Tooth Deformation Law of Cylindrical Helical Gear during Hot Precision Forging

Cylindrical helical gears are widely used in ship, automobile, aviation and other industries because of their smooth transmission, good engagement and large bearing capacity.Traditional cutting and machining methods for cylindrical helical gears have the features of low material utilization, long production cycle, high production cost and low mechanical properties of products, which make it difficult to meet the requirements of the development of automobile and mechanical industry in China.As a near net shape technology, precision forging technology has the advantages of high material utilization, short production cycle and low energy consumption.

Using forging technology to produce cylindrical helical gears can improve material utilization and mechanical properties of products.Nevertheless, there are still some problems to be solved urgently in the forging of cylindrical helical gears, the main ones being unsatisfactory filling of corners at the later stage of forming and high forming load.

Cai et al. proposed floating die structure to provide positive friction for blank forming, thus improving tooth filling and reducing forming load to a certain extent.According to the principle of positive friction and restraint shunt flow, Liu Xia studied several forging forming processes of spur gear. The analysis shows that positive friction can improve the forming load and filling quality of precision forging of spur gear. When using hollow shunt blank, the forming load of spur gear is smaller and the filling quality is better.

Feng Wei et al. used floating die structure to form helical gear. They studied different convex die speeds and die speeds. They found that floating die structure is beneficial to reduce the forming force. When the die speed is higher than the downward speed of the convex die, the tooth forming effect is better.Jung et al put forward a two-step forming process, which firstly forms spur gear and then twists the spur gear blank to helical gear. The test proves that this process can effectively reduce the forming load.

Metal streamlines can be used to study metal flow deformation laws. Metals with uniform streamlines have better mechanical properties.Therefore, many scholars control the flow and deformation of metal by optimizing the process to obtain products with uniform streamline.In this paper, a heat transfer-deformation coupling finite element model for cylindrical helical gear hot forging is established by Deform-3D software. Through flow-net function of Deform-3D, metal flow laws at different forming stages and locations are obtained. Coordinate grid tests are carried out with lead samples to obtain metal flow laws of cylindrical helical gear and to verify the reliability of the finite element model.

Scroll to Top