Metal forming is a fundamental process in manufacturing, shaping raw metal into functional and intricate parts. From the simple bending of a sheet to the complex forging of an engine component, these methods are the backbone of industries ranging from automotive and aerospace to construction and consumer goods. This comprehensive guide explores 19 common metal forming methods.
Planing
Planing is a cutting method in which a planer performs horizontal, linear reciprocating motion on a workpiece. It is primarily used for contour machining of parts. Planing accuracy is IT9 to IT7, with a surface roughness Ra of 6.3 to 1.6 μm.
Grinding is a process that uses abrasives and tools to remove excess material from a workpiece. Grinding is one of the most widely used cutting methods.
Selective Laser Melting
In a tank filled with metal powder, a computer controls a high-powered CO2 laser beam, selectively sweeping across the powder’s surface. Wherever the laser strikes, the surface metal powder completely melts and fuses, while areas not touched remain powdery. The entire process takes place in a sealed chamber filled with inert gas.
Selective Laser Sintering (SLS)
This SLS method uses an infrared laser as the energy source, primarily using powdered materials. During processing, the powder is first preheated to a temperature slightly below its melting point, then flattened using a flattening rod. The laser beam, under computer control, selectively sinters the layers based on the cross-sectional information of the layers. After each layer is sintered, the next one is sintered. After all layers are sintered, the excess powder is removed, resulting in a sintered part. Currently, the materials used for this process are wax powder and plastic powder, but sintering with metal or ceramic powders is still under research.
Metal Deposition
Similar to melt deposition, a process known as “cream squeezing” (likely referring to a process called melt deposition), this method produces metal powder. The nozzle simultaneously delivers the metal powder while providing a high-power laser and inert gas shield. This eliminates the limitations of the powder tank size, allowing for the direct production of larger parts. It is also well-suited for repairing damaged precision parts.
Roll Forming
The roll forming method uses a series of continuous roll stands to roll stainless steel into complex shapes. The roll sequence is designed so that the roll profiles of each stand continuously deform the metal until the desired final shape is achieved. Complex part shapes can use up to thirty-six roll stands, but simpler parts can be made with only three or four.
The roll forming method uses a series of continuous roll stands to roll stainless steel into complex shapes. The roll sequence is designed so that the roll profiles of each stand continuously deform the metal until the desired final shape is achieved. Complex part shapes can use up to thirty-six roll stands, but simpler parts can be made with only three or four.
Die forging is a forging method that uses dies on specialized forging equipment to form a blank into a forged piece. This method produces forgings with precise dimensions, minimal machining allowances, complex structures, and high productivity.
Die Cutting
Die Cutting is the blanking process where the film, formed in the previous process, is positioned on the male die of the punching die. The die is then closed to remove excess material, preserving the product’s 3D shape and matching it to the mold cavity.
Die-cutting Process – Die
Die-cutting involves positioning a film panel or circuit board on a base plate, securing a die cutter to the machine’s template, and using the downward pressure of the machine to control the blade to cut the material. This method differs from punching in that it produces smoother cuts. Adjusting the cutting pressure and depth allows for effects such as indentations and partial cuts. Furthermore, die cutting costs are low, and operations are more convenient, safe, and efficient.
Centrifugal Casting
Centrifugal casting is a technique and method in which liquid metal is poured into a high-speed rotating mold, causing the molten metal to fill the mold and form the casting under the action of centrifugal force. Depending on the shape, size, and production batch of the casting, the mold used for centrifugal casting can be a non-metallic mold (such as a sand mold, shell mold, or investment shell mold), a metal mold, or a metal mold coated with a coating or resin sand layer.
Lost Foam Casting
Lost foam casting (LFC) involves bonding wax or foam patterns of similar size and shape to the casting into a cluster. After applying a refractory coating and drying, the cluster is embedded in dry quartz sand and vibrated to form the pattern. Poured under negative pressure, the pattern vaporizes, allowing liquid metal to occupy the mold’s position. After solidification and cooling, the casting forms. Lost foam casting (LFC) is a new process that produces near-zero stock and precise molding. It requires no mold removal, parting surfaces, or sand cores, resulting in castings free of flash, burrs, or draft angles, while minimizing dimensional errors caused by core assembly.
Squeeze Casting
Squeeze casting, also known as liquid die forging, involves pouring molten metal or a semi-solid alloy directly into an open mold. The mold is then closed to create a filling flow that takes the shape of the part. High pressure is then applied to plastically deform the solidified metal (the outer shell), while the unsolidified metal is subjected to isostatic pressure, simultaneously solidifying under high pressure. This results in a finished part or blank. This is known as direct squeeze casting. Indirect squeeze casting involves injecting molten metal or a semi-solid alloy into a sealed mold cavity through a punch and applying high pressure to crystallize and solidify it under pressure. This results in a finished part or blank.
Continuous Casting
Continuous casting is a casting method in which liquid metal is continuously poured into a through-mold at one end and the molded material is continuously drawn out from the other end.
Drawing
Drawing is a plastic working method in which an external force is applied to the front end of the metal being drawn, pulling the metal billet through a die hole smaller than the billet’s cross-section to produce a product of the desired shape and size. Because drawing is usually performed in a cold state, it is also called cold drawing or cold drawing.
Stamping
Stamping is a forming process in which a press and die are used to apply external forces to sheet metal, strip, tube, or profile, causing plastic deformation or separation, thereby producing a workpiece (stamped part) of the desired shape and size.
Metal Injection Molding
Metal Injection Molding (MIM) is a new powder metallurgy near-net-shape forming technology derived from the plastic injection molding industry. Plastic injection molding technology is well known for its ability to produce complex shapes at a low cost, but plastic products lack strength. To improve these properties, metal or ceramic powders can be added to the plastic to achieve higher strength and better wear resistance. In recent years, this concept has evolved to maximize the solid particle content and, during the subsequent sintering process, completely remove the binder and densify the preform. This new powder metallurgy forming method is called metal injection molding.
Lathing is a type of machining process that involves turning a rotating workpiece using a turning tool. Lathes are primarily used to machine shafts, disks, sleeves, and other workpieces with rotating surfaces. They are the most widely used type of machine tool in machinery manufacturing and repair shops. Turning involves cutting the workpiece on a lathe by rotating it relative to the tool.
Turning is the most basic and common cutting method and plays a crucial role in production. Turning is suitable for machining rotating surfaces. Most workpieces with rotating surfaces can be machined using turning methods, such as internal and external cylindrical surfaces, internal and external conical surfaces, end faces, grooves, threads, and rotating forming surfaces. The tools used are primarily turning tools.
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