The document provides information on various sheet metal processes including sheet metal basics, classifications, cutting, bending, deep drawing, ironing, spinning, hydroforming, and explosive forming. It discusses the mechanics and considerations for processes like cutting, bending, deep drawing, and defines related terms like clearance, drawing ratio, reduction, etc. The document is intended to educate readers on fundamental sheet metal engineering concepts and manufacturing techniques.

1. Sheet Metal Processes
Prof. K.N.Wakchaure
Dept. of Mechanical Engineering
SRES COLLEGE OF ENGINEERING,
KOPARGAON

7. Sheet Metal Basics
• Sheet metal thickness:-0.15 to 6mm
• Metal Plates:- >6mm
• Foils: <0.15mm

8. • Sheet and plate have different applications. Plate is
generally used for larger structural parts like boilers,
turbines, bridges, and ships.
• Sheet metal is used in the manufacture of cars, trains,
aircraft, farm equipment, office equipment, furniture, house
appliances, computers, machine components, and beverage
cans to name a few.
• Sheet metal products typically have high strength, good
surface, and accurate tolerances.

9. Sheet Metal Classification
• Cutting: Cutting is the use of shearing forces to remove material
from a work piece. Technically not a metal forming process, but of
extreme industrial importance.
• Bending: Bending is the forming of a sheet metal work about an
axis.
• Deep Drawing: Deep drawing is the forming of a cup or box with a
flat base and straight walls, from a sheet metal blank.
• Other Processes: Other sheet metal working processes such as
ironing, spinning, rubber forming, and high energy rate forming are
also discussed in latter sections.

10. Sheet Metal Cutting
• Sheet metal cutting is a major classification of many
kinds of press working operations.
• Press working, a term referencing sheet metal
operations in general, involves the working of a
sheet between two die.
• Cutting operations involve the separation of
material of the sheet in certain areas.
• This separation is caused by shearing forces acting
on the metal through the edges of the punch and
die.

12. • Industrial sheet metal working operations such as
this will usually incline the punch so as to reduce
the maximum force needed by distributing the
required force over the cutting stroke.
• The angle the punch may be inclined varies from 4
to 15 degrees, however the higher the angle, the
greater the magnitude of the horizontal force
component acting to displace the work.
• For that reason angles are usually under 9 degrees.

13. Cutoff And Parting Of Sheet

14. Blanking
• Blanking is the cutting of a sheet metal part along a closed
contour in one step. The piece cut out is called a blank, and
may be further processed. Many blanks are often
continuously cut out of a sheet or strip.
• Blanking will waste a certain amount of material. When
designing a sheet metal blanking process, the geometry of
the blanks should be nestled as efficiently as possible to
minimize material waste.
• A distinction should be made between blanking and
punching, since essentially they are the same process. In
punching the piece cut out is waste.
• In blanking, the piece cut out is the work and is kept.

16. Nibbling
• Punches for the cutting of holes and profiles may come
in many different shapes and sizes.
• A machine called a nibbler uses a small straight punch to
create the same geometric removal of sheet metal as
that of a larger more complicated punch.
• It does this by rapidly punching many overlapping holes
to make the larger cut profile. Nibbling is useful in
producing intricate cuts with simple machinery.
• Nibbling may take longer than a punch specifically
designed for a certain cut, however it may be an efficient
alternative for small production runs.

17. Perforating
• Sometimes it is desirable to punch many holes in a piece of sheet
metal, often in a certain pattern.
• These holes may be round or some other shape. Perforating sheet
metal will allow for the passage of light or fluid material through
the material.
• It can often serve in ventilation and filtration of fluid substances.
Perforated sheet is also used in structure and machinery
construction to reduce weight and for cosmetic appearance.
• Special equipment is employed that punches many holes at once,
and at a high rate.
• In industrial practice the size of these holes is usually from (1-
75mm).
• The upper rate at which some special perforating machines can
punch holes is 100,000 to 300,000 per minute

19. Shaving
• Edge surfaces of cut sheet metal are not typically
smooth and straight. Even in properly cut metal the
fracture zone will be angled and rough.
• In sheet metal cutting, the lower the clearance value
the higher the edge's quality.
• Shaving is a secondary process that can be used to
improve edges of cuts that have already been made.
• Shaving uses very little clearance to perform a
straight, smooth, accurate cut to only the end of the
edge.

21. Mechanics Of Cutting Sheet Metal
• Mechanics of cutting sheet metal should be
understood when designing a sheet metal
manufacturing process. The work piece in such an
operation is secured to the lower die, while the
motion of the upper die, (called a punch), enacts the
cutting.

24. Clearance
• In manufacturing industry there is a range of optimum
values for specific processes, clearances may span from
1% to 30% of sheet thickness.
• Generally, typical values span from 3% to 8% of sheet
thickness.
• A large factor is the type of work material and its temper.
Aluminum alloy sheet might have an optimum clearance
value of 4%, a brass sheet 6%, and a hard steel sheet
7.5%.
• If the hole size is small relative to total sheet thickness,
extra clearance could be needed.

34. Sheet Metal Bending

46. Mechanics Of Sheet Metal Bending

48. Methods Of Eliminating Springback

49. Stretch Forming
• Sheet metal is clamped at edges and stretched over
a die or form block
• Dies made of zinc alloys, steels, plastics, wood
• Little or no lubrication
• Low-volume, versatile, and economic production
Products: aircraft wing skin
panels, automobile door panels,
window frames

55. Deep Drawing
• Deep drawing is a process that is used
extensively in the forming of sheet metal into
cup or box like structures.
• Pots and pans for cooking, containers, sinks,
automobile parts, such as panels and gas
tanks, are among a few of the items
manufactured by deep drawing.

58. • Clearance in deep drawing manufacture is
greater than sheet thickness, usually clearance
values are 107% to 115% of sheet thickness.

60. Drawing Ratio
• Measurement of the amount of drawing performed on a blank can
be quantified. This can be done with the drawing ratio.
• The higher the drawing ratio, the more extreme the amount of
drawing.
• Due to the geometry, forces, metal flow, and material properties of
the work, there is a limit to the amount of drawing that can be
performed on a blank in a single operation.
• Drawing ratio is roughly calculated as
DR = Db/Dp.
• Db is the diameter of the blank and Dp is the diameter of the punch.
• The limit to the drawing ration for an operation is usually 2 or
under.

61. Reduction
• Another way to express drawing ratio is the reduction
(r).
• Reduction is measured using the same variables as
drawing ratio.
• Reduction can be calculated by r = (Db - Dp)/(Db).
• Db and Dp being blank and punch diameters
respectively.
• Reduction ratio should be .5 or under. Often expressed
as the percent reduction r = (Db - Dp)/(Db) X 100%.
• In this case the reduction should be 50% or under.

62. • If required percent reduction is over 50%, the part
must be formed in multiple operations. Redrawing is
the subsequent deep drawing of a work that has
already undergone a deep drawing process.

65. Ironing
• Ironing can be incorporated into a deep drawing process or can be
performed separately.
• A punch and die pushes the part through a clearance that will act
to reduce the entire wall thickness to a certain value.
• While reducing the entire wall thickness, ironing will cause the part
to lengthen.
• The percentage reduction in thickness for an ironing operation is
usually 40% to 60%.
• Percent reduction can be measured
(ti - tf)/ti X 100%.
• With ti being initial thickness, and tf being final thickness. Many
products undergo two or more ironing operations. Beverage cans
are a common product of ironing operations.

68. Spinning

73. Hydroforming
• Hydroforming is an effective sheet metal forming process.
• Hydroforming can typically obtain deeper draws than
conventional deep drawing operations. Hydroforming
uses a rigid punch to push a sheet metal work piece into a
rubber membrane.
• Behind the rubber membrane is a chamber of pressurized
fluid. When the work is pressed into the chamber the
rubber membrane surrounds it completely and the
pressure of the fluid forces the sheet metal to form on the
punch.
• Fluid pressure can be controlled during the operation, and
can be as high as 15,000 lbs/in2, (100MPa).

74. Explosive Forming

77. Design Consideration

82. Numerical

83. Numerical

84. Numerical

85. Numerical

86. Numerical

87. Thank you