After the sand is scparated from the casting (this is referred to as shakeout in
ID: 326454 • Letter: A
Question
After the sand is scparated from the casting (this is referred to as shakeout in the schematic). it is screened to remove contaminants and stored. The sand must be at ambient tempcrature before it can be used to form new molds. This is accomplished at ABC by keeping the sand in storage ovemight before recycling. Consoquently, if mostly recycled sand is to be used, the molder's hopper must be able to hold enough sand for a full day's mold forming. 5. (20 pts) Read the following problem description for a foundry and answer the questions conceming it. Founding, or casting, is the process of forming metal objects by pouring molten metal into molds, and dates back to before 4000 B.C. Today, casting accounts for about 1/5 of all ferrous production annually and is also used extensively with a variety of nonferrous metals. The most common type of casting, and the predominant type at ABC,is sand casting. In sand casting, the mold is made by packing sand around a patterm. Once the pattern is removed, a cavity remains that is filled with molten metal. Interior surfaces of castings are formed by placing preformed sand cores into the mold cavity. The void between the core and the mold surface formed by the pattern imprint is what eventually becomes the casting. Quite complex castings can be created in this way. After the metal has solidified, the casting is separated from the molding sand and the sand is recycled. The casting is then sent to a clcaning station for the removal of any remaining sand, scale, and excess metal. a. Is material handling a problem with high, moderate, or low significance for ABC? Justify your answer. What materials need to be handled and moved in this system? What are some of the likely material handling objectives in this setting? What type of material handling equipment and system design would you recommend? Why? How would you analyze your design prior to implementation? b. c. d. The final quality of a casting depends critically on the proper conditioning of the molding sand. Various binders and additives, including clay and water, are added in a mixer. Coarse sand agglomerates are broken up in an acrator, so that the particle size is uniform. The objective of this conditioning is to have a sand that has adequate strength and plasticity for making and driven off by the heat of the molten metal, to resist crosion; and does not become so hard when heated that it is hard to remove from the casting. e. handling the mold; maintain s sufficient strength, when the moisture is Up to five pounds of sand is prepared and handled for every pound of metal poured in a foundry. Clearly, the handling of sand is a large part of operating a foundry. A timely supply of properly conditioned sand to the molder's hopper is critical to a foundry's efficient operation. Once in the molder's hopper, the molder takes sand as necessary to form the molds. A schematic diagram of the sand handling system at ABC is shown in B- New and Sytem slorage Sand Molder Mold Metal Screenin Core butts assorted waste Figure 1. Schematic diagram of sand handling processExplanation / Answer
a) Material handling is a problem with high significance for ABC because the final quality of the casting depends on the proper conditioning of the molding sand by passing it through a mixer and aereator before passing it to the Molders hopper which requires adequate quantities of conditioned sand to be available in it at all times, as the formation of the mold depends on it. Hence, we can say handling of the sand is an important part of operating a foundry.
b)The molding sand is formed by mixing together clay, water, binders and additives in a mixer. this is then passed through an aereator to break up coarse aggregates and obtain uniform particle size. Molten metal has to be poured into the mold once it is ready.
c) Likely material handling objectives would be quality control of sand as end product is entirely dependant for quality on the molding sand and also ensuring adequate supply of perfectly processed sand, Another requirement would be ensuring proper mode of collection and purification of recyclable sand and storage under optimum conditions to avoid excess reprocessing and ensure quality is not effected.
d) I would recommend a material handling equipment which is advanced in technology and allows for auto mixing of components to get the perfect molding sand as the quality of this is the backbone of the business. An automated system whereby the ingredients are fed through different slots into separate containers and the mechanised system decides the input quantity and processing. It should provide for the used sand to be input into a recycle container for different processing of removing contaminants and storing at required temperature before it is moved back into the fresh sand bin. Once the mold is perfectly ready the mechanism pours molten metal into it and treats for hardening and shakeout of the mold finally and recycling of the sand.
e) I would analyse the time duration for each process and the holding capacity of the Molders hopper as these are important considerations for the smooth flow of the entire operation from start to end. The time duration for processing the sand in mixer and aereator is crucial factor effecting quantity of ready molding sand available in the Hopper. I would like to minimise the risk of facing a situation where the hopper is without sand by having a hopper with enough capacity to meet a days requirement and also have a system in place whereby in case the Hopper reaches 30% full capacity an indicator light comes on so adequate action can be taken. The entire mechanism should be so controlled that the Hopper is always atleast half full.