The forming process of mechanical parts is the process of transforming raw materials into parts with specific shapes, dimensions, and properties. Its selection and application directly determine the precision, mechanical properties, and production costs of the parts. In the field of mechanical manufacturing, forming processes not only encompass traditional hot and cold working methods but also modern precision forming and composite manufacturing technologies. Various processes form a complementary system based on material properties, structural complexity, and batch requirements, providing support for the efficient production of different types of parts.
Casting is a long-established and widely applicable forming method, suitable for manufacturing parts with complex structures and hollow or irregular shapes. Sand casting can produce large, heavy parts, such as shells and bases; metal mold casting and pressure casting can achieve high dimensional accuracy and surface finish, and are often used for small to medium-sized high-strength parts. The key to casting processes lies in melting control, mold design, and solidification process management. A reasonable gating system and cooling path can reduce shrinkage cavities, porosity, and stress concentration, and improve density and uniformity.
Forging uses external force to plastically deform metal billets, resulting in a dense fibrous structure and excellent mechanical properties. It is widely used in load-bearing components such as shafts, gear blanks, and high-strength connectors. Free forging is suitable for single-piece or small-batch production and can flexibly form large components; die forging, on the other hand, is formed within a closed die, offering higher precision and production efficiency, suitable for mass production of complex-shaped parts. The forging process requires precise control of heating temperature and deformation rate to avoid overheating, cracking, and folding defects, while preserving the desired grain flow to enhance fatigue resistance.
Machining is the primary means of achieving high-precision dimensions and surface quality in mechanical parts, including turning, milling, drilling, grinding, and multi-axis machining. This method can correct billet shape deviations, achieving strict tolerance fits and fine surface textures, and is commonly used for the final forming of bearings, guide rails, gears, and precision structural components. The core of the machining process lies in tool selection, cutting parameter optimization, and cooling and lubrication management, balancing efficiency and surface integrity, and preventing microscopic damage caused by cutting heat or vibration.
Stamping and cold heading processes offer significant advantages in the production of sheet metal and wire-based components. Stamping utilizes a press and dies to complete shearing, bending, and stretching processes in one or consecutive steps, making it suitable for mass production of housings, connecting plates, and spring sheets. Cold heading, on the other hand, locally upsets metal wire at room temperature, producing high-strength head and rod structures, widely used in fasteners such as screws and rivets. These processes save materials and offer fast production speeds, but require high precision in dies and high material ductility.
With advancements in manufacturing technology, precision forming and additive manufacturing are emerging in the production of complex components. Precision casting and powder metallurgy can form near-net-shape components in one piece, reducing subsequent processing. Additive manufacturing (3D printing) breaks through the limitations of traditional subtractive and equal-material forming, demonstrating advantages in the production of special components with internal flow channels, lattice structures, or gradient materials. However, these processes still require continuous research and development in areas such as material performance consistency, surface quality improvement, and post-processing refinement.
The selection of forming processes should comprehensively consider the functional requirements of the components, material characteristics, structural complexity, production volume, and cost constraints. In actual production, a combination of multiple processes is often used. For example, a near-shaped billet is first obtained by casting or forging, and then the final precision and performance requirements are achieved through cutting and heat treatment. This organic connection of the process chain can not only give full play to the advantages of various methods, but also effectively ensure the quality stability and service reliability of mechanical parts, providing solid technical support for modern manufacturing.
