Dalian precision parts processing accuracy refers to the degree to which the actual geometric parameters (size, shape and location) of the parts after processing conform to the ideal geometric parameters specified in the drawings. The higher the degree of coincidence, the higher the processing accuracy. In the process of machining, because of the influence of various factors, it is impossible to process every geometric parameter of a part exactly in accordance with the ideal geometric parameters, and some deviations will always occur. This deviation is the processing error.

       Sand is used as casting material, also known as sand casting, sand turning, including wet sand mold, dry sand mold and chemical hardening sand mold, but not all sand can be used for casting. The advantage is that the cost is low, because the sand used in the casting die can be reused; the disadvantage is that the casting die itself can not be reused, and the finished product can only be obtained after destruction.

       The required metal components are extracted from ores by chemical methods, and then metals are prepared by water solution electrolysis and other methods. This method is mainly used in low-grade, refractory or micro-powder ores. At present, 75% of zinc and cadmium in the world are produced by roasting - Leaching - aqueous solution electrolysis.