How does the foundry determine the machining allowance of the casting

Casting machining allowance in the production of casting mold is to be carefully studied according to the size of the casting, the division of the processing surface, the casting drawings marked with processing symbols must be placed in the place of machining allowance, and there is no processing symbol where only the shrinkage is placed. It is also necessary to combine the molding process to determine the size of the machining allowance, the manual modeling is generally slightly larger, and the machining allowance of the molding machine molding process can be appropriately reduced (because the molding machine is more accurate).

The relatively large holes or grooves on the casting can be brought out when making the mold, and a certain casting machining allowance is left for finishing cutting. This can reduce the casting cost. For example, a hole with a diameter of 100mm for the installation of an anchor on a cast iron platform can be cast into a hole with a diameter of 80mm, leaving a machining allowance of 10mm on one side. Only 10mm allowance is processed during machining, which not only saves the casting cost, but also saves the processing time.

Nowadays, many customers only provide machining drawings, and rarely provide casting drawings. Because the user unit cannot accurately cast the unit with what kind of modeling casting process is used for casting, it is impossible to give accurate casting drawings. After receiving the casting order, the foundry manufacturer determines the casting process with reference to the GBT6414-1999 casting tolerance and machining allowance standard, and then combines years of production experience to place the machining allowance. Therefore, the machining allowance of castings is generally determined by the foundry manufacturer.