In CNC machining of aluminum shell, the selection of positioning standard determines the quality of aluminum parts. The requirements for dimensional accuracy and mutual position accuracy of aluminum parts greatly affect the arrangement of machining sequence between parts surfaces. When the workpiece is equipped with a fixture, the selection of positioning criteria will also affect the complexity of the fixture structure. This requires that the fixture can bear large cutting force and meet the requirements of positioning accuracy. Therefore, the selection of positioning standard is an important technological problem.

Firstly, it depends on the standards used in the design of aluminum parts.

Secondly, cross-parameter datum, that is, if the position between the two machined surfaces on the workpiece requires high accuracy, it needs to be completed by cross-parameter repetitive machining method on the two machined surfaces;

Thirdly, when cross-positioning, we should design multi-reference positioning fixture to prevent the positioning standard from changing, and also check the processing quality of the previous process to prevent the defects of the previous process from causing processing problems.

When the design standard for positioning aluminum parts in aluminum shell CNC machining center is basically difficult to match, the assembly drawing should be analyzed to determine the design function of the design standard for aluminum parts and the tolerance range between them. The positioning standard and design standard should be strictly determined through the calculation of dimension chain to ensure the machining accuracy.