26 Common Metal Forming Processes Explained

Metal manufacturing is one of the most important industries in modern production. Whether you are custom-machining metal prototypes, aircraft parts, or everyday tools, understanding the different metalworking methods can help you choose the right technology for your project.

Each manufacturing process offers unique benefits and works best for specific applications. Some methods excel at creating complex shapes, while others provide better strength or lower costs. Let's explore these essential metalworking techniques that power manufacturing worldwide.

This article will guide you through the main processes used for forming and machining metal products, from traditional casting methods to modern laser technology.

Casting Processes

Die Casting

Die casting pushes molten metal into mold cavities under high pressure. Manufacturers create molds from high-strength alloys, similar to how plastic injection molding works. This process produces custom metal parts with excellent surface finish and tight tolerances, making it popular for automotive and consumer products.

Sand Casting

Sand casting uses sand molds to shape custom machined metal parts. Workers place a pattern (either a finished part or wooden model) into sand, then pack sand around it. After removing the pattern, the sand forms a mold cavity. The process requires creating channels for pouring metal and releasing gases. Since the sand mold breaks apart when removing the finished part, each casting needs a fresh mold.

Investment Casting

Also called lost-wax casting, this method involves several steps: wax pressing, wax repair, tree assembly, slurry coating, wax melting, metal pouring, and finishing. Workers first create a wax pattern of the desired part, then coat it with ceramic slurry to form a shell. After the shell dries, heating melts away the wax, leaving only the ceramic mold. Pouring molten metal through pre-made gates fills the cavity, and cooling produces the final part.

Pressure Casting

This technique fills molds with liquid or semi-liquid metal at high speeds under pressure. The metal shapes and solidifies under continuous pressure, creating dense, strong castings with minimal defects.

Low Pressure Casting

Low-pressure gas forces liquid metal into molds, where it solidifies into finished parts. Originally developed for aluminum alloy products, this method now extends to copper, iron, and steel castings requiring higher melting points.

Centrifugal Casting

Pouring liquid metal into rapidly spinning molds uses centrifugal force to fill the cavity and form parts. Depending on the part's shape, size, and production volume, manufacturers choose different mold types, including sand, shell, investment shell, metal molds, or metal molds with coating layers.

Evaporative Pattern Casting

This process bonds paraffin or foam patterns matching the part's dimensions into clusters, coats them with refractory material, and buries them in dry quartz sand. Pouring metal under vacuum vaporizes the pattern, allowing liquid metal to take its place. After cooling, the result is a near-net-shape casting. This method eliminates draft angles, parting lines, and cores, reducing defects and dimensional errors.

Squeeze Casting

Sometimes called liquid forging, squeeze casting pours molten or semi-solid metal directly into open dies, then closes the dies to create flow and fill the part shape. High pressure applied to the solidified shell causes plastic deformation, while unsolidified metal experiences isostatic pressure and high-pressure solidification. Indirect squeeze casting injects metal into closed dies through a punch under high pressure for crystallization and solidification.

Continuous Casting

This method continuously pours liquid metal into one end of a through-mold while extracting formed material from the other end, creating a steady stream of cast products.

Forging and Forming Processes

Forging

Forging applies pressure to metal blanks using forging machinery, causing plastic deformation to achieve specific shapes, sizes, and mechanical properties. This process eliminates casting defects like porosity, optimizes microstructure, and preserves complete metal flow lines. Forgings typically show better mechanical properties than castings of the same material, making them ideal for high-load, demanding applications.

Die Forging

Specialized die forging equipment uses dies to shape blanks into forgings. Methods include hammer forging, crank press forging, flat forging, and friction press forging. Roll forging rotates opposing dies to plastically deform material into required forgings or blanks, representing a special type of longitudinal rolling.

Rolling

Rolling (or milling) passes metal ingots through paired rollers to shape them. When metal temperature exceeds its recrystallization temperature during rolling, the process is "hot rolling"; otherwise, it's "cold rolling." Rolling remains the most common metalworking method.

Drawing

Drawing pulls metal through dies smaller than the original cross-section using force applied to the front end, producing desired shapes and sizes. Since drawing typically occurs cold, it's also called cold drawing.

Stamping

Presses and dies apply force to sheets, strips, tubes, and profiles, causing plastic deformation or separation to obtain workpieces of required shapes and sizes.

Typically, custom metal casings and sheet metal parts are produced using a stamping process, which is faster and achieves higher dimensional accuracy.

Metal Injection Molding

Derived from plastic injection molding, this powder metallurgy technique produces complex shapes economically. Adding metal or ceramic powders to plastic improves strength and wear resistance. The process maximizes solid particle content, then removes binders during sintering and densifies the formed blank.

Roll Forming

Continuous roller stands progressively shape stainless steel into complex forms. Each stand's roller profile continues to deform the metal until it achieves the final shape. Complex parts may require thirty-six stands, while simple parts need only three or four.

Die Cutting

This blanking process positions formed film on punch dies, then closes the die to remove excess material while preserving the 3D product shape, matching the cavity.

Blade Die Cutting

This method positions film panels or circuits on base plates while fixing blade dies to machine templates. Machine pressure controls the blade cutting through material. Unlike punch cutting, blade cutting produces smoother edges and can create creases or partial cuts by adjusting pressure and depth. Dies cost less and offer more convenient, safe, and fast operation.

Machining Processes

Turning

Turning uses lathes where cutting tools shape rotating workpieces. Lathes primarily machine shafts, discs, sleeves, and other parts with rotating surfaces.

Turning represents the most basic and common high-precision CNC technology, ideal for processing rotating surfaces, including cylinders, cones, end faces, grooves, threads, and formed surfaces.

Milling

Milling is one of the most commonly used processes in Custom Metal Fabrication Prototype. Milling fixes blanks while high-speed rotating milling cutters remove material to create desired shapes and features. Traditional milling handles simple contours and slots, while CNC mills process complex shapes. Milling centers perform three-axis or multi-axis operations for molds, fixtures, thin-walled curved surfaces, prosthetics, and blades.

Planing

Planing uses planers making horizontal reciprocating motions relative to workpieces for cutting, mainly processing part profiles. Planing accuracy reaches IT9-IT7 with surface roughness of Ra 6.3-1.6um.

Grinding

Grinding removes excess material using abrasives and grinding tools, representing one of the most widely applied cutting methods.

Metal 3D Printing

Selective Laser Melting

Computer-controlled high-power CO₂ lasers selectively scan metal powder surfaces in powder-filled chambers. Where lasers strike, surface powder completely melts and fuses together, while unaffected areas remain powdered. The entire process occurs in sealed chambers filled with inert gas.

Selective Laser Sintering

SLS uses infrared lasers with powder materials. After preheating the powder slightly below its melting point, leveling rollers spread it flat. Computer-controlled lasers selectively sinter based on layer cross-section information. After completing all layers and removing excess powder, sintered parts emerge. Mature materials include wax and plastic powders, while metal and ceramic powder processes remain under development.

Metal Deposition

Similar to "toothpaste squeezing" fusion deposition, this process sprays metal powder. Nozzles simultaneously provide high-power lasers and inert gas protection while depositing metal powder. This method isn't limited by powder box size, enabling larger components and precise repair of damaged precision parts.

Conclusion

Metal manufacturing encompasses diverse processes, each suited for different applications, materials, and production requirements. Casting methods like die casting and investment casting excel at complex shapes, while forging produces superior strength. Modern machining offers precision finishing, and advanced technologies like selective laser melting enable innovative designs.

As a Custom Metal Fabrication Online service provider, LVMA always selects the right manufacturing processes for our clients. Understanding these fundamental processes helps engineers and manufacturers make informed decisions, optimize production efficiency, and produce high-quality metal products that meet precise specifications.