Casting remains one of the most versatile and cost-effective manufacturing processes for producing complex metal parts at scale. From automotive engine blocks to aerospace turbine blades, understanding the different types of casting processes helps engineers select the optimal method for their specific application requirements.
This comprehensive guide examines 14 distinct casting techniques, comparing their capabilities, limitations, and ideal use cases. Whether you're designing parts for ferrous metals like carbon steel or non-ferrous metals such as aluminum and copper alloys, choosing the right casting process directly impacts production costs, part quality, and manufacturing lead times.
Casting is a manufacturing process where molten metal or other liquid material is poured into a hollow cavity (mold) and allowed to solidify. Once cooled, the solidified part—called a casting—takes the shape of the mold cavity. This fundamental technique dates back thousands of years but evolved significantly during the Industrial Revolution when advances in metallurgy and mold-making enabled mass production of complex parts.
The basic casting process follows these steps:
Pattern Creation: A pattern replicating the final part geometry is created, typically from wood, metal, or plastic. The pattern includes allowances for shrinkage and machining.
Mold Making: The pattern forms a cavity in molding material (sand, metal, ceramic, or plaster). Two-part molds allow pattern removal before pouring.
Melting: Base metals or alloys are melted in furnaces at temperatures ranging from 1,100°F for aluminum to 2,800°F for carbon steel.
Pouring: Molten metal fills the mold cavity through gating systems designed to prevent turbulence and ensure complete filling.
Solidification: Metal cools and solidifies from the mold surfaces inward. Cooling rates affect grain structure and mechanical properties.
Shakeout & Finishing: After solidification, the casting is removed from the mold. Excess material (gates, risers, flash) is trimmed, and surfaces may be machined to final specifications.
Casting enables production of geometries impossible or uneconomical with other manufacturing processes. Complex internal passages, intricate external features, and large structural components all benefit from casting's design flexibility. Industries rely on casting for both prototyping and high-volume production, with processes ranging from sand casting's low tooling costs to die casting's exceptional production rates.
Automotive: Engine blocks, transmission housings, suspension components
Aerospace: Turbine blades, structural airframe parts, landing gear components
Construction: Pipe fittings, valves, heavy equipment components
Energy: Pump housings, valve bodies, turbine components
Medical: Surgical instruments, implant components, diagnostic equipment housings
Sand casting uses sand as the primary mold material, offering the most versatile and economical process for both ferrous metals and non-ferrous metals.
Lowest tooling costs (patterns are inexpensive)
Accommodates all metals and alloys
No size limitations (castings from ounces to hundreds of tons)
Suitable for low to medium production volumes
Rougher surface finish (125-500 microinches Ra)
Lower dimensional accuracy (±0.030" typical)
Slower production rates compared to permanent mold processes
Manual labor intensive for complex cores
Engine blocks, pump housings, large industrial machinery components, prototypes
Die casting forces molten metal under high pressure into precision steel molds (dies), producing dimensionally accurate parts at high production rates.
Excellent dimensional accuracy (±0.001-0.003")
Superior surface finish (63-125 microinches Ra)
Thin walls possible (0.030" minimum)
High production rates (100s-1000s parts/hour)
High tooling costs ($10,000-$100,000+ per die set)
Limited to non-ferrous metals (aluminum, zinc, magnesium)
Part size typically under 50 lbs
Porosity can occur without proper venting
Automotive components, consumer electronics housings, appliance parts, hardware
Investment casting (lost-wax casting) produces near-net-shape parts with exceptional surface finish and dimensional accuracy by using expendable ceramic molds.
Excellent surface finish (32-125 microinches Ra)
Tight tolerances (±0.003-0.005" per inch)
Complex geometries with undercuts
Minimal draft angles required (0.5° typical)
Higher costs than sand casting
Size typically limited to 2-200 lbs
Longer lead times (pattern production, shell building)
Not economical for very large production runs
Turbine blades, medical implants, jewelry, aerospace components, golf club heads
Gravity die casting (permanent mold casting) uses reusable metal molds with gravity-fed metal flow, balancing die casting's precision with lower equipment costs.
Better mechanical properties than sand casting (finer grain structure)
Good dimensional accuracy (±0.010-0.020")
Smooth surface finish (125-250 microinches Ra)
Faster cycles than sand casting
Higher tooling costs than sand casting
Limited to aluminum, magnesium, and copper alloys
Not suitable for complex internal passages
Maximum part weight typically under 100 lbs
Automotive wheels, cylinder heads, pistons, cookware
Continuous casting produces semi-finished metal products (billets, blooms, slabs) in continuous lengths, revolutionizing primary metal production since the Industrial Revolution.
Eliminates ingot casting and primary rolling steps
Improved metal quality (reduced segregation)
Energy efficient (reduced reheating needed)
High productivity (24/7 operation possible)
Limited to simple cross-sections (rounds, squares, rectangles)
Extremely high capital investment
Designed for mass production of standard shapes
Not suitable for finished parts
Steel billets for automotive manufacturing, aluminum slabs for aircraft plate, copper rounds for wire drawing
Shell molding creates thin, hard molds from resin-bonded sand, offering improved accuracy and surface finish over conventional sand casting.
Better dimensional accuracy than sand casting (±0.010")
Smoother surfaces (125-250 microinches Ra)
Reduced machining requirements
Good for medium to high production volumes
Higher material costs (resin-coated sand)
Pattern must be heated (energy cost)
Size limited by pattern heating requirements
Not economical for very low volumes
Cylinder heads, connecting rods, gear housings, small to medium production runs
Lost-foam casting uses expendable polystyrene foam patterns that vaporize when molten metal contacts them, eliminating pattern removal steps.
Complex geometries without cores or slides
No draft angles required
Eliminates parting lines
Reduced cleaning and finishing
Pattern is destroyed (single-use)
Foam pattern production costs
Potential for carbon pickup in steel castings
Requires effective venting for foam vapors
Automotive engine blocks, cylinder heads, complex artistic castings
High-pressure die casting injects molten metal at extreme pressures (10,000-25,000 PSI), achieving the fastest production rates and tightest tolerances in metal casting.
Fastest production rates (up to 1000+ parts/hour)
Thinnest walls possible (0.020" minimum for aluminum)
Exceptional dimensional consistency
Minimal porosity with proper process control
Highest tooling costs ($50,000-$500,000+ per die)
Limited to low melting point non-ferrous metals
Requires significant capital investment
Porosity challenges in thick sections
Automotive transmission cases, smartphone housings, laptop frames, engine components
Centrifugal casting uses rotational forces to distribute molten metal in cylindrical molds, producing dense, defect-free tubular parts.
Superior metal density and mechanical properties
Impurities concentrated in machined-away inner surface
No gating system required (reduced material waste)
Excellent for pipes, tubes, and cylindrical shapes
Limited to rotationally symmetrical parts
Inside diameter requires machining for accuracy
Equipment costs moderate to high
Outside diameter surface quality superior to inside
Pipe and tube manufacturing, cylinder liners, bearing races, flywheel rings
Permanent mold casting uses reusable metal molds (typically cast iron or steel) for gravity-fed or low-pressure metal flow, achieving quality between sand and die casting.
Better mechanical properties than sand casting
Good surface finish (125-250 microinches Ra)
Dimensional accuracy superior to sand casting
Cost-effective for medium to high production (1,000-100,000 units)
Moderate tooling costs ($5,000-$50,000)
Limited to aluminum, magnesium, copper alloys
Complex internal features require expendable cores
Thermal fatigue limits mold life (10,000-100,000+ cycles)
Automotive pistons, cylinder heads, gear blanks, cooking utensils
Vacuum casting removes air and gases from the mold cavity during metal pouring, significantly reducing porosity and improving casting quality.
Minimal porosity (critical for aerospace applications)
Reduced oxidation and inclusions
Improved mechanical properties
Enables thinner walls and complex geometries
Higher equipment costs
Slower production rates
Requires porous mold materials or effective venting
Process complexity demands skilled operators
Aerospace turbine blades, medical implants, high-performance automotive components
Low-pressure casting uses controlled gas pressure (3-15 PSI) to push molten metal upward into molds positioned above the furnace, filling cavities from bottom to top.
Excellent metal yield (minimal gating waste)
Reduced turbulence minimizes defects
Good mechanical properties (directional solidification)
Lower equipment costs than high-pressure die casting
Slower cycles than high-pressure die casting
Limited to aluminum and magnesium alloys
Furnace positioning constraints
Part geometry must allow bottom-up filling
Automotive wheels, engine components, structural aerospace parts
Squeeze die casting (liquid metal forging) combines casting and forging by applying high pressure to solidifying metal, producing near-forged properties in cast parts.
Superior mechanical properties (tensile strength 20-30% higher)
Minimal porosity
Fine grain structure
Reduced machining (near-net-shape)
High equipment costs
Slower cycles than conventional die casting
Die design complexity
Limited to non-ferrous metals
Automotive suspension components, aircraft landing gear parts, high-stress structural components
Plaster casting uses plaster-based molds for non-ferrous metals, achieving smooth surfaces and fine details impossible with sand.
Excellent surface finish (32-125 microinches Ra)
Fine detail reproduction
Smooth surfaces reduce finishing costs
Good dimensional accuracy
Drying time extends lead times
Limited to aluminum, copper, zinc (no ferrous metals)
Molds are single-use
Maximum casting temperature ~2,200°F
Artistic castings, prototypes, dental and medical components, decorative hardware
Selecting the optimal casting process depends on multiple factors:
Prototype/Low (<100): Sand, plaster, investment
Medium (100-10,000): Shell molding, permanent mold, gravity die
High (10,000+): Die casting, high-pressure die casting
Small (<1 lb): Die casting, investment casting
Medium (1-100 lbs): Most processes applicable
Large (>100 lbs): Sand casting, continuous casting
Ferrous metals: Sand, investment, shell molding
Non-ferrous metals: All processes applicable
High-temperature alloys: Investment, vacuum casting
High precision (±0.001-0.005"): Investment, die casting
Medium (±0.010-0.030"): Shell molding, permanent mold
Standard (±0.030"+): Sand casting
Smooth (32-125 microinches Ra): Investment, plaster, die casting
Medium (125-250 microinches Ra): Shell molding, permanent mold
Rough (250-500 microinches Ra): Sand casting
Low tooling investment: Sand, plaster
Medium investment: Shell molding, permanent mold
High investment: Die casting, squeeze casting
Sand casting remains the most widely used casting process globally, accounting for approximately 60-70% of all metal castings by tonnage. Its versatility, low tooling costs, and ability to produce parts from ounces to hundreds of tons make it indispensable across industries. However, die casting dominates high-volume production of smaller non-ferrous parts, particularly in automotive and consumer electronics.
Yes, metal casting encompasses both ferrous metals (iron, carbon steel, stainless steel) and non-ferrous metals (aluminum, copper, zinc, magnesium, titanium). Ferrous metals dominate tonnage production, while non-ferrous metals excel in applications requiring corrosion resistance, light weight, or thermal conductivity.
| Metal Type | Common Alloys | Typical Processes |
|---|---|---|
| Ferrous | Carbon steel, stainless steel, ductile iron | Sand, investment, shell molding |
| Aluminum | A356, A380, 319, 6061 | Die casting, sand, permanent mold |
| Copper | Bronze, brass | Sand, investment, centrifugal |
| Zinc | Zamak 3, Zamak 5, ZA-8 | Die casting (hot chamber) |
| Magnesium | AZ91D, AM60B | Die casting, permanent mold |
| Titanium | Ti-6Al-4V, commercially pure | Investment, vacuum casting |
Polyethylene and other plastics are not cast using metal casting processes. However, plastics utilize injection molding—a process conceptually similar to die casting where molten plastic is injected into molds under pressure. The fundamental difference lies in material properties and processing temperatures.
Everyday objects produced via casting include:
Automotive: Engine blocks, transmission housings, wheels, suspension components
Household: Faucets, door handles, cookware, plumbing fixtures
Industrial: Pump housings, valve bodies, machine tool components
Aerospace: Turbine blades, structural airframe parts, landing gear
While both processes fill molds with liquid material, key differences exist:
| Factor | Casting | Injection Molding |
|---|---|---|
| Material | Metals (melting points 1,000-3,000°F) | Plastics/polymers (processing temps 300-600°F) |
| Pressure | Gravity to 25,000 PSI (process-dependent) | 10,000-30,000 PSI (consistent) |
| Mold Material | Sand, plaster, ceramic, steel | Hardened steel, aluminum |
| Cycle Times | Minutes to hours (material/process-dependent) | Seconds to minutes |
| Material Properties | Superior strength, temperature resistance | Lower density, design flexibility |
The 14 types of casting processes offer manufacturers diverse options for producing metal parts ranging from prototype quantities to millions of units annually. Sand casting's versatility and low tooling costs make it ideal for large parts and low volumes, while die casting delivers exceptional accuracy and production rates for smaller non-ferrous components. Investment casting excels where complex geometries and superior surface finish justify higher costs, and specialized processes like centrifugal, vacuum, and squeeze casting address specific performance requirements.
Selecting the optimal casting process requires balancing production volume, part complexity, material requirements, dimensional tolerances, and budget constraints. Understanding each process's capabilities and limitations enables engineers to specify manufacturing methods that optimize quality, cost, and delivery for their specific applications.
The 14 main casting types include sand casting, die casting, investment casting, gravity die casting, continuous casting, shell molding, lost-foam casting, high-pressure die casting, centrifugal casting, permanent mold casting, vacuum casting, low-pressure casting, squeeze die casting, and plaster casting. Each process offers distinct advantages for specific applications, materials, and production volumes.
Sand casting uses expendable sand molds with low tooling costs, suitable for all metals and large parts but with rougher finishes. Die casting injects molten metal under high pressure into steel molds, achieving superior accuracy and surface finish but limited to non-ferrous metals with higher tooling investment. Sand casting suits low to medium volumes; die casting optimizes high-volume production.
Common casting defects include porosity (gas trapped during solidification), shrinkage cavities (insufficient metal feed during cooling), cold shuts (incomplete fusion of metal streams), hot tears (cracks from thermal stress), sand inclusions (mold material trapped in casting), and misruns (incomplete cavity filling). Proper gating design, mold venting, and process control minimize these issues.
Casting accommodates ferrous metals (carbon steel, stainless steel, cast iron), non-ferrous metals (aluminum, copper, zinc, magnesium, titanium), and specialized alloys (Inconel, Hastelloy, bronze, brass). Process selection depends on melting point, reactivity, and mechanical property requirements. Some processes specialize in specific material families.
Consider production volume (prototype vs. high-volume), part size and weight, material requirements (ferrous vs. non-ferrous), dimensional accuracy needs, surface finish requirements, and budget constraints. Sand casting suits low volumes and large parts; die casting optimizes high volumes of small to medium non-ferrous parts; investment casting excels for complex geometries requiring tight tolerances.
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