About precision casting products accuracy standards

Precision casting accuracy depends on the geometry of the machining allowance, casting the same nominal size and weight deviation amount, under the same conditions as other occasions, from geometry precision machining and metal work both in terms of amount, reflecting the precision casting process sophistication of the process.
Size and weight tolerances and machining allowances for castings by GB6414-86GB/T11351-89GB/T11350-89 standards and technical conditions of the order decided respectively, while the actual data by the technical inspection department deviation determination. Size control is called casting and casting in the measured mean Subject to the nominal size, the degree of control of discrete measured values. This cause is usually due to the production of discrete technical conditions and material properties, such as random or systematic errors caused by the change. Precision casting judgment and appropriate countermeasures should be based on the nature of the error and improve the dimensional accuracy to meet the requirements of the standard.
Sometimes, the entire cast only one or two rough size requirements more stringent dimensional tolerances, then there is no need to press the same level of all sizes are specified tolerances. To improve casting accuracy level, generally use a metal mold, you need to be transformed significantly improve the modeling methods, such as using shell casting or other precision casting process, but it will inevitably lead to increased tooling costs, production preparation cycle extension, casting costs multiplied.
When assessing the accuracy of the casting geometry, in addition to processing face margin requirements need to add casting weight deviation, the most representative range of tolerance or deviation of wall thickness and muscle thickness should also be given. Wall thickness of the structure must be determined by the casting designer, the minimum allowable wall thickness is determined by the casting process division. In most cases, precision castings, designers decided to form a wall thickness marked on the pattern. This design allowed deviation between the actual wall thickness of the wall thickness and to characterize the geometry precision castings important indicator.