In the process standard design of CNC precision parts processing, the correct selection of positioning data has a crucial impact on ensuring the processing requirements of CNC precision parts and arranging the processing sequence reasonably.

The positioning reference is divided into fine reference and coarse reference: the coarse reference uses the unprocessed surface on the blank as the positioning reference. The precision reference is based on the machining surface.

1、 Criteria for selecting precise benchmarks

1.Baseline coincidence criteria: The processed surface design data should be selected as accurately as possible to prevent positioning errors caused by data misalignment.

2.Consistent reference criteria: In order to ensure the relative positioning accuracy between the machined surfaces of parts, as many surfaces as possible on the workpiece should be processed using the same set of fine benchmarks as much as possible.

3.Principle of mutual reference between workpiece machining surfaces: The repeated machining method of two machining surfaces can be used as a mutual reference.

4.Self reference criteria: Some surface finishing processes require small and uniform machining tolerances, often using the machined surface itself as a precision reference.

The four criteria for selecting good benchmarks mentioned above cannot sometimes be met simultaneously, and must be determined based on actual situations.

2、 Criteria for selecting coarse benchmarks

1.When processing a workpiece for the first time, it is necessary to use a rough benchmark. Whether the selection of the rough benchmark is correct is not only related to the processing of the first process, but also has a significant impact on the entire process of the workpiece.

2.Reasonable allocation criteria for machining tolerances: The machining allowance on the workpiece surface should be kept uniform, with important surfaces as a rough benchmark.

.Standard for easy clamping: In order to ensure stable positioning and secure clamping of the workpiece, it is required to select an approximate reference point that is as smooth and clean as possible, without lightning strikes, forging cuts, or other shortcomings, allowing for a sufficient support area.