Part 1: Gear and shaft parts

1. Gear machining process flow

According to different structural requirements, the main process flow for gear parts processing is forging blank → normalizing → precision turning → gear shaping → chamfering → gear hobbing → gear shaving → (welding) → heat treatment → grinding → meshing adjustment.

After heating, the tooth part is generally not processed, except for the main and auxiliary teeth or parts that customers require to grind.

2. Axis process flow

Input shaft: forging blank → normalizing → precision machining → tooth rubbing → drilling → tooth insertion → chamfering → gear hobbing → gear shaving → heat treatment → grinding → meshing adjustment.

Output shaft: forged billet → normalizing → precision machining → tooth rolling → gear shaving → heat treatment → grinding → meshing adjustment.

3. Specific process flow

(1) Forging blank

Hot die forging is a widely used blank forging process for automotive gear components. Previously, hot forging and cold extrusion blanks were widely used, but in recent years, cross wedge rolling technology has been widely promoted in shaft processing. This technology is particularly suitable for making complex stepped shaft billets, as it not only has high accuracy, small post-processing allowance, but also high production efficiency.

(2) Normalization

The purpose of this process is to obtain hardness suitable for subsequent gear cutting and prepare the microstructure for final heat treatment, in order to effectively reduce heat treatment deformation. Due to the significant influence of personnel, equipment, and environment, the cooling speed and uniformity of workpieces are difficult to control in general normalizing, resulting in large differences in hardness and uneven metallographic structure, which directly affects machining and final heat treatment.

(3) Precision machining

In order to meet the positioning requirements of high-precision gear machining, CNC lathes are used for precision turning of gear blanks. The gear first undergoes machining of the inner hole and positioning end face, and then the machining of the other end face and outer diameter is completed synchronously. It not only ensures the perpendicularity requirements between the inner hole and the positioning end face, but also ensures small size dispersion in large-scale production of gear blanks. This improves the accuracy of the gear blank and ensures the machining quality of the subsequent gears.

There are three main methods for locating and clamping axis parts during machining:

1. Positioning with the center hole of the workpiece: In the machining of the shaft, the coaxiality of the outer circular surfaces and end faces of the part, as well as the perpendicularity of the end face to the rotation axis, are the main factors affecting their relative positional accuracy. The design reference for these surfaces is generally the centerline of the shaft. If two center holes are used for positioning, it conforms to the principle of overlapping reference points.

2. Using the outer circle and center hole as the positioning reference (one clamp and one top): Although using two center holes for positioning has high centering accuracy, its rigidity is poor, especially when processing heavier workpieces, it is not stable enough, and the cutting amount cannot be too large. During rough machining, in order to improve the stiffness of the parts, the outer surface of the shaft and a central hole can be used as the positioning reference for machining. This positioning method can withstand large cutting moments and is the most common positioning method for shaft parts.

3. Using the two outer circular surfaces as the positioning reference: When machining the inner hole of a hollow shaft (such as machining the inner hole of a Morse taper on a machine tool), the center hole cannot be used as the positioning reference, and the two outer circular surfaces of the shaft can be used as the positioning reference. When the workpiece is a machine tool