Taking the most widely used sand casting as an example, the preparation of the casting mold in the coated sand core shooting process includes the preparation of the molding material and the two tasks of modeling and core making.
Modeling materials: all kinds of raw materials used for modeling and core making in sand casting, such as foundry raw sand, molding sand binder and other auxiliary materials, as well as molding sand, core sand, paint, etc. made from them, are collectively called molding materials.
The task of preparing molding materials is to select suitable raw sand, binder and auxiliary materials according to the requirements of castings and the nature of metals, and then mix them into molding sand and core sand with certain properties according to a certain ratio. Commonly used sand mixing equipment includes roller-type sand mixer, counter-flow sand mixer and continuous sand mixer. The latter is specially designed for mixing chemical self-hardening sand, with continuous mixing and high sand mixing speed.
Molding and core making: Moulding and core making are carried out on the basis of determining the molding method and preparing the molding materials according to the requirements of the casting process. The accuracy of castings and the economic effect of the entire production process are mainly determined by this process. In many modern casting workshops, modeling and core-making have been mechanized or automated.
Commonly used sand molding core making types of equipment include high, medium and low-pressure molding machines, air impact molding machines, boxless injection molding machines, cold-core box core making machines and hot core box core making machines, and coated sand core making machines.
The manufacturing method of the sand core is selected according to the sand core size, shape, production batch and specific production conditions. In production, it can be divided into manual core making and machine core making. Manual core making can be divided into core box core making and scraper core making.
Machine core making can be divided into core making outside the box, core making inside the box, and core making without curing. The core curing in the box also includes a hot core box method, a coated sand method, a cold core box method, and a self-hardening sand method.
The core making of the hot core box in the coated sand core shooting process is the core sand prepared with the thermosetting resin binder and the catalyst, which is injected into the core box heated to a certain temperature and is taken out after the sand core is hardened. The sand core with a smooth surface, precise size and high strength is obtained. It has high productivity, is easy to clean, does not need additional baking equipment for sand core, and is easy to realize the mechanization of core making, but it will produce a pungent odor during core making.
The application range of thermal core and core making is wide, and it can be used in batches, mass production, small and simple or more complex sand cores. To use the core box method to make cores, a hot core box core shooting machine must be used for the operation.
The core made of film-coated sand is the core sand using thermoplastic solid phenolic resin as the binder and urotropine as the curing agent, blown into the heated core box to maintain a certain crust time, after the thin shell is formed, the excess core sand is swayed and poured into the sand storage hopper to form a hollow thin shell sand core. The core sand used is called coated sand, so this core making method is called coated sand.
Film-coated sand in the coated sand core shooting process can be used not only to make cores but also to make shells. Because of its good shape, the surface of the sand core is dense, the strength of the sand core is high, and it is also widely used to manufacture complex thin-walled thermal cores (For example, water jacket sand core and air passage sand core of cylinder head casting). The coated sand core can be used in batches, mass production of small and medium-sized simple or complex sand cores.
The equipment that uses coated sand to make core is a coated sand core shooter. How to choose the appropriate coated sand core shooting machine according to the coated sand core shooting process depends on the size of the user’s own product mold.
Film-coated sand core shooting machines and hot core box core shooting machines are the most common and ideal use of casting equipment in modern casting enterprises, they bring more production benefits and profits to enterprises. The advantages of film-coated sand core shooter and hot core box core shooting machine are high core production rate, uniform compactness and good quality of sand core. Suitable for batch and mass production foundry manufacturers.
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