The positioning of the workpiece is achieved by the contact between the positioning surface on the workpiece and the V-block of the positioning element on the fixture.Positioning datum is the datum on which the workpiece is positioned and is reflected by the positioning datum.
The function of positioning element is to make the workpiece have accurate and fixed position in the fixture and to limit enough freedom under the condition of guaranteeing the processing requirements.
(1) Sufficient precision positioning elements should have sufficient precision to ensure the positioning accuracy of the workpiece.
(2) Better wear resistance. As the working surface of positioning element often contacts and rubs with the workpiece, it is easy to wear. Therefore, it is required that the working surface of positioning element has better wear resistance to maintain service life and positioning accuracy.
(3) The positioning element with sufficient strength and rigidity should not be deformed or damaged under the action of workpiece gravity, clamping force and cutting force. Therefore, it is required that the positioning element has sufficient rigidity and strength, otherwise the positioning accuracy of workpiece will be affected.
(4) The better technological positioning elements shall be easy to manufacture, assemble and maintain.
(5) The working surface shape of the chip locating element that facilitates removal of the chip should facilitate removal of the chip to prevent chip insertion from affecting accuracy.