# Study on precision forming process of bevel gear by cold rotary forging

The cold rotary forging precision forming process of bevel gear is an advanced manufacturing technology. Its process design in actual production includes blank preparation, bevel gear forging design, rotary forging force calculation, determination of rotary forging machine tonnage, determination of rotary forging process parameters (including swing head inclination, reduction per turn, rotary forging motion track and other parameters), electrode design and concave model cavity design. This chapter analyzes and studies the above problems, and puts forward the calculation method or determination principle of corresponding process parameters. These calculation methods and principles will be used as the basis for the calculation and decision-making of process aided design in gearcapp system, as well as the basis for the determination of geometric relationship in parametric CAD modeling.

(1) In EDM, the machining time of the small end and tooth top of the electrode gear is long, and its loss is larger than that of the tooth root and big end, so that the thickness of the tooth top is relatively thinner, resulting in the distortion of the tooth profile involute, which is reflected in the increase of the pressure angle. Therefore, when designing the electrode gear, the pressure angle should be reduced accordingly. According to the formula: the pressure angle of the tooth profile of the die is α 0, the pressure angle of the tool electrode gear shall be:

(2) Due to the influence of discharge gap in EDM, negative displacement machining should be carried out based on the die cavity involute (i.e. the involute of bevel gear parts) to obtain the electrode tooth profile; At the same time, due to the influence of electrode burning, the tooth thickness of the electrode is thinned and the diameters of tooth top circle and tooth root circle are reduced, the electrode gear should be processed accordingly. Considering comprehensively, the displacement of the two can be algebraically superimposed, that is:

However, during electrode finishing, the electrode burning loss w · h is generally about 0.18 mm, and the discharge gap accounts for δ At 0.05-0.06 mm, the displacement is Σ Δ H is on the order of 0.01 mm. This value is very small in actual machining, so the displacement of displacement machining can be ignored.

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