is

P = kYLT2 / W

Where, T is sheet thickness, R is bend radius,

k is 0.3 – 1.3, Y is yield stress

Angle Bending (Bar Folder and Press Brake)

• Bar folders make angle bends up to 150 degrees under 1.5 mm sheet metal

• Press brakes make bends in heavier sheets or more complex bends in thin material

Press Brake• Heavier sheet and/or complex bends

• Mechanical/Hydraulic with narrow/long bed and short strokes

• Optional operations - Seaming, embossing, punching etc.

• 7 m long sheets

• Die material– hardwood (low strength materials)

– Carbon steels, gray-iron

Press Brake

Roll Bead Formed

(a) Bead forming with a single die (b) Bead forming with two dies, in a press brake

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Bending

Springback

Ri/ Rf = 4(RiY/ET)3 - 3(RiY/ET) + 1

Where, Y is yield stress, E is elastic modulus

• Spring back increases with decrease of E and increase of R/T and Y

• Springback

Q. A 5 mm sheet is bent to a radius of 10 mm. Calculate the radius of part after it is bent

(Yield stress = 205 MPa, E = 190 Gpa)

Ri / Rf = 4(RiY/ET)3 - 3(RiY/ET) + 1 (overbend or springback allowance)

RiY / Et = (10 x 205 * 106) / (190 x 109 x 5) = 0.00216

Ri / Rf = 4 (0.00216)3 – 3 (0.00216) +1

= .993

BendingSpringback

• Remove the bent piece at stage (b) – positive spring back• Upon unloading at stage (d) – negative spring back (inwardly)

because it is being unbent from stage c• The amount of this inward (negative) spring back can be

greater than the amount of positive spring back

Bending

Springback

Bending

Springback

Design for Bending

• Several factors are important in specifying a bending operation– Determine the smallest bend radius (R/T = (50/(r-1))) that can be

formed without cracking the metal

– Metal ductility (reduction in area in uniaxial tensile test)

– Thickness of material

Relationship between the minimum bend radius (relative to thickness) and the

ductility

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Considerations for Bending

• If the punch radius is large and the bend angle is shallow,

large amounts of spring back are often encountered

• The sharper the bend, the more likely the surfaces will be

stressed beyond the yield point

• Parts with multiple bends should be designed with most of

them at same bend radius (less setup time and tooling cost)

• Bends should be made with the bend axis perpendicular to

the rolling direction (fracture in hard material)


• The minimum inner radius should be at least 1 material thickness

• Minimum flange width should be at least 4 times the stock

thickness plus the bending radius (damage to tooling or operator)

• Tolerance should not be less than 0.8mm


• Forming Near Holes – When a bend is made too close to a hole, the hole may become deformed (teardrop) – For a hole < 1" in diameter the minimum distance "D" = 2T + R

– For a slot or hole > 1" diameter then the minimum distance "D" = 2.5T + R

A. Teardrop B. hole < 1” C. hole > 1”

Air-Bend, Bottoming, and Coining Dies

• Bottoming dies contact and compress the full area within the tooling– Angle of the bend is set by

the geometry of the tooling

• Air bend dies produce the desired geometry by simple three-point bending

• If bottoming dies go beyond the full-contact position, the operation is similar to coining

Air-bend (left) and bottoming (right) press brake dies

Roll Forming

• Roll forming is a process by which a metal strip is progressively bent as it passes through a series of forming rolls

• Only bending takes place during this process, and all bends are parallel to one another

• A wide variety of shapes can be produced, but changeover, setup, and adjustment may take several hours

Roll Forming

• Progressive bending of metal strips as it passes through series of forming rolls (80m.min)

• Any material that can be bent can be rolled

Eight-roll sequence for the roll forming of a box channel

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Roll Bending

• Roll bending is a continuous form of three-point bending

– Plates, sheets, beams, pipes

– Lower rolls – driven

– Upper roll – controls degree of curvatureForming Rolls

Draw Bending, Compression Bending, and Press Bending

(a) Draw bending, in which the form block rotates

(b) moving tool compresses the workpiece against a stationary form

(c) press bending, where the press ram moves the bending form.

Tube Bending

• Wet Sand

• Flexible mandrels

• Pressure bulging

• Key parameters: outer diameter of the tube, wall thickness, and radius of the bend

Tube Bending

Production of fittings for plumbing(expanding tubular blanks)

Seaming and Flanging

• Seaming is a bending operation that can be used to join the ends of sheet metal in some form of mechanical interlock

• Common products include cans, pails, drums, and containers

• Flanges can be rolled on sheet metal in a similar manner as seams

Various types of seams used on sheet metal.

Straightening

• Opposite of bending• Done before subsequent forming to ensure the use of flat or

straight material • Various methods to straighten material

– Roll straightening (Roller levering)– Stretcher leveling- material is mechanically gripped and stretch

until it reaches the desired flatness

Method of straightening rod or sheet by passing it through a set of straightening rolls

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Drawing and Stretching Processes

• Drawing refers to the family of operations where plastic flow occurs over a curved axis and the flat sheet is formed into a three-dimensional part

Deep Drawing and Shallow Drawing

• Deep drawing is typically used to form solid-bottom cylindrical or rectangular containers from sheet metal

• Shallow drawing - depth is less than diameter

Deep Drawing and Shallow Drawing

• Key variables:– Blank and punch diameter

– Punch and die radius

– Clearance

– Thickness of the blank

– Lubrication

– Hold-down pressure

Limitations of Deep Drawing

• Typical limits to drawing operations

– Wrinkling (movement of blank into die cavity induce compressive stresses in flange)

– Tearing (walls elongates and tend to thin)

– Earing (Edges of cups may become wavy)


• Shallow Drawing – little change in circumference and small area is confined by blankholder

• Deep Drawing – more change in circumference

• More wrinkle and tear -Thin material

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Deep Drawing

• Deep Drawability (LDR)– LDR = Do/Dp– Where, Do – max. blank diameter, Dp – is punch diameter

• Ability of a sheet metal for sucessful drawing operation is defined by normal anisotropy (R)R = Width strain / Thickness strain Cold rolled sheets have anisotropyin planer directionRave = (R0+ 2R45+ R90)/4Where angles are relative torolling direction

Deep Drawing

• Earing is caused by planer anisotropy of sheet (ΔR)

• ΔR = (R0 -2R45+R90)/2

• at ΔR = 0, no ears are formed


• Different techniques can be used to overcome these limitations

– Simple shapes – Multiple operations

– Complex shapes - Draw beads

– Vertical projections and matching grooves in the die and blankholder

• Trimming may be used to reach final dimensions


• Forward redraw - material undergoes reverse bending as it flows into the die

• Reverse redrawing – starting cup is placed over a tubular die and punch acts to turn it inside out]

Draw beads

• Control flow of blank in die cavity

Ironing

• Process that thins the walls of a drawn cylinder by passing it between a punch and a die

• Die and Punch Set Used is Similar to that of Drawing Operation Except that the Clearance Between the Die and Punch is Smaller than that Used in the Drawing Operation.

• The Material Gets Compressed Between Punch and Die which Reduces the Thickness and Increases the Height.

• The Wall Thicknesses can be Reduced to as Much as 50% in a Single Ironing Operation.

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Embossing• Press working process in which raised lettering or other

designs are impressed in sheet material

• Drawing and bending of the material

• Die set consists of a die and punch with the desired contours, so that when the punch and die meet, the clearance between them is same as that of the sheet thickness

• Providing dimples on sheets to increase their rigidity

• Decorative sheet work used for panels

Spinning

• Produces rotationally symmetrical shapes

– Spheres, hemispheres, cylinders, bells, and parabolas

• Sheet metal is rotated and shaped over a male form and gradually moving force is applied (blank takes shape of form)

• Setup – Centre lathe– Head stock – hard wood form block (desired shape)

– Tail stock – Blank ( freely rotating, hard wood or metal)

Spinning

• After Proper Clamping, the Blank is Rotated to its Operating Speed.

• Spinning Speed Depends on the Blank Material, Thickness and Complexity of the Desired Cup.

• Then the Hard Wood or Roller Type Metallic Tool is Pressed and Moved Gradually on the Blank so that it Conforms to the Shape of the Form Block.

• Spinning is Comparable to Drawing for Making Cylindrical Parts.

Spinning

• Spinnability –

– as the ability of a metal to undergo shear spinning deformation without exceeding its tensile strength and tearing

– Related to tensile reduction of area

Spinning Types

1. Conventional spinning– Conical and curvilinear shapes

– Normally at room temperature

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Spinning Types

2. Shear Spinning

• Part diameter is maintained where as thickness is reduced

• Considerable forces

• Considerable heat

• Requires cooling

• Tooling – tool steels

• No wastage of material

• Balancing required

Spinning Types

3. Tube Spinning

• Thickness is reduced by spinning them on cylindrical mandrel

using rollers

• Reduction depends on tensile reduction of area of the material

• Both external or internal

• Both forward or backward

COINING • Closed–die forging

operation (the flow of the material occurs only at the top layers and not in the entire volume)

• Coining die consists of the punch and die which are engraved with the necessary details required on both sides of the final object.

• The blank is compressed by the die with a very high pressure (5 to 6 times strength of material) is applied due to which very fine details are obtained on the surface.

Tool and Die Materials

• High strength, impact toughness, wear resistance at room and elevated temperatures

Tool and Die Materials

• Shearing

– Cold D2, A2, A9, S2, S5, S7

– Hot H11, H12, H13

• Press Working Zn alloys, 4140 steel, CI, Comp., A2, D2, O1

• Deep Drawing W1, O1, Ci, A2, D2

• Coining W1, O1, A2, D2, D3, D4, H11, H12, H13

Safety devices• Barrier guards

– Prevent operators exposure to nip points and pinch points

– Fixed, adjustable or self-adjusting

– Mechanical, electric, hydraulic, and optical interlocks are provided untill barrier guards are in place

1. Spring-type interlockshuts off power to machinewhen guard door is opened2. Guard can only beremoved by removing thePlugSource : Triodyne , Inc.

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Safety devices

• Dead-man Control: power is automatically shut off in the event of operator passes out or dies – e.g. belt strap in elevated cranes

• Presence setting devices

Safety devices

• Maintenance – Zero mechanical state

• Locking out

• Personal protective equipment ( goggles, face shields, ear plugs, helmets, gloves, aprons etc.)

Machining Machining• Machining

– A subtractive process used to get desired shape, size, and finish by removing surplus material in the form of chipsby a cutting tool and by providing suitable relative motion between the workpiece and cutting tool

– Process of finishing by which jobs are produced to the desired dimensions and surface finish by gradually removing the excess material from the preformed blank in the form of chips with the help of cutting tool (s) moved past the work surface (s).

• Machining requirements Using SINGLE-Point

Cutting ToolsUsing MULTI-Point

Cutting Tools

Using ABRASIVES as Cutting Tools

Turning Step Turning Taper Turning Form Turning Contour Turing

Facing Necking Parting-Off Boring

Counter-Boring Counter-Sinking

Shaping Planing

Milling Drilling Reaming Knurling Sawing

Grinding Honing Lapping Polishing Buffing

Machining Processes

Unconventional Machining Processes

AJM, USM, WJM

ECM, ECG

CHM

IBM, PAM, EDM, LBM, PAM

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Machine tool

• A machine tool is a non-portable power operated and reasonably valued device or system of devices in which energy is expended to produce jobs of desired size, shape and surface finish by removing excess material from the preformed blanks in the form of chips with the help of cutting tools moved past the work surface (s)

• Physical functions of a Machine Tool in machining are: – firmly holding the blank and the tool – transmit motions to the tool and the blank– provide power to the tool-work pair for the machining

action– control of the machining parameters, i.e., speed, feed and

depth of cut

Basic Machine Tools Centre lathes

– Cylindrical shapes

– Manual lathes or CNC

Basic Machine Tools

Centre lathes

External

Internal

Basic Machine Tools Shaping machine• Ram: it holds and imparts cutting motion to the tool through

reciprocation

• Bed: it holds and imparts feed motions to the job (blank)

• Housing with base: the basic structure and also accommodate the

drive mechanisms

Basic Machine Tools Shaping machine• Power drive with speed and feed change mechanisms

• Shaping machines are generally used for producing flat surfaces,grooving, splitting etc.

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Basic Machine Tools

Planing machine• In planing the job reciprocates for cutting motion and the tool

moves slowly for the feed motions unlike in shaping machine.

• Planing machines are usually very large in size and used for

large jobs and heavy duty work.

Basic Machine Tools

Drilling machine

• Drilling (originating or enlarging cylindrical holes)

• Boring, counter boring, counter sinking etc.

• Cutting internal threads in parts like nuts using suitable attachment

Basic Machine Tools

Drilling machine

• Column with base: it is the basic structure to hold the other parts

• Drilling head: this box type structure accommodates the power drive and the speed and feed gear boxes

• Spindle: holds the drill and transmits rotation and axial translation to the tool for providing cutting motion and feed motion – both to the drillD

• Pillar drill, column drill, radial drill, micro-drill etc.

Basic Machine ToolsMilling machine• Flat surfaces• Slotting• Slitting• Grooving• Parting• Forming

Classification of Machine Tools

1. Direction of major axis– horizontal center lathe, horizontal boring machine etc. – vertical – vertical lathe, vertical axis milling machine etc. – inclined – special

2. Purpose of use– general purpose – e.g. lathes, milling, drilling machines etc. – single purpose – e.g. facing lathe, roll turning lathe etc. – special purpose – for mass production

3. Number of spindles– single spindle – center lathes, milling machines etc. – multi-spindle – gang drilling machines etc.


4. Degree of automation

– Manual – e.g. lathes, drilling machines etc.

– Semi-automatic – e.g. turret lathe

– Automatic – e.g., CNC Drill, CNC Mill, CNC lathe etc.

5. Type of automation

– fixed automation – e.g., single spindle and multispindlelathes

– flexible automation – e.g., Machining Centers6. Precision

– Ordinary

– High precision

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7. Size – Heavy duty – e.g., heavy duty lathes (e.g. ≥ 55 kW), boring

mills, etc.– Medium duty – e.g., lathes (e.g. – 3.7 ~ 11 kW), column

drilling machines etc. – Small duty – e.g., table top lathes, drilling machines,

milling machines. – Micro duty – e.g., micro-drilling machine etc.

6. Configuration– Stand alone type – most of the conventional machine tools. – Machining system – e.g., machining center, FMS etc.

Cutting Tool

• Removes excess material through direct mechanical contact

• Tool moves along the workpiece at a certain velocity (cutting speed – V) and a depth of cut (to) to produce a chip just ahead of tool by shearing the material continuously along the shear plane

Tool material Selection depends on:

• Work material (hardness, chemical and metallurgical state)

• Part features (geometry, accuracy, finish, surface-integrity)

• Machine tool characteristics (rigidity, horsepower, speed, feed , precision)

• Support system (Operator, sensors, controls, method of chip removal, lubrication, maintenance)

Cutting Tool

Tool Selection (material, geometry, cutting conditions)

Cutting Tool

• Tool Material Characteristics

– Hardness

– Toughness

– Wear Resistance

– Chemical Inertness

– Resistance to bulk deformation

– Thermal Properties

– High Stiffness

– Geometry

– Finish

Cutting Tool

Hardness of cutting materials

Hardness—resistance to deforming and flattening

Cutting Tool

Wear resistance—resistance to abrasion and erosion

Toughness—resistance to breakage and chipping

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Cutting Tool Cutting Tool

Cast-cobalt alloys (1915)


• Tool steels• HSS• Coated HSS• Cast Cobalt Alloys• Carbides / Sintered Carbides• Coated Carbides• Ceramics• Cermets• Diamonds• Polycrystalline CBN’s

– and many more…………..

Cutting ToolTool steels• Carbon and low-/medium-alloy steels• Steel is considered to be carbon steel:

– when no minimum content is specified or required for Cr, Co, molybdenum, Ni, Ti, W, V or zirconium etc.

– when the specified minimum for copper does not exceed 0.40 percent;

– when the maximum content specified is less than Mn - 1.65, Si - 0.60, Copper - 0.60.

– steel which is not stainless steel• 0.9 to 1.3% carbon• With increase in carbon content, steel become harder and

stronger

Cutting ToolTool steels• With increase in carbon content, steel become lesser ductile

and melting point decrease

• Hardness loss at 200 0C

• Mo and Cr increases hardenability

• Mo and W improves wear resistance

• Applications

– Drills, Taps, Dies etc.

– Low speeds

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Cutting ToolHSS• Good wear resistance, hardenability and hot hardness• Good toughness and resistance to fracture• Good cutting at 400 0C• Easy fabrication• Types

– Molybdenum (M series)• 10% Mo with Cr, V, W, Cr and Co• High abrasion resistance than t series• Less Distortion than T series• Cheaper than T series

– Tungsten (T series)• 12-18% W, Cr, V and Co (18-4-1 W-Cr-V)

• Used for complex tool geometries

Cutting ToolTiN coated HSS• Film thickness 0.00254 - 0.00508 mm• 10-20% higher cutting speeds than HSS• Gear cutters, drills, bandsaw, circular saw blades, form tools,

inserts etc.• Reduced tool wear• High hardness• PVD

Cutting ToolCast Cobalt Alloys• Cobalt rich, chromium-tungsten-carbon cast alloys • Stellite tools (Deloro Stellite Company)• Non-magnetic and corrosion-resistant cobalt alloy• W or Mo and a small amount of carbon• Retain hardness to much greater temperatures• 25 % higher cutting speeds than HSS• Cast to shape• Used only for single point tools or saw blades

Cutting ToolCarbide or Sintered Carbides• Types:

– Tungsten carbide (WC bonded together in a cobalt matrix)• 1-5 µm WC particles are combined with cobalt in a mixer, then presses and

sintered into the desired insert shapes.• Cemented carbides \ Sintered Carbides• With increase of Co – toughness increases but there is decrease in strength,

hardness and wear resistance• Machining steels, CI, nonferrous and nonmetals

– Titanium Carbide (TiC in Ni-Mo alloy matrix)• Higher wear resistance than WC• Lesser toughness than WC• Machining hard materials like steels, CI • Higher speeds than WC• Finishing and semifinishing ferrous alloys• Auto industry using Ni-Mo binder

Cutting ToolInserts• Individual cutting tools with several cutting points• Sq inserts (8 cutting edges), triangular insert (6 cutting edges)

Cutting Tool

Inserts are clamped on tool shank with various locking mechanisms

• (a) Clamping

• (b) Wing lock pins

• (c) Thread-less lock pins - secured with side

• (d) Brazed on a tool shank

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Cutting Tool

Chip Breaker

• Continuous chips are undesirable as they are a potential safety hazard

• Cutting at low speed may lead to welding of chips to tool face

• Ideal chip – Shape of letter “C” or number “9” and fits within 25 mm square block

• Procedure used for breaking chips intermittently is with use of chip breaker

Cutting Tool

Chip Breaker(a) tightly curled chip(b) chip hits workpiece and breaks(c) continuous chip moving away from workpiece(d) chip hits tool shank and breaks off

Cutting Tool

Chip Breaker

• Controlling chip flow

• Eliminating long chips

• Reducing vibration and heat

Cutting Tool

Chip Breaker

• Chip breaking in softer materials like Al include machining at small increments and then pausing.

• In shaping, milling or other such intermittent operations chip breakers are not required

Cutting Tool

• American National Standards Institute (ANSI) – C-1 to C-8

• ISO Standards – P, M and K

Classification of Tungsten Carbides

Cutting Tool

ISO Classification of Carbide Cutting ToolsAccording to Use

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Cutting Tool

Coated Carbide tools• Coating increase tool life by 200-300 times

• Coating increase 50-100% in speed of the same tool life

• 80-90 % of carbide tools are coated

• Bulk tool material can be tough, shock resistant carbide that can withstand

high temperature plastic deformation and resist breakage

• Thin chemically stable, hard refractory coating of TiC, TiN, TiCN or

Al2O3, Diamond, TiAlN, CrC, ZrN etc.

• Fine grained coatings

• Free form binders and porosity

• Low coeff. of friction for coating – non adherence of chips on rake face

Cutting Tool

Coated Carbide tools• Single or multiple• Multiple coating provide stronger metallurgical bond between

coating and substrate• For multiple coating:

– Innermost layer should bondwith substrate

– Outermost layer should resistwear

– Intermediate layer shouldbond well and be compatiblewith both layers


Ceramics (White or cold-presses ceramics)• 1950• Pure Aluminium oxide, Al2O3, or SiC• Pressed into insert shapes

under high pressure• TiC and ZrO may be

added to improve toughness and resistance to thermalshock

Cutting Tool

Ceramics• Particulates or whiskers• 2 to 3 times cutting speed than WC• High hardness and chemical inertness• Hard and brittle – require rigid tool holders and machine tools• Less tendency to adhere to metals during machining – good SF • Used for high speed cutting/finishing of super-alloys and high

strength steels• Not suitable for Al, Ti as they react with alumina based

ceramics

Cutting Tool

Cermets (Ceramics + Metal)

• Black or hot-pressed ceramics

• Mix of 70% aluminium oxide and 30% TiC

• Intermediate performance between ceramics and carbides

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Cutting Tool

Polycrystalline CBN• High hardness (Knoop 4700 at 20 oC 4000 at 1000 oC)• Low chemical reactivity• 0.5-1 mm layer of PCBN is bonded to a carbide substrate by

sintering under pressure.• Carbide provides toughness – CBN provides high wear

resistance and cutting edge strength• Used for automotive industry• Used for aerospace materials• Higher cost than ceramics tools or cemented carbides but tool

life is 5-7 times that of a ceramic tool

Difficult-to-machine materials

Cutting Tool

Polycrystalline CBN

PCBN Tips

Solid PCBN

Cutting Tool

Diamond

• High Wear resistance, low tool-chip friction, sharp cutting edges

• Used for fine surface finish and dimensional accuracy

• Brittle - Light and uninterrupted finishing cuts

• High speed machining and fine feeds

• Single-crystal diamond tool – machining optical mirrors

• Polishing is not required after machining

• Polycrystalline diamond tools (compacts or industrial diamonds) – small synthetic crystals, fused by high pressure and temperature to a thickness of .5-1 mm and bonded to a carbide substrate

Tool Geometry