Precision Standard For Precision Castings In Ningbo

- Mar 24, 2018-

The deviation of Ningbo precision casting geometry precision depends on the machining allowance, casting size and weight of the same amount of quantitative, under the same circumstances, precision machining and metal amount of workload from two aspects, reflects the advanced degree of precision casting process. The allowable deviation of size and weight and the machining allowance of castings are determined according to the GB6414-86GB/T11351-89GB/T11350-89 standard and the technical conditions of ordering, respectively. The actual deviation is determined by the data of the technical inspection department. The so-called size control of the castings is to control the discreteness of the measured values on the premise that the measured mean values are in accordance with the nominal size of the castings. This discrete-time cause is usually caused by random changes in the technical conditions of production and the properties of raw materials, or system errors. The precision castings should be judged according to the nature of the error and the corresponding countermeasures to improve the size accuracy to meet the requirements of the standard. Sometimes, only one or two sizes of the whole casting require strict dimensional tolerance, so it is not necessary to stipulate all dimensions according to the same level of tolerance. In order to improve the precision of casting grade, can generally use metal mold, it must transform other methods need to improve, such as the use of shell casting and other casting process, but will inevitably lead to increased cost of mold, the production preparation cycle is prolonged, the casting cost will be increased. When evaluating the geometric accuracy of castings, besides the allowance of machining surface allowance and the weight deviation of castings, the most representative tolerance range or deviation range of wall thickness and rib thickness should also be given. The required wall thickness of the structure is determined by the casting designer, and the minimum allowable wall thickness is determined by the foundry technician. In most cases, the designers of the precision casting decide to form the wall thickness marked on the pattern. The allowable deviation between the wall thickness and the actual wall thickness of the design is an important index for the characterization of the precision of the geometric shape of the castings

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