Dr. B.R. AMBEDKAR NATIONAL INSTITUTE OF TECHNOLOGY
SELECTION OF FORGING EQUIPMENT
& STOCK SIZE FOR OPEN AND CLOSE DIE FORGING
• Classification of forging equipments & types
• Die impression
• Open & close die forging
• Flash & gutter
• Die design
• Variation of stroke with load
• Variation of FLR
• Design consideration of blocker & finisher
• Trim tool design & its consideration
CLASSIFICATION OF FORGING EQUIPMENTS
The most common type of forging equipment is the hammer and press.
The choice of forging equipment depends on a number of factors,
A. part size
C. material, and
D. quality of the parts to be produced.
Forging equipments can be classified in two categories
1. Work restricted machine
2. Stroke restricted machine
1. WORK RESTRICTED MACHINES
In work restricted machines the amount of deformation that can be achieved during
each stroke or blow of the machine is limited by the energy or maximum force
available. Machines that fall into this category are .
b. Friction screw presses
c. Hydraulic presses.
a. Gravity drop hammer.
The principle of operation is that the moving die block is raised by a lifting mechanism and
then released, so that it falls onto the fixed die attached to the anvil. This potential energy is
converted into kinetic energy as the die block falls and is then dissipated in deformation of
the work piece.
These machines are available in a range of blow energies from 0.6kNm (60kgm) to 400 kNm
b. DOUBLE ACTING OR POWER HAMMERS:
These machines are similar to gravity hammers in that a lifting cylinder raises
the moving tup, but power is also applied to the downward-moving tup to
increase the energy capacity. Energy ratings for similar tup weights are
considerably more than for gravity hammers, and the die closing speeds are
higher also. Double-acting hammers are manufactured in a range of energy
ratings from 3 kN-m (300 kg-m) to 825 kN-m (82,500 kg-m).
c. VERTICAL COUNTERBLOW HAMMERS:
In these machines two tups with nearly equal masses are driven by double-
acting cylinders toward each other and impact in the center of the machine.
Very high energy capacities are available in the largest machines, with
ranges from 30 kN-m (3 0,000 kg-m) to 2000 kN-m (200,000 kg-m).
d. HORIZONTAL COUNTERBLOW HAMMERS:
These machines are also called impacters and two rams are actuated by double
acting cylinders. Heated stock is positioned vertically between the dies by an
automatic transfer mechanism. Energy ranges from 4 kN-m (400 kg-m) to 54
kN-m (5400 kg-m) are typical.
2. SCREW PRESSES:
In screw presses, the upper ram and die are connected to a large vertical screw
that can be rotated by a flywheel, so that the ram can move up and down
relative to the fixed die in the bed of the machine. The ram has a limited
amount of energy for each stroke, thus multiple blows are usually employed
similar to hammers. Screw presses are available in ratings from 0.63 MN to 63
MN (63-6300 tons).
3. HYDRAULIC PRESSES:
Hydraulic presses are available in a wide range of sizes up to the largest at
50,000 tons or more capacity. The moving die is attached to a ram actuated by
a large hydraulic cylinder (Fig. 14.18d). Various strokes, forces, and closing
speeds can be obtained on hydraulic presses. In some cases hydraulic presses
are fitted with auxiliary horizontally moving rams, and these enable side
depressions to be forged into some parts, although this is not done to a great
STROKE RESTRICTED MACHINES:
In stroke-restricted machines the amount of deformation that can be done is
fixed by the stroke of the machine. If sufficient force or energy to carry out the
operation is not available, then the machine will stall and a larger machine
should be used. Mechanical presses fall into this category, as a crank or
eccentric determines the amount of ram movement.
1. MECHANICAL PRESSES:
The mechanical press transforms the rotational force of a motor into a
translational force vector that performs the pressing action. Therefore, the
energy in a mechanical press comes from the motor.
These types of presses are generally faster than hydraulic or screw presses,
(actually the screw press may also be classified as a mechanical press).
When performing a manufacturing operation using a mechanical press, the
correct range of the stroke is essential.
In mechanical presses, a crank, knuckle joint, scotch yoke, or moving-
wedge mechanism is used to apply a vertical squeezing motion between the
upper moving die and a lower fixed die, as shown in
• Open-die forging is carried
out between flat dies or dies of
very simple shape.
• The process is used for
mostly large objects or when
the number of parts produced
• Open-die forging is often
used to perform the work-
piece for closed-die forging.
Closed-die forging (or impression-die forging)
• The work-piece is deformed
between two die halves which carry
the impressions of the desired final
• The work-piece is deformed under
high pressure in a closed cavity.
• Normally used for smaller
• The process provide precision
forging with close dimensional
• Closed dies are expensive.
FLASH AND GUTTER
Initially it restrict the metal going out from cavity
After filling cavity it allows the excess metal to go outside from cavity in last portion of
To accumulate extra material coming out from die.
Design consideration of blocker
1. Volume of blocker should be more as compare to
2. Rapid change in dimensions is to avoided.
3. Fillet and corner radii should be large.
4. Length and Width are less.
5. Depth is more.
6. Draft angle is same.
7. Flash and gutter impression are not required.
Design consideration for finisher
1. Dimension of finisher will be as per forging drawing.
2. Volume is less.
3. Length and width is to be less.
4. Depth is less.
5. Rapid change in dimension may be possible. i.e. minimum fillet corner
any required radii may be provided to enhance are yield.
6. Draft angle remains same.
7. Flash and gutter impressions are necessary.
Trim tool design
1. Die material : Mild steel stalite on edge.
2. Profile of the trimming die should be similar to bottom finisher.
3. Flash and gutter impression to be provided in thin die.
4. Material inside the cavity to be hammered out so that component may
5. Stalite should be given on cutting edge and other portion can be made of
mild steel. So welding of stalite should be attach to the mild steel.
6. Cutting edge is made by machining (milling/grinding) on weld surface.
7. Cutting edge thickness is kept at least 1.5 times flash thickness to have
8. Trimming die should fitted with the shoe. Shoe should have more no. of
Design consideration for trim punch
1. Punch Material : Die steel.
2. Profile for punch is similar so that of finisher top.
3. Material outside the cavity is to be machined.
4. Punch is fitted with plate with the help of threaded
5. Stripper plate is used to avoid sticking of trimmed
flash with punch during its return stroke.
6. Total height of the trimming tool should be greater
than shut height plus flash thickness.