When processing parts on a CNC lathe, in order to ensure the processing accuracy of the parts, it is crucial to choose the correct positioning datum. The principles of CNC lathe positioning datum will be introduced to you in detail.

Principles for benchmark selection:

1. The principle of unified datum: During the processing process, the same datum should always be used as the benchmark for measurement as much as possible, so as to ensure the processing accuracy and assembly accuracy of the parts.

2. Principle of datum coincidence: Try to make the design datum and positioning datum coincide with each other to reduce errors caused by non-coincidence of the datum. 3. The principle of mutual reference: When the mutual position accuracy of two surfaces is high, the principle of mutual reference can be adopted to repeatedly process one of the surfaces.

4. Principle of ease of measurement: The selected positioning datum should be easy to measure to improve measurement accuracy.

5. Principle of good stability: The positioning base surface should have sufficient stability to ensure the stability of the processing process.

Selection of positioning datum:

1. Use the hole on the workpiece as the positioning reference: When there is a hole on the workpiece, you can select the hole as the positioning reference. In this way, the accuracy of the hole itself can be used to improve the machining accuracy.

2. Use the outer circle of the workpiece as the positioning datum: When the outer circle precision of the workpiece is high, the outer circle can be selected as the positioning datum. In this way, the accuracy of the outer circle can be used to ensure the accuracy of processing.

3. Use the end face of the workpiece as the positioning datum: When the end face precision of the workpiece is high, the end face can be selected as the positioning datum. In this way, the flatness of the end face can be used to ensure the stability of processing.

In short, when processing parts on a CNC lathe, it is crucial to choose the correct positioning datum. Following the above principles, the machining accuracy and assembly accuracy of parts can be effectively improved, thereby improving product quality and competitiveness.