Large castings of machine tools include machine tool bed, worktable, column, crossbeam, and gantry top connecting beam. The bed castings have good shock absorption properties. The melting point is relatively low, the fluidity is good, and the shrinkage rate is small.

Characteristics of castings

(1) Disappearing mold castings have good shock absorption properties. Due to the favorable lubrication and oil storage properties of graphite in cast iron. Similarly, due to the superior shock absorption properties of graphite compared to steel.

(2) Good process performance. Due to its high carbon content and eutectic composition, gray cast iron has a relatively low melting point, good flowability, and low shrinkage rate, making it suitable for casting complex or thin-walled castings. In addition, due to the tendency of graphite to form chips during cutting, the machinability of gray cast iron is superior to that of steel.

Advantages of large castings for machine tools

(1) Resin sand molds have good rigidity, and in the early stage of casting, it is possible to utilize the graphitization expansion, shrinkage, and porosity defects during the solidification process of cast iron to achieve low riser and no riser casting of gray cast iron and ductile iron parts.

(2) In the production of solid casting, polystyrene foam is used for shaping with self hardening sand using epoxy resin. When the molten metal is poured into the mold, the foam plastic pattern will vaporize under the action of the high-temperature molten metal, burn and disappear, and the molten metal will replace the position occupied by the original foam plastic, and will be cooled and solidified into a full mold casting with the same shape as the pattern.

(3) Relatively speaking, lost foam casting has great advantages over traditional sand molds for producing single or small batches of automotive coverings, machine tool beds, and other large molds. It not only saves expensive wood mold costs, but also is easy to operate, shortens production cycles, improves production efficiency, and has advantages such as small size, small machining allowance, and good surface quality.