Sheet Forming Processes

Sheet Forming Processes:

The manufacturing process in which shape change is achieved through plastic deformation.

Keep in mind that the increase in temperature will results in decrease in strength, increase ductility and decrease the rate of strain hardening.

• Sheet Material   →   which have large surface area to volume ratio.
• Bulk Material   →   which have lesser surface area to volume ratio.

There are three basic operation in sheet metal working:

1. Cutting or Shearing
2. Bending 
3. Deep Drawing

1. Shearing (Cutting) Operations:

It is the mechanical Cutting of materials without the formation of chips or the use of burning or melting.

There are different types of cutting operations:

A. Simple Shearing:

When metal sheets are to be cut along a straight line between two cutting edges.

B. Slitting:

It us the lengthwise shearing operation used to cut coils of sheet metal into several rolls of narrower width.

C. Blanking:

It involves cutting of sheet along a closed outline in single step to separate the peice from the surrounding stock.

D. Piercing:

It is similar to blanking but it produces a hole. The separated peice is called slug or scrap and the remaining part is stock.

Variation in Piercing are:

I. Slotting:

It is a piercing operation that cuts put an elongated or rectangular hole.

II. Perforating:

It involves the piercing of a pattern holes on sheet metal.

III. Notching:

It involves the cutting of a portion of metal from the side of sheet.

IV. Semi-Notching:

It involves the cutting of a portion of metal from side and as well as interior part of metal.

V. Lancing:

Piercing operation that forms either a line cut, slit or hole.

2. Bending Operations:

It is the plastic deformation of metals about a linear axis with no change in the surface area.

• If multiple bends are to be made with a single die, the process is called Forming.

A. V-Bending:

Bending operation at angle with V-dies. Sheet metal is bent between a V-shaped punch and die.

B. Edge-Bending:

Bending operation in which metal is bent by wiping dies.

C. Flanging:

Bending operation in which the edge of a sheet metal part is bent at a 90 degree to form a rin or flange.

D. Curling:

It is also called bending which forms the edges of the part into a roll or curl.

E. Hemming:

It involves the bending of the edge of the sheet over itself.

F. Seaming:

It is the bending operation that can be used to join ends of sheet metal to form mechanical interlock.

G. Roll Bending:

It is a continuous form of three-point bending where plates, sheets, beams, pipes and even rolled shapes and extrusions are bent to be desired curvature using forming rolls.

3. Drawing Operations:

Operations in which plastic flow occurs over a curved axis.

• The clearence between pick and die is about 10% greater than the stock thickness.
• The punch applies downward force to accomplish deformation and a downward holding force is applied by the blank-holder.

A. Deep Drawing:

When the depth of the product is greater than the diameter, the process is called Deep Drawing.

B. Shallow Drawing:

When the depth of the product is less than the diameter, the process is called Deep Drawing.

C. Spinning:

A cold forming process in which rotating disk of sheet metal is progressively shaped over a mandrel to produce rotationally symmetrical shapes.

D. Embossing:

It is a press working process I which raised letter or other designs are impressed in sheet material.

Reference:

• University Notes 
• Book Fundamental of Modern Manufacturing 6th Edition by Mikell P. Groover
• Videos from youtube and Google 
• Images from google images