Rotational molding is a simple but unique process that has the capability of producing small to large hollow items with very uniform wall thicknesses. Providing an overview of the operating principles of rotational molding, this article discusses the key selection factors, including function and property requirements for resins and additives; size, shape, design, and cost of molded parts; equipment type and size; and the type of mold to be used. Commonly used molds include cast aluminum, fabricated sheet metal, nickel deposit, machined aluminum, silicone, fiberglass, and prototype molds.

Vertical centrifugal casting machines, installed below the ground level for maximum operator safety, are used for producing bushings and castings that are relatively large in diameter and short in length. This article discusses the mold design for different types of sand molds and permanent molds and their production considerations. It describes the speed of rotation, mold speeds curves, and pouring techniques that are considered in the operation of vertical centrifugal casting machines.

Resin transfer molding (RTM) and structural reaction injection molding (SRIM) are two similar processes that are well suited to the manufacture of large, complex, and high-performance structures. This article discusses the similarities and differences of RTM and SRIM processes and the unique design considerations with respect to the physical properties, geometry, surface quality, process economics, equipment, and tooling of a component that should be considered in choosing RTM or SRIM over other competing processes for fabricating reinforced components.

This article discusses classification of foundry processes based on the molding medium, such as sand molds, ceramic molds, and metallic molds. Sand molds can be briefly classified into two types: bonded sand molds, and unbonded sand molds. Bonded sand molds include green sand molds, dry sand molds, resin-bonded sand molds, and sodium silicate bonded sand. The article describes the casting processes that use these molds, including the no-bake process, cold box process, hot box process, the CO2 process, lost foam casting process and vacuum molding process. The casting processes that use ceramic molds include investment casting, and plaster casting. Metallic molds are used in permanent mold casting, die casting, semisolid casting, and centrifugal casting.

Green sand molding and chemically bonded sand molding are considered to be the most basic and widely used mold-making processes. This article describes the sand system formulation, preparation, mulling, mold fabrication, and handling of green sand molds. It lists the advantages and disadvantages of green sand molding. The article discusses the primary control parameters for the sand system formulation. It describes two basic types of green sand molds such as flask molds and flaskless molds. The article provides a discussion on molding problems including springback and expansion defects. It discusses a variety of sand reclamation systems, including wet washing/scrubbing and thermal-calcining/thermal-dry scrubbing combinations.

Shell molding is used for making production quantities of castings that range in weight from a few ounces to approximately 180 kg (400 lb), in both ferrous and nonferrous metals. This article lists the limitations or disadvantages of shell mold casting. It describes the two methods for preparation of resin-sand mixture for shell molding, namely, mixing resin and sand according to conventional dry mixing techniques, and coating the sand with resin. Shaping of shell molds and cores from resin sand mixtures is accomplished in machines. The article discusses the major steps in producing a mold or core and describes the problems most frequently encountered in shell-mold casting. The problems include mold cracking, soft molds, low hot tensile strength of molds, peelback, and mold shift. The article concludes with information on examples that provide some relative cost comparisons between shell molding and green sand molding.

Blow molding has emerged as a commercially viable process for manufacturing parts for nonpackaging/industrial markets. This article discusses the machinery required, processing methods, mold types, process parameters, part designs and material distribution of blow molding. It provides an outline of the parison programming system equipped with blow molders to control the parison thickness. The article describes factors that are usually considered to minimize material distribution problems, namely, design, material selection, process control, part performance, and cost.

Injection molding is a process of forcing or injecting a fluid plastic material into a closed mold. The process generally has the advantages of being more readily automated and of permitting finer part details. Injection-molding compounds are thermoplastic or thermosetting materials and their composites that are specifically formulated for the injection-molding process. This article discusses the injection molding process, which includes the two basic categories of thermoplastic and thermoset injection molding, and lists the common thermoplastic and thermoset molding compounds and applications. It also describes the operation of the different types of injection molding machines as well as mold design and process controls. The article also describes the selection of injection-moldable thermosets, and provides an overview of part performance, properties, blowing agents, and aesthetic concerns related to thermoplastic structural-foam injection molding.

Autoclave molding is a process used to impart a controlled heat and pressure cycle cure to a layup. This article describes the materials used for preparing a layup, including peel ply, separator, bleeder, barrier, breather, dam, and vacuum bag. It describes the major elements and functions of an autoclave system, including pressure vessel, gas stream heating and circulation sources, gas stream pressurizing systems, vacuum systems, control systems, and loading systems. The article includes information about modified autoclaves for specialized applications and safety practices in autoclave molding. It also describes the tooling configuration and type of tooling which includes aluminum and steel tooling, electroformed nickel tooling, graphite-epoxy tooling, and elastomeric tooling.

This article provides information on metals that can be cast in permanent molds. It discusses the manual and automatic operations, design guidelines, advantages, disadvantages, and applications of the casting. The article describes the number of factors considered when designing and building the molds. It examines the effect of mold design on mold life. The article outlines the primary purposes, procedure, and application of mold coatings. The variables that determine mold temperature and control measures associated with mold temperature are reviewed. The article explains the effect of short-term and long-term variables on the dimensional accuracy of permanent mold castings. It concludes with information on the factors of the surface finish on permanent mold castings.

Wet lay-up using hand or spray techniques is one of the simplest methods of combining a fiber reinforcement with a solidifying resin to form a composite structure. This article describes several wet lay-up processes - including contact molding, spray molding, vacuum bag molding, and autoclave molding - suited for making parts on open-faced molds using polyester and vinyl ester resins. The article also provides information on mechanically assisted lay-up which can be automated to alleviate some of the manual work.

Babbitting is a process by which relatively soft metals are bonded chemically or mechanically to a stronger shell or stiffener which supports the weight and torsion of a rotating, oscillating, or sliding shaft. This article focuses on workpiece preparation and babbitting methods. Prior to casting, the workpiece must be scrupulously prepared by various cleaning, fluxing, and tinning steps. Babbitting of bearing shells can be accomplished by three methods, namely, static babbitting, centrifugal casting, and metal spray babbitting.

A sliding bearing (plain bearing) is a machine element designed to transmit loads or reaction forces to a shaft that rotates relative to the bearing. This article explains the role of wear damage mechanisms in the design and selection of bearing materials, and its relationship with bearing material properties. Sliding bearings are commonly classified by terms that describe their application; they also are classified according to material construction, as single-metal, bimetal, or trimetal sliding bearings. The article further provides detailed tabular data on the designation and composition of the following types of bearing materials: tin-base alloys, lead-base alloys, copper-base alloys, and aluminum-base alloys. It also briefly discusses the following types of bearing materials: zinc-base alloys, silver-base alloys, gray cast irons, cemented carbides, and nonmetallic bearing materials.

This article describes the applications, advantages, and disadvantages of three centrifugal casting processes as well as the equipment used. The processes include true centrifugal casting (horizontal, vertical, or inclined) semicentrifugal (centrifugal mold) casting, and centrifuge mold (centrifugal die) casting. The article discusses the cooling, inoculation, fluxing, and extraction of casting. It reviews mold heating and coating techniques as well as various molds used for the centrifugal casting processes. The three most common defects observed in centrifugal castings are also discussed. The article concludes with information on the applications of centrifugal force in investment casting and combustion synthesis.

This article reviews the basic types of mold aggregates and bonding methods for expendable molds and coremaking. It provides an overview of mold media and the basic types of sands and their properties. The most significant clays used in green sand operations, such as bentonites, are discussed. The article describes the methods of sand bonding with inorganic compounds. It provides a description of resin-bonded sand systems, namely, no-bake binder systems, heat-cured binder systems, and cold box binder systems. The article concludes with a discussion on the media used for expendable molds, namely, ceramic shells and rammed graphite, for casting reactive metals such as titanium or zirconium.

This article provides a general introduction on casting processes and design. It discusses the process steps and methods of the main categories of shape casting methods, namely, expendable molds with permanent patterns, expendable molds with expendable patterns, and metal or permanent mold processes. The article lists general guidelines of geometry in casting design. It describes the factors, such as mold complexity and casting solidification, in casting design. The solidification of a casting can involve as many as three separate contractions as a result of cooling: liquid-liquid contraction, solid-solid contraction, and liquid-solid contraction. The article discusses the factors influencing the solidification sequence of simple shapes, such as T-sections, X-sections, and L-sections. It also provides an overview of geometric factors that influence heat transfer and transport phenomena. The article concludes with a description of the structure and properties of a casting.

Horizontal centrifugal casting is used to cast parts having an axis of revolution. This article discusses the operations of various horizontal casting machines, such as flanged shaft machine, horizontal roller-type machine, and double-face plate machine. It describes the types of molds, such as expendable molds and permanent molds, used for centrifugal casting. The article also discusses the steps in casting process, namely, pouring, solidification, and babbitting. It provides information on the applications of the horizontal centrifugal casting.

Thermoforming is a manufacturing process in which thermoplastic sheets are heated, softened, clamped onto a mold, and made to conform to the shape of the mold or forming tool. It is ideally suited to large-volume runs of small items. This article focuses on major phases of thermoforming, namely, sheet transportation, heating, forming/cooling, and trimming, and different thermoforming techniques: basic female forming; basic male forming; matched-mold thermoforming; plug-assist thermoforming; pressure bubble plug-assist vacuum thermoforming; vacuum snapback thermoforming; air-slip thermoforming; and trapped-sheet, contact heat, and pressure thermoforming. It concludes with a discussion on machines and the economic concerns of thermoforming.

The combination of high strength-to-weight ratio, excellent mechanical properties, and corrosion resistance makes titanium the best material choice for many critical applications. This article begins with a description of the historical perspective of titanium casting technology. It discusses the types of molding methods, such as rammed graphite molding and lost-wax investment molding. The article provides information on the casting design, melting, postcasting, and pouring practices. It describes the microstructure and mechanical properties of Ti-6AI-4V alloy. The article examines the product applications of titanium alloy castings. The tensile properties, standard industry specifications, and chemical compositions of various titanium alloy castings are tabulated.

This article reviews the pattern materials used in investment casting. It describes patternmaking process, pattern tooling, and pattern and cluster assembly. The article provides information on melting equipment, casting methods, and the inspection and testing of investment casted materials. It presents recommendations that which serve as a useful guide to the design of investment castings. The article tabulates the applications of the process and illustrates the Shellvest system for investment casting of small parts. It explains the manufacturing process of ceramic shell molds and cores. Binders and materials used for ceramic shell molds; slurry and cluster formulation; and pattern removal methods in the manufacturing process are summarized. The article discusses the coating and drying process of clusters and slurries.