Search Results for pattern production

The Replicast process is developed to overcome the formation of lustrous carbon defects and carbon pickup observed in conventional evaporative pattern casting processes. This article provides a discussion on the pattern production, process capabilities, advantages, and limitations of Replicast process.

This article discusses the types of patterns used for a specific application such as loose patterns, match plate patterns, cope and drag patterns, and special patterns. It describes the principles of the patternmaking techniques used to make expendable molds and for metal casting processes such as die casting and permanent mold casting. The article reviews the pattern features and mold production considerations used in the pattern design, namely, parting line considerations, addition of gates and risers, core prints, and locating points. It examines the pattern allowances for ensuring a dimensionally correct final pattern. A variety of materials and advanced composite materials used in the manufacture of patterns are discussed. The article evaluates the factors influencing the selection of type of patterns for specific castings.

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.

This article suggests procedures to increase the availability and function of patterns and tooling. It discusses the common expected failure mechanisms, such as erosion and fatigue, for dies and patterns. A successful maintenance program requires good record keeping for each tool. The article lists information required for the maintenance tooling record and preventive maintenance (PM) items from the North American Die Casting Association's publication E501. It concludes with information on objectives for proper storage of tools and patterns. The objectives are preventing tool degradation, safe workplace, easy location, proximity, and cataloging and tracking.

This article describes processes and equipment that are used to produce composite tubular parts. The processes include sheeting, pattern cutting, tube rolling, shrink tape debulking, and finishing. The article provides a discussion on materials that are most suitable for tube rolling: preimpregnated materials and unidirectional tapes. The article also discusses wrapping techniques of cylindrical and tapered tubes, such as convolute and spiral wrapping.

Depending on the size and application, castings manufactured with the expendable mold process and with expendable patterns increase the tolerance from 1.5 to 3.5 times that of the permanent pattern methods. This article reviews the two major expendable pattern methods, such as lost foam and investment casting. It discusses the Replicast casting process that involves patternmaking with polystyrene and a ceramic shell mold. The article contains a table that summarizes the differences in the steps of casting a part between the permanent pattern and expendable pattern methods.

This article describes the four basic steps of the purchasing process of cast components. These steps include defining requirements and developing a purchasing plan; requesting and evaluating bids from potential sources; selecting a source and negotiating contract terms; and carrying out the contract and pursuing continuous improvement. It provides guidance on purchasing cast components and explains specific issues and approaches that have proven to be useful in purchasing castings. The article presents a list of the most significant considerations when attempting to determine the overall cost and design requirements of a metal casting.

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.

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.

This article discusses the sequence of operations for producing a foam pattern for casting. It provides information on expandable polystyrene, the most preferred material for manufacturing lost foam patterns. The article then describes the major functions of pattern molding and assembly. The types and application methods of various lost foam coatings are explained. The article also describes the investment of the foam pattern in a sand system. It concludes with a discussion on the advantages of lost foam casting and information on the formation and control of folds.

This article discusses slurry molding that encompasses two distinct processes: plaster molding and ceramic molding. Plaster mold casting is a specialized casting process used to produce nonferrous castings that have greater dimensional accuracy, smoother surfaces, and more finely reproduced detail. The article describes three generally recognized plaster mold processes, namely, conventional plaster mold casting, the Antioch process, and the foamed plaster process. Ceramic molding techniques are based on processes that employ permanent patterns and fine-grained zircon and calcined, high-alumina mullite slurries for molding. The Shaw process and the proprietary Unicast processes are also discussed.

Lost foam casting is a sand casting process in which the mold consists of an evaporative polystyrene foam pattern embedded in sand. It is especially well suited for making complex parts with convoluted features such as engine blocks, transmission cases, and cylinder heads. This article describes the lost foam casting process and its primary advantages, including the elimination of flash and parting lines, the relative ease of prototyping with foam, and the ability to incorporate multiple metals, whether in sections or layers, through sequential pours. It illustrates an entire process cycle from mold filling to fusion, cooling, and part ejection. The article also provides information on casting quality, discussing dimensional tolerances, fold defects, and porosity.

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 reviews the pattern materials used in investment casting, which can be loosely grouped into waxes and plastics. The patternmaking process, pattern tooling, and pattern and cluster assembly are described. The article also describes the manufacture of ceramic shell molds and cores, detailing the binders and other materials used, as well as the formulation and control of slurries. Methods for pattern removal, mold firing, melting, casting, postcasting treatment, and inspection are explained. After presenting design recommendations for investment castings, the article concludes with information on applications and special versions of the investment casting process.

Tooling and assembly methodologies for advanced composites have steadily improved as a result of advancements in materials, through the use of computer-aided design/computer-aided manufacturing technology, and through application of sophisticated design for manufacturing and assembly concepts. This article reviews techniques and technologies that are used to control the quality of tooling and assembly methods for composite components.