what's Drop Forging? DNT Tools' use Forging Techniques
Drop forging is a kind of forging process different from press forging, upset forging or other forging processes. In drop forging, the billet is deformed into desired shapes with the help of forging dies. Types of drop forging are open-die drop forging and closed-die drop forging. The shape of the die is the main differences between open die drop forging and closed die drop forging like the names. Closed die drop forging does fully encloses the workpiece, while open die forging does not.
Closed Die Drop Forging
Closed die drop forging, or closed die forging, is a forging way that presses heated round metal bar into the shape we need under the pressure of the dies. It will ensure the accuracy of dimensions and little machining allowance, no structure limit, high production efficiency. General steps of closed die drop forging are: mould developing-raw material cutting-heating material-forging-trimming cutting-heat treatment-shot blasting-machining-surface treatment-package. Materials that applied in drop forging process can be stainless steel, alloy steel, carbon steel, copper and other forged materials.
Design of closed die drop forgings and tooling
The tooling or dies in closed die drop forging are usually made of tool steel. Tool steel will feature closed die forging dies with good impact resistance, high wear resistance, maintain strength at high temperatures, and can even withstand cycles of rapid heating and cooling. In order to produce a better, more economical die, we need to follow below:
1.The dies part along a single, flat plane whenever possible. If not, the parting plane follows the contour of the part.
2.The parting surface is a plane through the center of the forging and not near an upper or lower edge.
3.Adequate draft is provided; usually at least 3° for aluminium and 5° to 7° for steel.
4.Generous fillets and radii are used.
5.Ribs are low and wide.
6.The various sections are balanced to avoid extreme difference in metal flow.
7.Full advantage is taken of fiber flow lines.
8.Dimensional tolerances are not closer than necessary.
Typical characteristics of closed die drop forgings:
●Under the press of up and lower dies, we could forge the steel bar in fast time,so the production capacity is very high.
●With the help of accurate mould after machining, we could achieve higher accuracy dimensions,which will avoid further machining and save lots of cost.
●Comparing with casting, the mechanical propertity of drop forging will be better, defects can be effectively avoided.
Open Die Drop Forging
Open-die drop forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the billet, which is placed on a stationary anvil. Open-die forging gets its name from the fact that the dies do not enclose the workpiece, allowing it to flow except where contacted by the dies. The operator therefore needs to orient and position the workpiece to get the final shape. The dies are usually flat in shape, but some have a specially shaped surface for specialized operations. For example, a die may have a round, concave, or convex surface or be a tool to form holes or be a cut-off tool. Open-die forgings can be worked into shapes which include discs, hubs, blocks, shafts (including step shafts or with flanges), sleeves, cylinders, flats, hexes, rounds, plate, and some custom shapes. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work. In some cases, open-die forging may be employed to rough-shape ingots to prepare them for subsequent operations. Open-die forging may also orient the grain to increase strength in the required direction.
Closed Die Drop Forging vs Open Die Drop Forging
Investment in closed die forging equipments are much larger than open die forgings. Production equipments of open die forging is relatively simple.
Tooling & dies of closed die forging are enclosed, while it is opposite in open die forging. That is why open die forging is also named as free forging.
In terms of dimensions, closed die forging is used for small parts, while open die forging can produce large parts even more than 10 tons.
Shape of closed die forgings are much complicated than open die forging. Even though sometimes closed die forging is not workable for special shapes.