When the accuracy of machine tool and hob meet the requirements, the fixture manufacturing and installation accuracy are the main factors affecting the gear machining accuracy. The rationality of the fixture structure is also related to the production efficiency. The fixture with reasonable structure design can also eliminate the geometric deviation of the machine tool and improve the installation accuracy of the workpiece. Therefore, in order to improve the accuracy of gears, in addition to high-precision equipment, cutting tools, gear blanks, there must be good structure and high-precision fixture.
1.The positioning datum shall be accurate and reliable, and the fit clearance between spindle and workpiece shall be appropriate. Otherwise, the geometric eccentricity will be produced during the installation of the gear blank, which will cause the accumulated errors of the circumferential pitch and the tooth profile errors of the gear to be processed;
2.If the fixture spindle is installed with the taper hole of the machine tool spindle as the installation reference, there is a requirement for concentricity between the positioning Journal of the spindle and the taper (generally less than 0.005 mm), and the taper must be grinded with the taper hole of the machine tool;
3.Each working plane of transition flange, gasket for clamping and both ends of pressing plate shall be parallel, and the diameter shall be smaller than the diameter of gear root circle.
4.Sufficient rigidity and clamping force;
5.Simple structure, easy to manufacture;
6.Ensure a certain service life, i.e. the reference plane shall be wear-resistant;
7.In order to adapt to the characteristics of more varieties and less quantity of small module gears, it is necessary to have certain universality.