Search Results for dry sand molding

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.

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.

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: flask molds and flaskless molds. The article provides a discussion on molding problems, including springback and expansion defects. It considers a variety of sand reclamation systems, including wet washing/scrubbing and thermal-calcining/thermal-dry scrubbing combinations.

No-bake sand molds are based on the curing of inorganic or organic binders with either gaseous catalysts or liquid catalysts. This article reviews the major aspects of no-bake sand bonding in terms of coremaking, molding methods, and sand processing. It discusses the points to be noted in handling sand-resin mixtures for no-bake molds or cones and lists some advantages of no-bake air-set cores and molds. The article describes the process procedures, advantages, and disadvantages of gas curing and air-setting hardening of sodium silicates. It examines the members of the air-setting organic binders, namely, furan no-bake resins, phenolic no-bake resins, and urethanes. The article provides an overview of gas-cured organic binders. It also illustrates the three commercial systems for sand reclamation: wet reclamation systems, dry reclamation systems, and thermal reclamation.

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.

This article describes the process and advantages of no-bond methods of vacuum molding and magnetic molding, with schematic illustrations. It also discusses the characteristics of plastic film and dimensional specifications of vacuum molding.

In many castings, functional requirements dictate that walls be uniform or nearly uniform in thickness. Many problems in producing castings having walls of uniform thickness are associated with the premature freezing of molten metal before all parts of the mold cavity have been filled. This article discusses the design problems and solutions of various castings, such as sand, shell mold, permanent mold, and investment castings, with illustrations.

Aggregate molding, or sand casting, is the gravity pouring of liquid metal into a mold that is made of a mixture molded against a permanent pattern. This article summarizes the most important materials in the process of sand casting of cast iron, including different types of molding aggregates, clays, water, and additives in green sand, chemically bonded organic resins, and inorganic binders in self-setting, thermosetting, and gas-triggered systems. It discusses three main types of reclamation systems: wet, dry, and thermal. The article concludes with a description of both nonpermanent and permanent mold processes.

Thin sections save weight and thus contribute to a more favorable strength-to-weight ratio. By requiring a smaller volume of metal, thin walls may also lower casting costs, particularly when an expensive alloy is being poured. This article discusses the design problems in thin-wall steel sand castings, thin-wall aluminum and magnesium castings, thin-wall permanent mold castings, and thin-wall investment castings, with schematic illustrations.

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: 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.

Aluminum casting alloys are the most versatile of all common foundry alloys and generally have the highest castability ratings. This article discusses the designation and classification of aluminum casting alloys based on their composition and the factors influencing alloy selection. Alloys discussed include rotor alloys, commercial duralumin alloys, premium casting alloys, piston and elevated-temperature alloys, general-purpose alloys, magnesium alloys, aluminum-zinc-magnesium alloys, and bearing alloys. Six basic types of aluminum alloys developed for casting include aluminum-copper, aluminum-copper-silicon, aluminum-silicon, aluminum-magnesium, aluminum-zinc-magnesium, and aluminum-tin. The article also describes the main casting processes for aluminum alloys, which include die casting, permanent mold casting, sand casting (green sand and dry sand), plaster casting, and investment casting. In addition, the article discusses factors affecting the mechanical and physical properties, microstructural features that affect mechanical properties, the effects of alloying, and major applications of aluminum casting alloys.

Cores are separate shapes of sand that are placed in the mold to provide castings with contours, cavities, and passages that are not otherwise practical or physically obtainable by the mold. This article describes the basic principles of coremaking and the types of core sands, binders, and additives used in coremaking. It discusses the curing of compacted cores by core baking and the hot box processes. The article provides an overview of the core coatings, assembling and core setting, coring of tortuous passages, and cores in permanent mold castings and investment castings. It also discusses the design considerations in coremaking to eliminate cores and compares coring with drilling.

Horizontal centrifugal casting is used to cast parts having an axis of revolution. This article discusses the operations of three types of horizontal casting machine: the flanged shaft machine, the horizontal roller-type machine, and the double-face plate machine. It provides information on expendable and permanent molds used for centrifugal casting. The parameters and operations of the horizontal centrifugal casting process, including pouring and solidification, as well as the applications are described.