Manufacturing is the process of turning raw materials into finished goods using machinery, tools, and labor. But "manufacturing" is a broad term — the specific steps and equipment used to make a product vary widely depending on the material, design, volume, and end use.
A manufacturing process describes the method used to shape, form, cut, join, or finish a part or product. Each process relies on different technology and serves a different purpose. Some are ideal for high-volume production, others for complex one-off parts.
Understanding the different manufacturing processes helps engineers, product designers, and procurement teams select the right method for their project — which directly impacts cost, lead time, quality, and performance.
Below, we'll break down 7 common manufacturing processes, how they work, and when each one is used.
Casting is one of the oldest manufacturing processes, dating back thousands of years. It works by pouring a liquid material — usually molten metal — into a mold cavity. The material fills the shape of the mold, cools, and solidifies into the finished part (called a casting).
There are several casting methods. Die casting uses high pressure to inject molten metal into a steel die, producing parts with tight dimensional accuracy at high volumes. Sand casting uses a sand-based mold that's destroyed after each pour, making it better for larger parts or lower volumes. Investment casting (also called lost-wax casting) creates highly detailed parts by building a ceramic mold around a wax pattern.
Common materials: Aluminum, zinc, iron, steel, bronze, and copper alloys. Non-metal materials like concrete, epoxy, and plaster can also be cast.
Industries and applications: Automotive (engine blocks, transmission housings), aerospace (turbine blades), construction (pipe fittings), and consumer goods (cookware, hardware). Parts with complex internal geometries or irregular shapes are often good candidates for casting.
Advantages: Casting can produce complex shapes that would be difficult or impossible to machine from solid stock. Tooling is reusable, so per-unit costs drop significantly at higher volumes.
Limitations: Surface finish and dimensional tolerances are generally looser than machined parts. Castings often require secondary operations like machining, grinding, or heat treatment to meet final specifications.
Molding is similar to casting in concept — material is shaped inside a mold — but it typically uses plastics, rubber, glass, or composites instead of metal.
Injection molding is the most widely used molding process. Plastic pellets are heated until molten, injected into a steel mold under high pressure, cooled, and ejected. It's built for mass production — once the mold is made, the process can produce thousands or millions of identical parts with very low per-unit cost.
Blow molding is used to create hollow plastic parts, like bottles and containers. A heated tube of plastic (called a parison) is inflated inside a mold, taking its shape as it cools. Compression molding presses raw material into a heated mold cavity and is commonly used for rubber and thermoset plastics. Rotational molding slowly rotates a mold filled with powdered plastic in an oven, coating the interior walls to create large hollow parts like tanks and kayaks.
Common materials: Thermoplastics (ABS, nylon, polycarbonate, polyethylene), thermoset plastics, rubber, silicone, and fiberglass.
Industries and applications: Consumer products, packaging, automotive interiors, medical devices, electronics housings, and toys. If you've held a plastic product today, it was almost certainly molded.
Advantages: Extremely high production volumes at low per-unit cost. Consistent part quality and repeatability. Wide range of material and color options.
Limitations: High upfront tooling costs (injection molds can cost tens of thousands of dollars). Design changes after tooling are expensive. Primarily limited to plastics and polymers.
Forming (or metal forming) reshapes a piece of material — typically metal — without adding or removing any material. The part's mass stays the same; only its geometry changes.
There are two broad categories. Compressive forming applies force to reshape the material by pressing, rolling, or hammering. This includes:
Tensile forming stretches the material. Drawing pulls sheet metal into a die cavity to create cup-shaped or box-shaped parts (like aluminum cans). Stretch forming clamps and stretches sheet metal over a die.
Common materials: Steel, aluminum, copper, brass, titanium, and other metals and alloys.
Industries and applications: Automotive (body panels, structural components), aerospace (fuselage skins, brackets), construction (structural beams, metal roofing), and consumer goods (utensils, cans, hardware).
Advantages: Forming can produce parts very quickly, especially in stamping operations. The process often improves material strength through work hardening. Material waste is minimal compared to subtractive processes.
Limitations: Tooling (dies, presses) can be expensive. Part geometry is limited by what the material can be shaped into without cracking or tearing. Tight tolerances are harder to achieve than with machining.
Machining is a subtractive manufacturing process — it starts with a solid block or bar of material and removes material through cutting, drilling, grinding, or turning to create the finished part.
Today, most machining is performed on CNC (computer numerical control) machines. A part is programmed using CAD/CAM software, and the machine follows those instructions with very little human intervention. CNC machines can operate on multiple axes simultaneously, making them capable of producing highly complex geometries.
Common machining operations include:
Common materials: Steel, stainless steel, aluminum, brass, copper, titanium, Inconel, plastics, and many other metals and alloys. Machining is one of the most versatile processes in terms of material compatibility — see a full list of machinable materials.
Industries and applications: Aerospace, defense, medical devices, energy, industrial equipment, instrumentation, and precision components across nearly every industry. Any time a part requires tight tolerances, complex geometry, or excellent surface finish, machining is typically the process of choice.
Advantages: Exceptional dimensional accuracy and repeatability. Can hold tolerances as tight as ±0.0005" or tighter. Works with a very wide range of materials. Flexible — the same machine can produce different parts with a program change, making it efficient for both prototype and production volumes.
Limitations: Produces material waste (chips and swarf). Per-unit cost is higher than casting or molding at very high volumes. Cycle time can be longer for highly complex parts.
Joining connects two or more separate parts or components into a single assembly. It's typically a secondary operation — the individual parts are made first using another process (machining, casting, forming, etc.), then joined together.
Welding fuses materials together using heat, pressure, or both. There are many welding methods — MIG, TIG, stick, laser, and electron beam welding are among the most common. Welding creates a permanent bond and is used extensively in structural, automotive, and heavy equipment applications.
Soldering and brazing use a filler metal with a lower melting point to bond parts without melting the base materials. Soldering is standard in electronics manufacturing; brazing is used for plumbing, HVAC, and joining dissimilar metals.
Mechanical fastening uses screws, bolts, rivets, pins, or clips to hold parts together. Unlike welding, mechanical joints are typically designed to be disassembled for maintenance, cleaning, or part replacement.
Adhesive bonding uses industrial adhesives or epoxies. It distributes stress more evenly than point fasteners and can join dissimilar materials (metal to plastic, for example), but the bond is generally weaker than welding under high loads.
Industries and applications: Construction (steel structures), automotive (body assembly, exhaust systems), aerospace (airframe assembly), electronics (circuit board soldering), and virtually any industry that produces multi-component assemblies.
Advantages: Allows complex assemblies that would be impossible to make as a single piece. Different joining methods offer different tradeoffs between strength, permanence, cost, and disassembly.
Limitations: Joints can be points of failure under stress or fatigue. Welding introduces heat-affected zones that can alter material properties. Quality depends heavily on operator skill (especially in welding).
Surface treatment processes modify the exterior of a part — either for functional purposes (protection, durability, conductivity) or for identification and aesthetics. These are almost always secondary operations performed after the part's geometry is complete.
Finishing and coating processes include:
Marking and labeling processes include laser engraving, CNC engraving, chemical etching, and pad printing. These are used to add serial numbers, part numbers, logos, calibration markings, and regulatory information.
Industries and applications: Marking and finishing are used across all manufacturing industries. Parts that operate in corrosive environments, require traceability, or need to meet cosmetic standards will typically go through one or more surface treatment processes.
Advantages: Improves part longevity, corrosion resistance, wear resistance, and appearance. Marking adds traceability — critical for aerospace, defense, and medical applications.
Limitations: Adds cost and lead time. Some coatings change dimensional tolerances slightly, which must be accounted for in design.
Additive manufacturing builds parts layer by layer from a digital model, rather than removing or reshaping material. It's the newest of the major manufacturing processes and has advanced rapidly over the past decade.
FDM (Fused Deposition Modeling) extrudes melted thermoplastic filament through a nozzle, building the part one layer at a time. It's the most accessible method and is common in prototyping and hobbyist applications. SLA (Stereolithography) uses a UV laser to cure liquid photopolymer resin, producing parts with finer detail and smoother surfaces. SLS (Selective Laser Sintering) uses a laser to fuse powdered material (nylon, other polymers, or metal powders) layer by layer. DMLS (Direct Metal Laser Sintering) and EBM (Electron Beam Melting) are metal additive processes used in aerospace and medical applications.
Common materials: PLA, ABS, nylon, PETG, photopolymer resins, and (increasingly) metals like titanium, stainless steel, aluminum, and Inconel.
Industries and applications: Prototyping and product development, aerospace (lightweight structural parts), medical (custom implants, surgical guides), dental, automotive, and tooling. 3D printing is particularly well-suited for rapid prototyping, low-volume production, and parts with complex internal structures (like lattices or cooling channels) that can't be made with traditional methods.
Advantages: No tooling required — go straight from CAD to part. Design freedom to create geometries impossible with subtractive or formative methods. Cost-effective for low volumes and one-off parts. Rapid iteration during product development.
Limitations: Slower than machining or molding for production quantities. Material options are more limited. Parts often require post-processing (support removal, sanding, curing). Mechanical properties and surface finish generally don't match machined or molded parts, though metal additive is closing the gap.
There's no single "best" manufacturing process — the right choice depends on several factors:
In practice, many finished products use multiple manufacturing processes. A part might be cast to get its rough shape, machined to bring critical features into tolerance, finished with a surface treatment for corrosion resistance, and then joined with other components in a final assembly.
A manufacturing process is the specific method or series of steps used to transform raw materials into a finished product. This includes shaping, cutting, joining, and finishing operations performed using machinery, tools, and labor.
The 7 major types of manufacturing processes are casting, molding, forming, machining, joining, surface treatment (coating and finishing), and additive manufacturing (3D printing). Each uses different methods and equipment to shape or modify materials.
CNC machining is the most common process used when tight dimensional tolerances are required. CNC milling and turning can hold tolerances as tight as ±0.0005" or better, and grinding can achieve even tighter finishes. Casting and forming often require secondary machining to meet precision requirements.
Forming (also called metal forming) reshapes a workpiece without adding or removing material. Processes like rolling, forging, stamping, and extrusion apply force to change the shape of the material while keeping its mass the same.
Subtractive manufacturing (machining) starts with a solid block of material and removes material to create the part. Additive manufacturing (3D printing) builds the part up layer by layer from raw material. Subtractive processes generally offer better tolerances and material properties; additive offers more design freedom and doesn't require tooling.
Both casting and molding involve filling a mold cavity with material and allowing it to solidify. The main difference is the material: casting typically uses molten metal, while molding typically uses plastics, rubber, or glass. The equipment, temperatures, and pressures involved are also different.
Many products require multiple manufacturing processes to go from raw material to finished part — and precision machining is at the center of most of them.
At Spex, we specialize in CNC machining for OEMs across aerospace, defense, energy, instrumentation, and industrial equipment. Whether you need precision-machined components from a wide range of materials, secondary operations like engraving or finishing, or a supply chain partner that manages the full production process — we can help.
We've been manufacturing precision parts since 1946 and are ISO 9001:2015 certified.
Request a quote or reach out to our team to discuss your next project.
