The investment casting process is characterized by a sequence of intricate steps, each involving specific materials, equipment, and parameters. Consequently, a specialized vocabulary has developed to describe these elements with precision.
- Alloy: A solid solution consisting of two or more chemical elements, at least one of which is a metal.
- Annealing: A heat treatment process involving heating a metal to a suitable temperature, holding it at that temperature, and then cooling it slowly, typically to induce softness, improve machinability, or relieve internal stresses.
- AQL (Acceptable Quality Level): A quality level established for inspection, often using statistical sampling, defining the maximum percent defective considered satisfactory as a process average.
- As Cast: The condition of a casting after solidification and removal from the mold, but before any secondary operations like heat treatment or machining.
- Autoclave: A pressurized vessel using steam and heat for Dewaxing ceramic shells.
- Binder: An agent in the ceramic Slurry (e.g., colloidal silica, ethyl silicate) that bonds refractory particles together to form a hardened shell.
- Blowhole: A relatively large, often rounded gas cavity within a casting, caused by trapped air or mold gases.
- Burn-on Sand: Sand or refractory material from the mold that has fused to the surface of the casting and is difficult to remove.
- Burnout: The process of heating an invested mold in a furnace to eliminate all traces of the pattern material (wax or plastic) and to cure the investment mold.
- CAD (Computer-Aided Design): Software used for creating 2D/3D geometric models of parts and tooling.
- CAM (Computer-Aided Manufacturing): Software used for optimizing and controlling manufacturing processes.
- Casting: The process of pouring molten metal into a mold to form a solid shape; also refers to the solidified metal part itself.
- Ceramic Core: A pre-formed ceramic shape placed in a die before wax injection to create internal features in a casting; it remains through shelling and is removed after casting.
- Ceramic Shell / Mold: The hardened, multi-layered refractory ceramic structure formed around the wax pattern, which becomes the mold once the wax is removed.
- Charge: A given weight and composition of metal introduced into a furnace for melting.
- Chill: A metal insert placed in a mold to promote localized rapid cooling and directional solidification (more common in sand casting but principle applies).
- Cleaning: The process of removing runners, risers, flash, surplus metal, and adherent mold material from a casting.
- Cluster (of parts): An assembly of multiple Wax Patterns on a common runner system, also known as a Tree .
- Cold Shut / Cold Lap: A surface imperfection where two streams of molten metal fail to fuse properly in the mold cavity.
- Cope: The top half of a horizontally parted mold (primarily a sand casting term, less relevant to typical investment casting shells).
- Core: A pre-formed insert, made of sand, ceramic, or soluble wax, used to create internal cavities or features in a casting.
- Corebox: A tool used to produce Cores .
- Cure: To harden, typically referring to the ceramic shell through drying and firing.
- Cutoff / Degating: Separating individual castings from the central Sprue , Runners , and Gates of the metal tree.
- Dewaxing / Wax Removal: The process of melting and removing the wax pattern from the hardened ceramic shell to create the mold cavity.
- DFM (Design For Manufacturing/Manufacturability): A design approach considering manufacturing process capabilities to optimize for ease of manufacturing, quality, and cost.
- Die: A metal form or mold used to produce Wax Patterns in investment casting; also known as Master Die or Wax Injection Mold .
- Dimensional Inspection: Measuring a casting to ensure its dimensions are within specified tolerances .
- Dowel: A pin used in parted patterns or dies to ensure correct alignment.
- Draft Angle / Taper: Taper on the vertical sides of a pattern to permit easy removal from a mold. Investment casting often allows for zero or minimal draft.
- Drag: The bottom half of a horizontally parted mold (primarily a sand casting term).
- Drying: The process of allowing coated layers of slurry and stucco to harden by evaporation of the liquid carrier.
- Dye Penetrant Inspection (DPI): An NDT method to detect surface-breaking defects using a colored or fluorescent dye.
- Ejector Pins: Movable pins in pattern dies that help remove wax patterns from the die.
- Facing Sand: In sand casting, the sand layer surrounding the pattern that contacts molten metal. The Prime Coat serves a similar function in investment casting.
- Ferrous Metals: Alloys predominantly made up of iron (e.g., steels, stainless steels).
- Finish Allowance: Amount of stock left on a casting surface for subsequent machining (minimized in investment casting).
- Finishing: Secondary operations (grinding, machining, polishing) to achieve final dimensions, surface quality, and properties.
- Firing / Preheating (of Mold): High-temperature heating of the dewaxed ceramic shell to cure it, burn off residues, and preheat it for casting.
- Flask: A rigid frame used to hold molding material; can be used in block mold investment casting.
- Flash Fire Dewaxing: A method of rapidly heating a ceramic shell to melt/vaporize the wax pattern.
- Fluidized Bed: Equipment for applying Stucco by immersing a wet pattern into a bed of ceramic particles aerated to behave like a fluid.
- Foundry Returns: Metal (gates, sprues, risers, scrapped castings) of known composition returned to the furnace for remelting.
- Gas Porosity: Voids in a casting caused by trapped gases.
- Gate / Ingate: The specific point(s) where molten metal enters the actual mold cavity for the part.
- Gating System: The network of channels (sprue, runners, gates) that directs molten metal into the mold cavity.
- Green Sand: Moist clay-bonded molding sand (a sand casting term).
- Grinding: An abrasive machining process used to remove excess material or improve surface finish.
- Hardness Testing: A mechanical test to measure a material’s resistance to indentation.
- Heat Treatment: Controlled heating and cooling cycles applied to castings to modify their metallurgical structure and mechanical properties.
- Hot Isostatic Pressing (HIP): A process applying simultaneous high temperature and high inert gas pressure to a casting to reduce internal porosity and improve density and mechanical properties.
- Hot Tear / Shrinkage Crack: An irregular fracture in a casting from stresses during solidification when metal contraction is restricted.
- Inclusion: Non-metallic particles (slag, refractory, sand) trapped within a casting.
- Injection Molding (for Patterns): Process of injecting molten wax into a Master Die to form a Wax Pattern .
- Investment / Investing: The process of repeatedly dipping a wax pattern assembly into Slurry , stuccoing it, and drying it to build a laminated ceramic shell. Also refers to the shell itself.
- Investment Casting: A manufacturing process where a wax pattern is coated with refractory ceramic material; the wax is melted out, and molten metal is poured into the resulting cavity. Also known as Lost-Wax Casting or Precision Casting .
- Investment Material: The ceramic material mixture (refractory + binder + modifiers) used to form the mold around a pattern.
- Knockout / Shakeout / Shell Removal: Breaking away and removing the ceramic shell from the solidified metal casting.
- Ladle: A refractory-lined vessel for transferring molten metal.
- Lost-Wax Casting: An alternative name for Investment Casting , referring to the melting out of the wax pattern.
- Machining: Material removal processes (milling, turning, etc.) to achieve precise dimensions or features.
- Master Die / Wax Injection Mold / Tooling: A precision mold, typically metal, used to produce multiple identical Wax Patterns .
- Master Pattern: An object from which a die can be made; generally a model of the part with shrinkage allowances added (more relevant if die is not directly machined from CAD).
- Mechanical Properties: Properties of a material that describe its elastic and inelastic behavior when force is applied (e.g., strength, ductility, hardness).
- Melt: Molten metal ready for casting.
- Melting Furnace: Equipment used to melt casting alloys.
- Metal Penetration: Molten metal infiltrates pores or cracks in the ceramic mold, causing a rough surface.
- Metal Yield: The ratio of the finished casting’s weight to the total weight of metal poured.
- Misrun / Non-fill: A defect where molten metal fails to completely fill the mold cavity.
- Mold: The cavity or form into which molten metal is poured to create a casting. In investment casting, this is the Ceramic Shell .
- Mold Cavity: The impression in a mold, created by the pattern, which is filled with molten metal.
- Molten Metal: Metal heated above its melting point to a liquid state.
- Near-Net Shape: A casting produced very close to the final required dimensions, minimizing subsequent machining.
- Net Shape: A casting produced to exact final dimensions, requiring no subsequent machining.
- Nickel-Based Alloys (Superalloys): High-performance alloys (e.g., Inconel) used for high-temperature strength and corrosion resistance.
- Non-Destructive Testing (NDT): Inspection methods that evaluate casting integrity without damaging the part (e.g., X-ray, DPI, MPI, UT).
- Non-ferrous Metals: Alloys not predominantly made up of iron (e.g., aluminum, copper, nickel alloys).
- Pattern: A replica of the final product to be made, typically from wax or thermoplastic in investment casting.
- Patternmaker’s Shrinkage: Shrinkage allowance made on patterns to compensate for metal contraction during cooling.
- Permeability: The property of a mold material to allow gases to escape during pouring.
- Pinhole: Small gas Porosity in a casting.
- Polishing: A finishing process to create a smooth, reflective surface.
- Porosity: Small voids, holes, or cavities within a casting, often from trapped gases or shrinkage.
- Pouring / Casting (Operation): The act of introducing molten metal into the prepared mold cavity.
- Pouring Cup / Basin: The funnel-shaped opening at the top of the mold where molten metal is introduced.
- Precision Casting: An alternative name for Investment Casting , highlighting its ability to produce parts with high accuracy and detail.
- Precipitation Hardening (Aging): A heat treatment process that strengthens alloys by precipitating fine particles within the metal matrix.
- Prime Coat (Face Coat): The first one or two layers of fine refractory slurry applied to the wax pattern, crucial for surface finish and detail.
- Rainfall Sander: Equipment for applying Stucco by raining particles onto a wet pattern.
- Rapid Prototyping: Technologies (e.g., 3D printing) used to quickly produce prototypes or patterns from CAD models.
- Refractory Material: Heat-resistant ceramic materials (e.g., silica, zircon, alumina) used to create the investment casting mold.
- Riser / Feeder: A reservoir of molten metal connected to the casting cavity to compensate for Shrinkage during solidification.
- Runner: A channel in the gating system that distributes molten metal from the sprue to the ingates.
- Sandblasting: An abrasive blasting process for cleaning surfaces or removing scale.
- Scrap: Waste metal produced during casting; also, reject castings or metal remelted.
- Shrinkage: The volumetric contraction of metal during cooling and solidification.
- Shrinkage Allowance: Oversizing of patterns and dies to compensate for metal Shrinkage .
- Shrinkage Cavity: A void in a casting resulting from uncompensated Shrinkage .
- Silica (Silicon Dioxide): A common refractory material (SiO2) used in investment casting slurries and stuccos.
- Slag: A non-metallic film or byproduct that forms on molten metal. If trapped in casting, it’s an Inclusion .
- Slurry: A liquid mixture of fine Refractory Material , a Binder , and other modifying agents, used to coat the wax pattern.
- Slurry Tank / Mixer: Equipment for holding and agitating ceramic Slurry .
- Solidification: The process by which molten metal cools and transitions from a liquid to a solid state.
- Solidification Modelling: Computerized simulation of the casting, filling, and solidification process to predict and prevent defects.
- Soluble Wax Core: A wax core used to form internal features in a pattern, later dissolved out before shelling.
- Solution Treatment: A heat treatment process involving heating an alloy to a suitable temperature to dissolve constituents, followed by rapid cooling.
- Spectrographic Analysis: Testing molten metal or castings to verify chemical composition.
- Sprue (Pattern Assembly / Downsprue): The central wax runner system to which patterns are attached to form a Tree ; also, the main vertical channel in the gating system through which metal descends.
- Stainless Steel Alloys: Ferrous alloys containing chromium (and often nickel) for corrosion resistance.
- Stucco / Stuccoing: Coarse ceramic sand or grit applied to a wet slurry-coated pattern to build shell thickness and strength; also the process of applying it.
- Superalloys: See Nickel-Based Alloys or Cobalt-Based Alloys; high-performance alloys for extreme conditions.
- Surface Finish: The texture and smoothness of a casting surface.
- Tensile Testing: A mechanical test measuring a material’s strength and ductility under tension.
- Test Bar: A standard specimen cast alongside production parts or from the same melt, used for Mechanical Property Testing .
- Titanium Alloys: Lightweight, high-strength, corrosion-resistant non-ferrous alloys.
- Tolerance: The permissible variation in a dimension of a part.
- Tree / Cluster: An assembly of Wax Patterns on a common runner system ( Sprue ) for simultaneous casting.
- Vent: A small channel in a mold to allow air and mold gases to escape as metal fills the cavity.
- Visual Inspection (VT): Examining a casting for surface defects by eye.
- Wax (Pattern Material): Specialized formulations used to create expendable patterns.
- Wax Injection Machine / Press: Equipment to melt and inject wax into a Wax Injection Mold .
- Wax Pattern: A sacrificial replica of the final part, typically made from wax.
- Zircon (Zirconium Silicate): A highly refractory material (ZrSiO4) often used in prime coats of ceramic shells.
