US 4,048,709 AGranted

Method of casting

AssigneeConval-Penn, Inc.

InventorHoward H. Deem

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Abstract

A method is disclosed for producing cast metal parts having smooth surfaces held to close dimensional tolerances, eliminating the need for machining. The method includes making a core box and pattern to closer tolerances than the finished part, producing a sample core and mold using sand of predetermined characteristics under regulated conditions. The sample core is precisely assembled with the sample mold and gauged. Thereafter, a prototype part is cast at a controlled temperature and cooled for a controlled time. The dimensions of the prototype part are compared with desired dimensions and the core box and pattern are modified where required. They are subsequently used to make production cores and molds formed from same sands under same conditions previously employed. The production cores and molds are accurately assembled and gauged and production parts cast at the same temperature previously used and are cooled as before.

The method of sand casting a part having a smooth flat surface positioned within a predetermined tolerance, said method comprising the steps of:

(1) making a pattern incorporating a shrink factor, said pattern being dimensioned to a lesser tolerance than said predetermined tolerance;
(2) making a core box, said core box incorporating a shrink factor, said core box being dimensioned to a lesser tolerance than said predetermined tolerance;
(3) making a sample core using said core box, said core being made of sand of predetermined characteristics and being made under regulated time and temperature conditions;
(4) making a sample mold using said pattern, said mold being made of sand of predetermined characteristics and being made under regulated time and pressure conditions;
(5) assembling said sample core within said sand mold and accurately positioning said core, gauging said core to determine that it is properly positioned within said mold;
(6) pouring metal into said mold at a predetermined temperature to cast a prototype part and allowing said metal to cool for at least a predetermined time;
(7) comparing the dimensions of said prototype part with the desired dimensions thereof;
(8) modifying said core box and said pattern in any areas where the dimensions of said prototype part differ from the desired dimensions thereof;
(9) producing production sand cores from said modified core box using sand having substantially the same characteristics utilized to produce the sample core and utilizing the same time and temperature conditions;
(10) producing production sand molds using said modified pattern, said molds being made from sand having the same characteristics utilized in producing the sample mold and utilizing the same time and pressure conditions;
(11) assembling said production cores within said production molds and accurately positioning said cores within said molds, gauging said cores to determine that they are properly positioned to cast a production part;
(12) pouring metal into said mold at substantially the same temperature as used to cast the sample part and removing said production part from said mold after said predetermined cooling time.

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Abstract

Claims6