1. Principles of selection of fine benchmarks
1. The principle of datum coincidence: The design datum of the machined surface should be selected as the precise datum as much as possible, which can avoid the positioning error caused by the misalignment of the datum.
2. The principle of mutual reference: when the positional accuracy between the two machined surfaces on the workpiece is relatively high, the method of repeated machining of the two machined surfaces as a reference to each other can be used.
3. Self-base principle: some surface finishing processes require small and uniform machining allowances, and the machined surface itself is often used as the fine base.
4. Unified datum principle: as many surfaces as possible on the workpiece should be machined with the same set of fine datums as much as possible to ensure the relative positional accuracy between the machined surfaces.
The above four principles for selecting rough benchmarks can sometimes not be taken into account at the same time, so the main decision should be made.
2. Principles of selection of rough benchmarks
1. A rough benchmark should be used in one process of workpiece processing. Whether the rough benchmark is selected correctly or not is not only related to the processing of the first process, but also has a significant impact on the entire process of workpiece processing.
2. The principle of rationally allocating machining allowances: Considering ensuring that the machining allowances of important surfaces are uniform, important surfaces should be selected as rough benchmarks.
3. The principle that rough benchmarks should not be reused in general.
4. The principle of easy clamping: In order to stabilize the positioning of the workpiece and the clamping is reliable, the selected rough datum is required to be as smooth and clean as possible. Forging flashes, pouring riser cuts or other defects are not allowed, and there must be enough support area.Read More →