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Glossary

Aerospace Quality: Our precision parts – and the processes behind them – are built to meet aviation industry specifications and standards. At the same time, all of our customers benefit from the processes and practices designed to address the aerospace universe.

Burnout: As part of the casting process, the mold is subjected to heat ranging from 1600°F to 2000°F to remove the last traces of pattern materials, harden and strengthen the shell, and provide a hot cavity to receive molten metal. This crucial step ensures consistency in finish and accuracy.

Ceramic Shell: Part clusters are repeatedly dipped in a ceramic slurry, followed by a coating of fine ceramic sand. Once dry, the process is repeated multiple times, using progressively coarser grades of ceramic materials to build up shell that’s dimensionally stable under intense heat of molten metal.

Cluster or “Tree:” Part of the investment casting assembly process, patterns are mounted on one or more runners and attached to the pouring cup. Patterns, runner and pouring cups form the cluster or “tree” needed to create the ceramic mold.

Creep Resistance: The deformation that occurs over time when a component is subject to constant stress (e.g., high temperatures in the case of metals). 

Dewaxing: During the investment casting process, the coated cluster is placed in a high-temperature enclosure, where steam heat removes all wax. What remains is a ceramic shell with cavities of the desired casting shape with passages leading to them.

Ductility: The amount of deformation that a part can withstand without failure or fracture. See also Tensile Testing.

Elasticity/Stiffness: A type of mechanical property testing that measures the deformity of a part both before and after stress is applied. This ratio of stress (load) to strain (elongation) is known as stiffness. If a part encounters so much stress that it can no longer return to its original size, it can lose integrity, leading to material fatigue and even failure. See also Tensile Testing.

Elongation: See Elasticity/Stiffness and Tensile Testing.

Fatigue Strength and Endurance Limit: The most common form of mechanical breakdown in the production of parts, the repeated, cyclical application of stress can result in fatigue failure. The endurance limit occurs when a component reaches zero-failure regardless of the magnitude of stress and the number of cycles.

Finishing: Once the investment casting process is complete, the parts are ready for subsequent operations, such as inspection (visual, liquid penetrant, magnetic particle, x-ray) and machining. Machining can include milling, turning, drilling and grinding.

Functional Counter GravityTM: DP Cast uses a proprietary fill-control system known as Functional Counter GravityTM (FCG)to produce complex investment castings of various geometries. A disciplined application of FCG has led to excellent results in a variety of safety-critical parts. Click here for more information

Hardness: Important for any application requiring wear-resistance, hardness measures a part’s resistance to abrasion, deformation, scratching or to indentation by another hard body.

Investment Casting: Investment casting is an industrial process based on (and also called) lost-wax process, one of the oldest known metal-forming techniques, dating back thousands of years to ancient civilizations. The term refers to the ceramic materials used to create a hollow shell into which molten metal is “invested” (poured) to make the castings. Click here for more details on the process »

Load: See Elasticity/Stiffness and Tensile Testing.

Lost Wax Process: “Lost wax” is another term for investment casting. The process dates back thousands of years in regions from Mexico to Mesopotamia, Indian to Africa. Its earliest use was for intricate idols, sculpture, ornaments and jewelry, using natural beeswax for patterns, clay for the moulds and manually-operated bellows for stoking furnaces.

Liquid Penetrant Inspection (LPI): Also known as Dye Penetrant Inspection (DPI), LPI is one component of the Non-Destructive Testing process. In order to locate any surface-breaking defects in its castings, our technicians will look for surface porosity defects, leaks and cracks that could end up being very costly if left undetected.

Magnetic Particle Inspection (MPI): MPI is another Non-Destructive Testing process for detecting surface and near-surface flaws and inconsistencies. During the process, a magnetic field is applied outside of or through the part. If the material is sound, most of the magnetic flux is concentrated below the surface. If a defect is present, such that it interacts with the magnetic field, the flux is distorted locally and “leaks” from the surface of the part to the region of the flaw. Fine magnetic particles, applied to the area in question, are attracted to the flux leakage, creating a visible indication of the flaw.

Material Control at Source (MCS): DP Cast is qualified as an MCS provider for select clients. This certification authorizes us to operate under a client’s system with regard to testing and control of specified materials and processes, and ship direct to the client’s end customer. This results in greater efficiencies and significantly shorter lead times.

NAS-410 Certification: The National Aerospace Standard - 410 (NAS-410) represents the minimum qualification for inspectors who perform Non-Destructive Testing (NDT), a mandatory requirement in the aerospace and defense industries. Each NDT method requires its own certification and there are different levels of certification within each, the highest being Level III.

Near Net Shape: Near net shape is an industrial manufacturing technique, wherein the initial production of a part is very close to the final (net) shape, reducing the need for traditional finishing, such as machining or grinding which, in many cases, saves both time and money.

Non-Destructive Testing (NDT) at Source: NDT at source refers to the in-house utilization of a variety of testing methods that employ techniques and procedures to evaluate and determine the condition or integrity of materials such as metals, composites, plastics, etc. without damaging them. Methods include radiography/X-ray analysis, Liquid Penetrant Inspection (LPI), Magnetic Particle Inspection (MPI) and spectroanalysis.

Spectroanalysis: Part of the quality assurance process, spectroanalysis involves the use of a spectrometer to analyze alloy properties. When used in conjunction with investment casting, it can ensure and improve the appropriate material composition of a part. It also allows us to alloy materials to specific requirements and/or desired metallurgical properties.

Tensile Testing: A methodology used to determine the mechanical properties of materials. When a test specimen is axially loaded, the load is increased at a uniform rate, causing the sample to elongate and, eventually, fracture. Both the load and the elongation are recorded and plotted based on the diagram below, where:

stress = load/original cross-sectional area
strain = increase in length under load/original length

Other mechanical property specifications, such as Yield, Ultimate Tensile Strength (UTS), Ductility and Elasticity/Stiffness, can be determined from this plot.

Tensile Testing Image
Source: WMG, International Manufacturing Centre, University of Warwick.

Toughness: The force required to cause a fracture in a part. Higher UTS and ductility result in higher toughness and a stronger, more resistant part.

Ultimate Tensile Strength (UTS): A measure used in mechanical property testing to specify the maximum amount of stress a part can withstand before failure. See also Tensile Testing.

Wax Pattern: Required for each casting, a disposable pattern is created by injecting wax into a metal die. These patterns have the exact specifications of the finished part, but are made slightly larger, to compensate for volumetric shrinkage during production or the solidification of metal in the ceramic mold.

Yield (or Proof Strength): A form of tensile testing that measures the stress required to produce a prescribed level of deformity (generally a 0.2% change in length). See also Tensile Testing.