Deep Drowing

DEEP DRAWING FOR SHEET METAL

Deep Drawing:Deep Drawing is a sheet metal forming operation used to make cup- box-shaped ,or other complex curved, hollow shaped parts.i.e Kitchen sink , cylinders , containers of all shape and size. etc

DEFINATION

If the depth of the item created is equal to or greater than its radius, then the metal forming process called deep drawing.

Many parts made of sheet metal are cylindrical or box -shaped :for example, pots and pans,containetrs for food and kitchen sinks ,an automotive fuel tanks. Such parts are usually made by a process in which a punch forces on a flat sheet metal blanks into a die cavity. The process is generally called deep drawing.

INTRODUCTION

Examples

Examples

Types of Deep Drawing:

i) Convential. Ii) Unconvential

Convential: The formability limitations of conventional deep drawing are a barrier for some industrial uses. Radial drawing stress and tangential compressive stress are a common concern that can result in wrinkling, fracturing or cracking in some applications.

Unconvential:Numerous unconventional deep drawing techniques have helped to increase the industrial uses of deep drawing. These processes include hydro -forming, hydro-mechanical deep drawing, hydraulic deep drawing, and the Marform process.

Metals used in Deep Drawing:

  Different metals are used in deep drawing in which some metals are these

1:Alloy

2:Aluminum

3:Brass

4:Cold rolled steel

5:Copper

6:Iron

The Deep Drawing Process

In the basic method ,a round sheet metal blank is placed over a circular die opening and is held in place with a blankholder,or hold-down ring. The punch travels downward and forces the blank into the die cavity, forming a cup.

Process

Video:

Example:

Production of utensils for house hold use

video

Deep Drawability (LDR) : The limiting drawing ratio(LDR), defined as the maximum ratio of blank diameter D0 to punch diameter Dp that can be drawn without failure.

LDR= Do/Dp

Maximum value of LDR=2.7Its value depends on the radius of punch , radius of die, hold down pressure, clearance and lubrication.

Normal Anisotropy:The ratio of width strain to thickness strain

R=strainw/straint

is known as normal anisotropy of sheet metal.The value of R is different for different materials.Average value of ‘R’ can be calculated as

R=R0+2R45+R90/4

Deep Drawing Practice:1-Clearance and Radii:

Generally, clearance are 7-14% greater then the original thickness of the sheet . As the clearance decreases, ironing increases. The corner radii of the punch and of the die are also important. if they are too small, they can cause fracture at the corners; if they are too large, the cup wall may wrinkle

Draw Beads

To control the flow of the blank into the die cavity.Beads restrict the flow of the sheet metal by bending and

unbending in during drawing.

Draw bead diameters may rang from 13 mm to 20 mm (0.5 in to 0.75 in).

Ironing: If the thickness of the sheet as it enters the die cavity is more then the clearance between thepunch and the die, it has be reduced by a deformation called ironing.

Redrawing: Containers are shells that are too difficult to draw in one operation generally undergo redrawing. Because of volume constancy, the cup becomes longer as it is redrawn to smaller diameter. In reverse redrawing the cup is placed upside down in the die and thus bending in the direction opposite to its original configuration.

Drawing without Blankholder: Deep drawing carried out successfully without a blank holder with only a single action press, provided that the sheet metal is sufficiently thick to prevent wrinkling. A typical range is D0 – Dp < 5T Where T is the sheet thickness.

Lubrication

In deep drawing ,lubrication lowers forces, increases drawability,and reduces defects in the parts. In general lubrication of the punch should be held because friction between the punch and the cup improves draw-ability.

Commonly used lubricants are mineral oils, soap solutions, and wax.

Advantages of Deep Drawing

Deep drawing is especially beneficial when producing high volumes, since unit cost decreases considerably as unit count increases:

Once the tooling and dice have been created, the process can continue with very little downtime or upkeep. Tool construction costs are lower in comparison to similar manufacturing processes, such as progressive die stamping, even in smaller volumes; in these situations deep drawing may also prove the most cost-effective manufacturing solution.

When considering the functionality of the end product, deep drawing poses still more advantages. Specifically, the technique is ideal for products that require

significant strength and minimal weight  .

Deep drawing may be a viable production solution for any manufacturing process that requires one or more of the following. 

Rapid cycle

times: large quantities of products are easily manufactured through deep drawing

Complex axis-symmetric geometries: deep drawing delivers exceptional detailing and accuracy

Deep drawing a Viable production

 Difference between Deep drawing and bar drawing

Deep drawing is a sheet metal forming process used to fabricate cup-shaped parts; bar drawing is a bulk deformation process used to reduce the diameter of a cylindrical work part. The basic drawing

process for a bar

Difference between deep drawing and stretch forming

Deep drawing is a metal forming process in which sheet metal is stretched into the desired part shape. A tool pushes downward on the sheet metal, forcing it into a die cavity in the shape of the desired part.

Stretch forming is a metal forming process in which a piece of sheet metal is stretched and bent simultaneously over a die in order to form large contoured parts. Stretch forming is performed on a stretch press, in which a piece of sheet metal is securely gripped along its edges by gripping jaws .

Difference between deep drawing and stretch forming

Stretch-forming

Industrial use:Industrial uses of deep drawing processes include automotive body and structural parts, aircraft components, utensils and white goods .

Commercial application

Commercial applications of this metal shaping process often involve complex geometries with straight sides and radii.

APPLICATIONS

Haseen Habib (PVT)Head Office and Factory                   123/3 Quaid-e-Azam Industrial Estate,Haseen Habib Road, Kot Lakhpat,Lahore/Pakistan.Tel: (042) 3512 4400Fax :(042) 3512 3197

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