초록 ▼

A flexible and resilient positive pattern is made for a desired high temperature metal or ceramic part such as a gas turbine impeller having a complex geometry with walls defining undercut spaces, and the pattern with flexible walls is dipped into a ceramic molding media capable of drying and harden

A flexible and resilient positive pattern is made for a desired high temperature metal or ceramic part such as a gas turbine impeller having a complex geometry with walls defining undercut spaces, and the pattern with flexible walls is dipped into a ceramic molding media capable of drying and hardening. The pattern is removed from the media to form a ceramic layer on the flexible pattern, and the layer is coated with sand and air dried to form a ceramic layer. The dipping, sanding and drying operations are repeated several times to form a multiple layer ceramic shell. The flexible wall pattern is removed from the shell, by partially collapsing with suction if necessary, to form a first ceramic shell mold with a negative cavity defining the part and to provide for reusing the pattern. A second ceramic shell mold is formed on the first shell mold to define the back of the part and a pour passage, and the combined shell molds are fired in a kiln. A high temperature casting material is poured into the shell molds, and after the casting material solidifies, the shell molds are removed by breaking the molds.

대표청구항 ▼

[ The invention having thus been described, the following is claimed:] [1.] A method of producing an impeller of a high temperature casting material and having a complex geometry with curved blades defining undercut spaces, the method comprising the steps of forming a positive flexible pattern of th

[ The invention having thus been described, the following is claimed:] [1.] A method of producing an impeller of a high temperature casting material and having a complex geometry with curved blades defining undercut spaces, the method comprising the steps of forming a positive flexible pattern of the impeller with a curable resilient and flexible material to provide the pattern with flexible walls corresponding to the blades, dipping the flexible pattern into a liquid ceramic molding media capable of drying and hardening, removing the flexible pattern from the liquid ceramic molding media with a coated layer of the ceramic molding media, drying the layer of ceramic molding media on the flexible pattern to form a ceramic shell on the flexible pattern, repeating the dipping and drying steps to form a multiple layer ceramic shell on the flexible pattern, removing the flexible pattern from the ceramic shell by flexing the walls of the flexible pattern to form a first multiple layer ceramic shell mold defining a negative mold cavity corresponding to the impeller and to provide a reusable flexible pattern, forming a second pattern defining a back plate surface for the impeller and a sprue passage, dipping the second pattern into a liquid ceramic molding media, removing the second pattern from the liquid ceramic molding media with a coated layer of the ceramic molding media on the second pattern, drying the layer of ceramic molding media to form a ceramic shell on the second pattern, and repeating the dipping and drying steps to form a multiple layer ceramic shell on the second pattern to form a second multiple layer ceramic shell mold, connecting the second ceramic shell mold to the first ceramic shell mold, removing the second pattern from the second mold, pouring the casting material into the negative mold cavity of the first ceramic shell mold through the sprue passage within the second ceramic shell mold and allowing the casting material to harden to form a multiple blade impeller with a back plate, and removing the first and second shell molds from the impeller.