High energy rate forming (HERF) is a sheet metal forming process that forms products at very high velocities and pressures. It uses a short burst of high energy transmitted through a medium to the workpiece, forcing it into a die cavity. This allows materials to be formed beyond their normal limits with minimal springback. Some key advantages are higher production rates, lower die costs, and the ability to form difficult metals. Common HERF processes are explosive forming, electrohydraulic forming, and magnetic pulse forming.

1. UNIT IV
SHEET METAL FORMING &
UNCONVENTIONAL FORMING
PROCESS

2. HIGH ENERGY RATE FORMING
PROCESS [HERF ]
 It is a process that form products at very high
velocities and extremely high pressure

3.  Large amount of energy is applied for a very
short interval of time.
 High particle velocities are produced in contrast
with conventional forming process. The velocity
of deformation is also very large and hence these
are also called High Velocity Forming (HVF)
processes.
 HERF process used short burst of energy that is
transmitted to the part surface through a medium
(water/air).
 The resulting force or shockwave acts to force the
part into a die cavity that has the desired shape of
finished product.
 Materials being formed beyond their usual limits

4.  High energy required for small interval time.
 Many metals tend to deform more rapidly under
extra fast application of load which make these
processes useful to form large size parts out of
these most metals including those which are difficult
to form.
 Material that are difficult to form in conventional
methods due to spring back effect will undergo large
plastic deformation with almost no spring back effect
when HERF is used.

5. Advantages of HERF
Processes
 Production rates are higher, as parts are made at a
rapid rate and thus these process are also called high
velocity forming process.
 Die costs are relatively lower.
 it is possible to form most metals including difficult to
form metals.
 No or minimum spring back effect on the material
after the process.
 Production cost is low as power hammer (or press) is
eliminated in the process.
 Complex shapes / profiles can be made much easily,
as compared to conventional forming.

6.  Suitable for a range of production volume such as
small numbers, batches or mass production.
Limitations:
 Not suitable to highly brittle materials.
 Source of energy (chemical explosive or electrical)
must be handled carefully.
 Highly skilled personnel are required from design to
execution.
 Dies need to be much bigger to withstand high
energy rates and shocks and to prevent cracking.

7. Applications:
 In ship building – to form large plates / parts (up
to 25 mm thick).
 Bending thick tubes/ pipes (up to 25 mm thick).
 Radar dish
 space applications

8. TYPES OF HERF PROCESSES
1. EXPLOSIVE FORMING
2. ELECTRO HYDRAULIC FORMING
3. MAGNETIC PULSE FORMING