Drop forging report

2. DROP FORGING
Drop forging is a mass production technique
which hammers the metal between two dies. Half of
the die is attached to the hammer (upper section)
and half to the anvil (lower section). The hot metal is
placed in the lower half of the die and struck one
on more time with the upper die. This forces the
metal to flow in all directions, filling the die cavity.
Excess metal squeezed out between the die faces is
called flash or flashing. After the forging is
completed the flash is cut off in another press with a
trimming die.

4. A metal shaping process, the metal to be
formed is first heated then shaped by forcing it into
the contours of a die, this force can be in excess of
2000 tons. The drop forging process can be
performed with the material at various
temperatures;
Hot Forging
During hot forging the metals are heated to
above their recrystallization temperature. The main
benefit of this hot forging is that work hardening is
prevented due to the recrystallization of the metal
as it begins to cool.

5. Cold Forging
Cold Forging is generally performed with metal at
room temperature below the recrystallization temperature.
Cold forging typically work hardens the metal
TWO TYPES OF DROP FORGING
OPEN DIE
Drop forging requires the operator to position the work
piece while it is impacted by the ram. The die attached to the
ram is usually flat or of a simple contour, most of the shaping is
achieved by the operator physically positioning the work piece
before each stroke of the ram. There are also special dies which
can be used to cut the metal, form holes or notches.

6. CLOSED DIE (Impression die)
Drop forging comprises of a die on the anvil which
resembles a mould, the ram which falls and strikes the top of
the metal billet can also be equipped with a die. The
heated metal billet is placed on the lower die while the ram
drives down forcing the metal to fill the contours of the die
blocks.

7. Process details
Closed-die forging
A heated blank is placed between 2 halves of a
die

8. A single compressive stroke squeezes the blank into
the die to form the part. In hammer or drop forging
this happens by dropping the top of the mould from
a height. An alternative is to squeeze the moulds
together using hydraulic pressure.

9. Once the die halves have separated, the
part can be ejected immediately using an
ejector pin.

10. The waste material, flash, is removed later.

11. Advantages
1.  Parts of sizes up to 25 tons can be
produced with closed die forging
 
2. Closed die forging can produce near net
shapes that will require only a small amount
of finishing
 
3. Economic (profitable) for large runs of
product
 

12. 4. Forging provides superior mechanical
properties over castings due to the
internal grain structure formation in
forged parts
5. Makes strong products.
6. Many metals are forged cold, but iron
and its alloys are always forged hot.

13. Disadvantages
1. Not very economical for short runs due to the high
cost of die production
 
2. The business set up cost of drop forging is very
high, not only are the machines and furnaces costly
but special building provisions must be in place to
cope with the powerful vibrations caused by drop
forging. A special foundation must be laid to deal
with this environment
 
3. Drop forging presents a dangerous working
environment

14. Materials and shapes
1. Any metal can be forged, provided the
blank is hot enough (( 60% of the melting
temperature).
2. Typical possible sizes for closed dies range
from 10g to 10kg, depending on complexity.
3. The part is left with good surface and
mechanical properties, although cold-forging
can perform even better.

15. 4. Complex parts can be formed using a
series of forging dies with increasing levels of
detail.
5. A draft (taper) angle has to be
incorporated to allow easy removal of the
part.
6. Any waste material squeezed between the
die halves, called flash, is readily recycled.

16. Economics
Production rate is limited by the insertion and
removal of the blank, so some form of
automation is often used.
As a result, machines can cost £100,000+, but
can produce many parts a minute (if small).
As both the machines and the dedicated dies
are costly, production runs in excess of 50,000
are often needed to produce small parts
economically.
Large parts can be produced economically at
smaller batch sizes, because there is less
competition.

17. APPLICATION
Typical Products
Spanners
pedal cranks
gear blanks
valve bodies
hand tools
crankshafts
coins

18. MATERIALS USED
The materials that are used most commonly in drop
forging are: aluminium, copper, nickel, mild steel,
stainless steel, and magnesium.
Best Material: Mild Steel
Worst Material: Magnesium