Drop forging is a metal forming process. A workpiece is inserted into a die and then hammered until it has assumed the shape of the die. The lower die is a stationary part, while the upper part is a moving hammer dropped onto the workpiece in order to deform it. Drop forging can be performed both at high or ambient temperature. This manufacturing process has a long tradition in the metal shaping industry and it has been used for hundreds of years. The mechanics of the process are still the same, but all involved machinery has greatly advanced to turn drop forging into a high-precision manufacturing process. Similar to all other forging techniques, drop forging enhances the material properties of the final piece.
There are two main tools employed in forging machines to deform a stock through comprehensive forces. These are hammers or presses. Even though drop forging hammers and press machines deliver same results, the way force is delivered to the metal piece trough the forging die is fundamentally different. The main difference is that a forging hammer impacts the workpiece through successive strokes and not trough continuous pressure as a mechanical press. According to the way a hammer is attached and the way it deforms the workpiece, there are different types of forging hammers:
Drop Forging Hammers
The simplest configuration for forging is carried out on a specific hammer and anvil. A lower die is fixed on the anvil and an upper (moving) die is fixed on the ram. The ram and upper die transfer fast-speed kinetic energy to the work piece, placed in the lower die and anvil. The anvil configuration needs to provide a very solid base, since it absorbs a big amount of the energy. Therefore the anvils’ weight is usually ten to twenty times more than the weight of the hammer.
Double-acting Hammer at Setforge Estamfor
Counterblow Hammer at Setforge L'Horme
Double-Acting Forging Hammer
This configuration is similar to the first one, but the hammer fixed on the ram is accelerated when falling by air or steam; respectively – a hydraulic or pneumatic forging hammer. The double-acting forging hammers are very powerful and gradually replace the simpler configurations.
Counterblow Forging Hammers
This configuration doesn’t have an anvil, but two hammers fixed on two rams, moving in opposite directions, which permit precision forming of large workpieces. These are the most complex forging hammers and they allow very large forging energy levels to be achieved.
In terms of the position of the dies, there are two main types of drop forging: open-die drop forging and closed-die drop forging, also called impression-die forging.
Open-Die Drop Forging
As the name says, an open die doesn’t completely cover the workpiece and allows its deformation into open space. The metal stock is placed by an operator on the die, while the hammer is striking it. Before each strike the operator changes the position of the workpiece until the final desired shape is achieved. Open-die drop forging is a common manufacturing process, providing some important benefits as greater strength, improved grain size and continuous grain flow.
Closed-Die or Impression-Die Drop Forging
A closed die looks like a mold, attached to the anvil, in which the metal is placed. The hammer die is also shaped and when striking the workpiece the material flows and fills the die cavities. The hammer is dropped fast in very quick successions until the desired shape is achieved. Sometimes the shape requires the use of series of different cavities. Although the initial investment in closed-die equipment can be quite high because of the specific design of the dies cavities, closed-die drop forged parts become more economical with more volume. Therefore closed-die drop forging is often used in the automotive and tooling industries.
Benefits of Drop Forging
Drop forging delivers all common benefits typical in the forging manufacturing process. The most important ones include:
- Good surface finish
- Enhanced mechanical properties
- Recyclable flash
- Improved metal strength by aligning the grain along the lines of potential stress
Typical Drop Forged Components
Drop forged components are used in many industries, including automotive, aerospace, defence, agriculture or material handling. These can be among others:
- Connecting rods
- Pedal cranks
- Gear blanks
Farinia Group has a longstanding know-how in drop forging with hammers. Our forges are equipped with state-of-the art machinery and we employ high-qualified blacksmiths and top engineers. Farinia offers precision forging on simple, double-acting or counterblow forging hammers and best material selection. Our teams possess extended knowledge about the mechanical properties of every possible material and its ability to withstand failure or cracking.