Rapid casting method and process flow of tractor small parts

The mold free digital precision forming machine is used to realize the milling and forming of glass sand and resin sand mold sand core for casting, the 500 kg medium frequency melting furnace is used to melt the metal, and the sand casting manual molding line is used to assemble, mold and pour the mold core (as shown in the figure). Spectrometer, microscope and performance test equipment are used for composition control and performance detection in front of the furnace.

(a) Digital dieless casting precision forming machine (b) 500 kg medium frequency smelting furnace (c) Manual molding line

This paper mainly studies the rapid casting process of tractor small parts, sand blank forming method, rapid casting process design and rapid core forming method. Select small parts of tractor distributor shell and brake pull arm to complete rapid casting verification and casting inspection.

Small tractor parts are generally cast iron or steel castings, and the surface roughness is generally required to be RA ≤ 25 μ M or RA ≤ 50 μ m. Dimensions without tolerance indications shall be accepted according to CT10. The rapid casting of tractor small parts should adopt sand casting method, and there are basic tooling such as manual molding line. The following factors shall be considered in the design of rapid casting process:

① In order to realize the core forming by using the material reduction manufacturing method of die-free precision forming, the factors such as the size of the forming machine, the manufacturing capacity and handling of the sand blank need to be considered;

② The quantity of small batch manufacturing is generally 2 ~ 20 pieces, with small size and relatively simple process difficulty. It is necessary to focus on the production efficiency and design the production process of one box with multiple pieces. According to the above two factors, it is necessary to determine the conventional size of sand blank to ensure the forming efficiency of sand mold and sand core and the casting process yield.

According to many tests, too large sand billets are prone to many adverse conditions, such as uneven curing, inconvenient handling and dangerous lifting process. Control the size of sand blank to 1000 mm × 1 000 mm × About 300 mm, which can ensure the process yield of castings and the necessary manual core assembly molding process. The specific size of the sand blank shall be determined according to the design of the casting process. Generally, the sand consumption of more than 50 mm shall be ensured. In addition to the above factors, the production of sand blank requires sand mixer, adjustable square size core box mold, scraper and other tooling, the transfer of sand block requires forklift or crown block and other tools, and the core forming process requires sand box, measuring tool and dirt strip. Combining CAD design, material reduction manufacturing and sand casting method, the rapid casting process of tractor small parts is determined.