Drop Forging – A Metal Forming Process used to Make Quality Components

31 May, 2022
Drop Forging – A Metal Forming Process used to Make Quality Components

Forging is the oldest known components manufacturing or metalworking process in which metals are given shape using localized compressive forces. The force is usually applied with a power hammer or a die. The components created using this process are stronger and more durable compared to components manufactured using other metalworking processes.

Thus, this forging is generally used where reliability and human safety is the biggest concern.  It is a metal forming process that is performed at high or ambient temperature employing either forging hammers or press tools. In this forging process, a hammer is raised and dropped into the work piece to deform it as per the die shape. Drop forging is characterized by the use of dies and machines that exert high forces and at the same time allow precise guidance of the tools. Different metals are suitable for drop forging after heating such as steel, magnesium, aluminum, stainless steel, brass, copper, as well as their alloys.

Drop Forging Process

It is a metal forming process in which a work piece is inserted into a die and hammered till it takes the shape of the die. The lower part is stationary whereas the upper part is a moving hammer that is dropped onto the work piece to deform it. The drop forging can be executed at both high and ambient temperatures. In the metal shaping industry, this manufacturing process has been in use for hundreds of years, and the mechanics of the process are still the same.

However, the machinery involved in the process has become advanced to make drop forging a high-precision manufacturing process. The material properties of the final piece are enhanced with drop forging like all other forging techniques. This metalworking process is different from upset forging, press forging, or any other forging processes, as in this process the billet is deformed into the desired shapes with the help of forging dies.

Advantages of Drop Forging

The drop forging process involving hot working metals has been used for thousands of years, as this metalworking process comes with multiple benefits. Drop forging has become a highly relied upon manufacturing method because of the reliable quality and strength of the parts or components manufactured.

Currently, the drop forging process has been mechanized with the latest technology development. This metalworking process is used for the production of a wide range of components that are used in a wide range of industries. Some of the major benefits of this process include:

  • This process produces a large number of components of top-most quality
  • This process makes the metal stronger than the original raw material ad also gives metals a high level of durability.
  • The components manufactured have good grain flow and surface finish.
  • There is little or no wastage of the material.
  • Components manufactured are of good strength and durable, as the grain is aligned along the line of potential stress.
  • This process is used to make complex-shaped metal parts.
  • This process saves metal material and reduces machining work, so in case of more batches, the spare parts cost will reduce.

The components or spare parts made with this process have enhanced mechanical properties

Types of Drop Forging

Drop forging is usually of two types, open-die drop forging and closed-die drop forging. As indicated by their names the difference is in the die shape, the open-die drop does not completely enclose the work piece whereas the closed-die drop completely encloses the work piece.

Open-die drop forging: Open-die drop forging doesn’t completely cover the work piece and allows deformation into open space. In this process, the metal is placed on the die by an operator, while a hammer strikes the metal. The work piece position is changed by the operator before every strike until the final shape is achieved. It is a popular component manufacturing process that imparts some vital features to the components such as greater strength, improved grain size, and continuous grain flow.

Characteristics of Open-Die Drop Forging

  • The production equipment used in the open-die drop forging is simple, and investment in equipment is also less compared to closed-dye drop forging.
  • Tooling and dies in open-die drop forging is not closed and hence it is also named free forging.
  • Open-die drop forging may produce a large component or spare parts weighing more than 10 tons.
  • Shapes of open-die drop forgings are not complicated and this type of forging is workable even for special shapes.

Closed-Die Drop Forging: In the closed-die drop forging, a closed die looks like a mold that is attached to the anvil in which metal is placed. When the shaped hammer dies strike the workpiece, the material flows and fills the die cavities. In this process, the hammer is dropped in quick succession until the desired shape is achieved. Sometimes the series of diverse cavities are used to give some specific shape. The initial investment in this process is high because of the specific design of the die cavities. Thus, manufacturing closed-die drop-forged parts in more volume turn out to be more economical. This forging process is generally used in the tooling and automotive industries.

Characteristics of Closed Die Drop Forgings:

  • The production capacity is high in closed-die drop forgings because the steel bar can be quickly forged under the press of upper and lower dies.  
  • Components produced with this forging process have accurate dimensions due to the perfect mould that prevents further machining thereby saving lots of costs.
  • There is no chance of the defects in the components because the mechanical property of drop forging is better compared to casting.

Typical Drop Forged Components

Components and spare parts produced with drop forged process are used across several industries such as automotive, aerospace, defense, agriculture, and material handling. Some of the popular components produced with this process are:

  • Levers
  • Gears
  • Railroads
  • Crankshafts
  • Connecting rods
  • Pedal cranks
  • Gear blanks
  • Spanners