Gear grinding is usually used as the last process of finishing the hard tooth surface of gear, so as to comprehensively correct the errors before gear grinding and obtain high gear accuracy.

The most important gear grinding is divided into two categories: developing and forming grinding. Developing and forming grinding is divided into big plane grinding wheel grinding, conical grinding wheel grinding, double disk grinding wheel grinding teeth and worm grinding wheel grinding teeth. Worm grinding wheel tooth grinding as the most important tooth grinding technology in the automobile industry, now, the rapid development of high-speed worm grinding technology, greatly improve the grinding efficiency, greatly reduce the single cost of gear grinding.

With the rapid development of the automobile industry, especially the electric vehicle, higher requirements are put forward to improve the load of the gear, reduce the transmission noise and improve the power density. The grinding process to solve the tooth surface distortion is gradually widely used in the automobile industry.

Generating method

Worm grinding wheel grinding teeth

The teeth of worm grinding wheel are essentially meshed by a pair of helical gears, and the normal base of worm is equal to the normal base of grinding gear. In the grinding process, the continuous division of gear is synchronized with the rotation of grinding wheel, and the tooth shape is continuously developed. High production efficiency, suitable for mass production.

Flat grinding wheel

The grinding wheel grinding machine is the principle of the gear of the rack and the gear, and the principle of the method is used to process the gear. When grinding the gear, it is the same as the gear and the straight rack. When grinding the gear, it corresponds to the meshing of the helical gear and the diagonal rack. The machine tool structure is simple, the machining precision is very high, it is widely used to grinding the gear cutter, the gear cutter, and the high precision tooth surface of the standard gear.

Conical grinding wheel

Grinding wheel section shape trimming the tooth section shape of the rack, grinding and gear meshing movement, additional stroke movement grinding out the whole tooth width, in the grinding process, the knuckle line of the rack.

Disk wheel

The disc grinding wheel adopts the structure of double grinding wheel. The narrow edges of two grinding wheels are used to grind the involute teeth on both sides of the teeth at the same time. The two working edges form two corresponding tooth surfaces of the imaginary rack, and the inclination Angle of the grinding wheel forms the pressure Angle of the imaginary rack..

Tooth surface distortion 

Tooth surface distortion is a unique geometric phenomenon in the grinding process of all helical gears with tooth direction modification. No matter it is common for forming wheel grinding and worm wheel grinding, tooth surface distortion will occur. This manufacturing error cannot be avoided when space meshing is not changed.

In the process of grinding the worm wheel and the gear meshing movement, when the spur gear tooth direction modification, the grinding movement track of the sand wheel shaft along the tooth direction is parallel to the gear shaft, the contact track of the grinding wheel and the gear is coincided with the tooth involute, the tooth direction modification movement track is close to the theoretical curve, so there is almost no distortion. When grinding helical gear, the contact trace between grinding wheel and gear is slant. FIG. 5 shows the track movement of the grinding wheel along the trim curve, that is, the interpolation movement along the radial direction of the gear along the stroke movement of the grinding wheel shaft, which results in different grinding amounts at the top and root of the tooth at the same height, resulting in overcutting at one end and undercutting at the other end. The tooth direction measurement through multi-section can be intuitively reflected in the tooth Angle error.

The main factors influencing the tooth surface distortion

1) The size of spiral Angle affects the contact trace of grinding wheel and gear. Generally, the larger the spiral Angle is, the larger the distortion amount is. 2) The number of teeth has a significant influence on the shape of the tooth shape. In the case of the same modulus, the number of teeth affects the curvature of the tooth shape. The smaller the number of teeth, the smaller the radius of the involute curvature.

3) The larger the modulus, the larger the tooth width, the longer the contact trace and the larger the distortion amount.

4) The larger the drum shape, the larger the tooth surface distortion.

Why reduce tooth surface distortion?

Gear design engineers usually do not want the tooth surface distortion caused by such manufacturing errors, because the tooth surface distortion will cause a series of problems, such as the larger clearance of the tooth side, the increase of transmission vibration and impact, the reduction of transmission accuracy, and the increase of working noise. Therefore, reducing and optimizing tooth surface distortion has obvious positive significance. As shown in Figure: The optimized tooth surface has good contact in the meshing area of the tooth surface (increasing the overlap), which improves the load bearing, transmission accuracy, noise and service life of the gear.

The significance of high performance grinding wheel to control the grinding process of compensating tooth surface distortion

Grinding wheel usually plays an important role in grinding process. With the rapid development of worm grinding technology, the grinding line speed of the grinding wheel reaches 80m/s or even 100m/s, and the rotational speed of the workpiece shaft also increases. The high-speed grinding technology of the gear puts forward extremely high requirements on the grinding wheel, that is, good cutting performance should be maintained to ensure high material removal rate during high-speed grinding, and good shape keeping ability of the grinding wheel is required to ensure the geometric precision of the gear Degrees. Compared with the standard worm grinding process, the grinding process with tooth surface distortion control compensation puts forward better requirements on the grinding wheel, mainly in the following aspects :

1) The grinding process with tooth surface distortion control requires the grinding wheel to have better contour conformal ability to ensure the accuracy of the distortion compensation; 

2) The grinding process with tooth surface distortion control has a lower utilization rate of grinding wheel than the standard grinding process, and the life of grinding wheel will be significantly reduced, while the dressing cost will increase accordingly. Therefore, how to reduce the cost of a single tool, need longer life and better grinding performance of the grinding wheel.