Singh Abhishek Ravinder141080119052Semister-4rd

Mechanical Dept.

MANUFACTURING PROCESS IIGROUP NO:. 9

SHEET METAL FORMINGAND OPERATIONS

1.0 Introduction

Sheet metal is simply metal formed into thin and flat pieces. Sheet metal is essentially metal pressed into sheets. These sheets are used at

various places. These sheets can be bent, cut and molded into any shape for use anywhere.

Sheet metal is generally produced in sheets by reducing the thickness of work piece by compressive forces applied through a set of rolls.

Sheets

Sheet Metal Forming How to differentiate a sheet

and a plate ?

O If thickness is less than 6 mm (1/ 4 inches) then it is regarded as sheet.

O If thickness is greater than 6 mm (1/ 4 inches) then it is regarded as plate.

Applications of sheet metalsO Aircraft Bodies

O Automobiles bodies

O Utensils used for domestic purposes

O Beverage cans

Cutting OperationsShearing by two sharp cutting edges.Plastic deformation penetration

fracture

Shearing, Blanking and Punching

Shearing - Cutting on sheet-metal with straight edges.

Blanking - Cutting sheet-metal with a closed contour.

Punching - Making holes on sheet-metal.

Sheet-metal Cuttingc = atc = clearancea = allowancet = thickness

Blanking:Blanking punch dia. = Db-

2cBlanking die dia. = Db

PunchHole punch dia. = Db

Hole die dia. = Db+ 2c

Sheet-metal Cutting

Small clearance

Large clearance

Cutting force = StLS = Shear strength of sheet-metalt = Sheet-metal thicknessL = Length of cutting edgeor, Cutting force = 0.7TtLT = Ultimate tensile strength of sheet-metal

Sheet-metal Cutting Operations

Cut-off

Parting

Slotting Perforating Notching / Seminotching

Sheet-metal Cutting Operations

Fine blanking -close tolerances and smooth edges in one step.Trimming - Cutting operation to remove excess metal

Shaving - Shearing with very small clearance to obtain accurate dimensions., secondary or finishing operation.

Bending

V- bending Edge - bending

Bending AnalysisBA = 2 A( R + Kbat ) / 360where BA = bending allowance, A = bend angle, R = bend

radius, t = stock thickness, Kba = stretch factor.For R< 2t, Kba= 0.33 ; for R 2t, Kba= 0.5.

Spring back,

where A’ = include angle of sheet-metal part A’b = include angle of bending tool w = width of sheet-metal

Bending force D = die opening dimension Kbf = 1.33 V-bending

Kbf = 0.33 edge bending

b

b

AAASB

DTwtK

F bf2

Bending AnalysisSpring back

Die-openingdimension

Bending Operations

Straight flanging Stretch flanging Shrink flanging

Hemming Seaming Curling

Bending Operations

Channel bending U-bending air-bending

Offset-bending Corrugating Tube forming

Drawingc = ClearanceDb = blank

diameterDp = Punch

diameterRd = die corner

radiusRp = Punch

corner radius

F = drawing forceFh = holding

force

Deep Drawing

Initial step bending of edge straightening of side wall

Thinning and drawing final cup shape

Drawing Defects

a) Wrinkling in flange - small holding forceb) Wrinkling in the wall - insufficient holding

force, wrinkling initially occurring on the flange.c) Tearing - high stress, sharp die radiusd) Earing - anisotropy of the materiale) Surface scratches - Die or punch not having a

smooth surface, insufficient lubrication

Other Sheet-metal Operations

Ironing - squeezing and drawing in conjunction

Corning & Embossing - to produce surface details

Lancing - combination of cutting and forming

Other Sheet-metal Operations

Rubber forming processes:

Guerin process - low cost, small volume, pressure up 10 MPa.

Hydroforming - Higher pressure, up to 100 MPa.

Dies

Components of a punch and die for blanking operation

DIE CUTTINGO It is combination of following operationsOPerforating.OParting or shearing a sheet into two.ONotching or removing pieces in edges.OLancing or leaving a tab with removing any material

SLITTINGOShearing operation –using circular bladesOThese blades follow straight line or circular

path or curved path – depending upon requirement.

NIBBLINGONibbler (tool) move straight up and moves

down rapidly.OSheet metal is fed in gap between two cutting tools and produces overlapping holesOSuitable small runs, several intrcate shapes can be produced.

PIERCINGO It is a shearing operation.O Creates open hole in sheet metal by

separating the interior section.O Removed metal is discarded as scrap

PART

slug

BLANKING:

O It is also a shearing operation.O It enlarges earlier pierced hole.O Removed metal is desired one.

PARTPART

SLUG

OVery smooth and square edges can be obtained by fine blanking.

DiesProgressive

dies and final part

Press

Press are driven mechanically or hydraulically.

Knuckle jointcrankshaft

eccentric

Stretch Forming

Stretching and forming with a die at the same time.

Roll FormingSimilar to the the rolling process but working on sheet-metal or tubes.

Spinning

Conventionalspinning

Shear spinning - thinning and bending occur at the same time.

Spinning

Tube spinning - similar to shear spinning but working on a tube.

High Energy Forming

Explosive formingElectrohydraulic formingElectromagnetic forming

Tube Bending

Stretch bending

Drawing bending

Compression bending

R/D 3.0 with mandrelR/D 1.5 without

mandrel

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