This slideshow tells you about punching and blanking process,the two widely used manufacturing process in sheet metal industry.

1. PUNCHING AND
BLANKING PROCESS
Presented By: Presented To:
Nilabrata Bera Dr. Biswanath Dolui
Anupam Halder

2. Introduction:
 Punching and blanking processes are sheet metal forming
processes.
 In these two processes a finite volume of metal from a
sheet is removed by using die and punch.
 The shape and size of the portion removed depends on
the geometry of die and punch.
 Also the operation cost and time depends on die and
punch design.

3. Application:
 Automobile industries.
 Aerospace industries.
 Kitchen appliances.
 Mass production of sheet metal components.

4. CuttingTool & Job Material:
 The cutting tool(punch and die) are made of hardened
steel or tungsten carbide.
 The sheet metal to be machined is generally made of
aluminium, brass, copper, stainless steels.
 In some cases plastic is also used.

5. Difference:
 In the punching process the final product is the metal
sheet from which metal is removed.
 In blanking process the final product is the removed
portion from the sheet.

6. Punching Press:
 It is a type of machine press used to cut the material.
 Can be very simple and manually controlled or very
complex and CNC controlled.

7. DriveType of Punch Presses:
 Flywheel Drive
 Mechanical Punch Press
 Hydraulic Punch Press
 Servo Direct Turret Punch Press

8. Different Zones of Blanked Part:
 Rollover Zone (Zr)
 Shear Zone (Zs)
 Fracture Zone (Zf)
 Burr Zone (Zb)
 Depth Of Crack Portion (Dcp)
 Secondary Shear

10. Process:
 The job is held by job holders to prevent distortion.
 A clearance is provided between the punch and die.
 Force is given on the job by the punching tool.
 A finite portion of metal is removed from the sheet.

11. Die diameter(d1)=d2+2c
d2-punch diameter, c-clearance

12. Deformation ofWorkpiece:
 The job bends and is pulled down by the punch
movement.
 The grains elongate at A,B & D.
 When the elongation reaches a limiting value , rupture
occurs.

13. Working Force:
 The maximum force required to create a complete
rupture is, Fmax=σf Co L (σf -true rupture stress, Co -
optimum clearance. L-length of cut).
 The maximum force required can be reduced by avoiding
the simultaneous failure of the total area.
 This is done by providing an angle to the punch edge.
 But the total energy requirement remains same.

14. Effective Clearance:
 The amount of clearance given is very important.
 As the velocity of propagation of fracture lines is very
high, they may miss each other without optimum
clearance.
 In optimum clearance, a clean edge is obtained.
 In case of too little or too large clearance, secondary
deformation takes place.

15. Stripping Force
 Two actions take place in the punching process-punching
and stripping.
 A stripping force develops due to spring back of the
punched material that holds the punch.
 This force is generally expressed as a percentage of the
force required to punch the hole.
 The value of stripping force is generally given by the
equation,
SF = 0.02 L * t( L-length of cut , t-thickness of material).

16. ProcessVariants:
Depending on the shape of the metal removed or process,
there are some special types of Blanking processes-
 Fine Blanking
 Notching
 Lancing
 Slitting
 Nibbling
 Trimming

17. Fine Blanking Process:
 A special type of blanking process.
 Fracture zone does not form while shearing.
 Very tight tolerance is achieved by this process.
 Aluminium , brass, copper ,stainless steels are the metals
that can be fine blanked.

18. Notching:
 In notching, material is removed from the side of a sheet
material.

19. Lancing:
 Lancing process makes partway through the metal
without producing any scrap.

20. Slitting:
 It is an operation to cut a coiled sheet metal lengthwise
to produce narrower strips.

21. Nibbling:
 In nibbling operation, complicated shapes are cut out from
a sheet metal by producing overlapping notches.
 Without using any special tools, a simple, round or
triangular punch is reciprocated at a fixed location.
 The sheet metal is guided to obtain the desired shape of
cut.

22. Trimming:
 Trimming process refers to the removal of excess material
in a flange or flash.

23. Advantages:
 Punching and blanking are quick processes.
 The slug produced may be reused or recycled(depending
on material).
 It is often the cheapest and most cost effective method
for medium to high volume of production.
 It can create multiple shaped holes or same shaped holes
very fast.

24. Disadvantages:
 Equipment and tooling costs are high.
 Often needs secondary finishing operations to smooth
out burrs along the bottom edge.
 Fine blanking process is a slow process.

25. Conclusion:
 Punching and blanking process is very cost effective
process.
 Though the initial equipments cost may be high but it is
very useful for mass production.
 Very closer dimensional tolerance can be achieved by fine
blanking process.

26. References:
 Manufacturing Science(Amitabh Ghosh,Asok Kumar
Mallik)
 www.wikipedia.org
 www.nptel.ac.in
 www.slideshare.net
 Degarmo’s Manufacturing Science

27. ThankYou