Causes of gear machining error

Causes of gear machining error

1. Gear machining error

All kinds of errors generated in gear cutting can be summarized into the following four types: ① radial machining error: the change of radial distance between cutter gear cutting wheels; ② Tangential machining error: machining error caused by damage or inaccurate indexing of the generating motion between the tool and the workpiece; ③ Axial machining error: the error of the tool moving along the workpiece axis; ④ The error of the production surface of the gear cutter.

1. Radial machining error

The radial error of gear cutting is caused by the positioning error of the gear blank on the machine tool, the radial runout of the tool, and the periodic change of the position of the gear blank shaft or the tool shaft (table swing).

(1) Geometric eccentricity caused by the positioning error of gear blank: the so-called geometric eccentricity refers to the misalignment of the rotating shaft during gear processing (or inspection).

(2) Cutter installation error: ① hob installation error: when machining spur gear, hob installation error forms tooth shape error, destroys gear working stability, and reduces tooth height contact area. When machining helical gears, hob installation error forms contact line waviness and reduces tooth contact area. ② Installation error of gear shaper cutter: the radial runout of gear shaper cutter shaft, the installation eccentricity of gear shaper cutter and the radial runout of gear shaper cutter itself comprehensively lead to the radial runout of gear shaper cutter, or the gear shaper cutter has geometric eccentricity. This kind of eccentricity will not only lead to the radial error of the gear, but also have a great impact on the length of the common normal. In addition to the above errors, the radial runout of the gear shaper cutter will also cause errors in the cutting area of the cutting gear.

2. Tangential machining error

For gear hobbing and gear shaping, the tangential error of tangential machining is mainly caused by the damage of tool and gear blank. The error of each part of the machine tool kinematic chain is mainly the error of the indexing worm gear pair, which is the root of the tangential error. The error of indexing worm gear makes the meshing of cutting gear and hob produce motion deviation.

3. Axial machining error

The axial error of gear cutting is mainly caused by the inaccuracy of the machine tool guide rail and the skew of the gear blank axis. In some cases, the kinematic chain of the machine tool will also be affected.

4. Error of tool production surface

The error of the tool production surface is caused by the approximate shape of the tool production surface and its manufacturing and grinding errors. The tooth shape angle error of the tool production surface causes the base pitch error of the workpiece and the direction error of the contact line, affects the working stability of the spur gear, and destroys the tooth surface contact between the spur gear and the helical gear.