Technical Considerations for Precision Machining of Shaft Components

Precision shaft components are a common type of part, typically characterized as rotating bodies with lengths greater than their diameters. They are widely used in various automation equipment to support transmission components, transmit torque, and bear loads. Shenzhen PANS Technology Co., Ltd. is a leading enterprise specializing in the custom machining and mass production of high-precision shaft components. Drawing from years of experience in precision shaft machining, we will detail several key technical issues to consider during the machining process, focusing on pre-machining, machining routes, clamping methods, and positioning references.

1. Pre-Machining for Shaft Components (Preparation)

Before turning the outer diameter of shaft components, it is essential to perform preliminary operations, known as pre-machining. The most critical preparatory step is straightening, as the workpiece blank often experiences bending and deformation during manufacturing, transportation, and storage. To ensure reliable clamping and uniform distribution of machining allowances, the blank must be straightened using various presses or straightening machines while cold, which aids in achieving the desired machining precision.

2. Basic Machining Routes for Shaft Components (Process Selection)

The main surfaces to be machined on shaft components are the outer diameter and various special surfaces. Therefore, suitable machining methods should be selected based on different precision levels and surface roughness requirements. The basic machining routes can be summarized as follows:

a. From rough turning to semi-finish turning, and finally to finish turning. This is the primary process route for machining the outer diameter of shaft components made from commonly used materials.

b. From rough turning to semi-finish turning, followed by finish turning and diamond turning. This route is specifically designed for machining non-ferrous metal materials, which tend to have lower hardness and may block the voids between abrasive grains. Thus, grinding may not achieve the required surface roughness, necessitating the use of finish turning and diamond turning.

c. From rough turning to semi-finish turning, then to rough grinding, and finally finish grinding. This route is optimal for ferrous metal materials requiring high precision, low surface roughness, and hardening, as grinding is the ideal follow-up machining process.

d. For finishing operations, this route is commonly used for ferrous materials that have been hardened, requiring high precision and low surface roughness values.

3. Clamping Methods for Shaft Components (Preparation for Machining)

Machining of tapered plugs and tapered mandrels requires high precision. The center holes serve not only as positioning references for their manufacturing but also as the reference for the precision machining of hollow shaft outer diameters. It is crucial to ensure that the taper surfaces of the tapered plugs or mandrels maintain high coaxiality with the center holes.

When selecting clamping methods, it is essential to minimize the number of installations for tapered plugs to reduce repeat installation errors. In practical production, tapered plugs are generally not removed or replaced during the machining process until completed.

4. Positioning References for Machining Shaft Components (Machining Process)

a. Using the workpiece's center hole as a positioning reference. In the machining of shaft components, the coaxiality of outer surfaces, tapered holes, and threaded surfaces, as well as the perpendicularity of end faces to the rotation axis, reflect positional accuracy. These surfaces are generally designed based on the axis's centerline, and positioning with the center hole adheres to the principle of reference overlap.

The center hole serves not only as a positioning reference during turning but also as a reference for other machining processes and inspections, adhering to the principle of unified references. When using two center holes for positioning, multiple outer diameters and end faces can be machined in a single clamping operation.

b. Using two outer diameter surfaces as positioning references. When machining the inner hole of a hollow shaft, the center hole cannot be used as a positioning reference; hence, the outer diameter surfaces of the shaft should be utilized instead. In the machining of machine spindle shafts, the two supporting journal necks are often used as positioning references, effectively ensuring the coaxiality of the tapered hole relative to the supporting journal necks and eliminating errors due to reference misalignment.

c. Using the outer diameter and center hole as positioning references. This method effectively overcomes the rigidity issues associated with center hole positioning, particularly when machining heavier workpieces, as center hole positioning may lead to instability during clamping and limit cutting amounts. Using the outer diameter and center hole as references mitigates this issue. During rough machining, employing the outer diameter surface and a center hole as positioning references allows for greater cutting torque, making it the most common positioning method for shaft components.

d. Using a tapered plug with a center hole as a positioning reference. This method is most commonly applied when machining the outer diameter surface of hollow shafts.

Through the analysis above, we can effectively avoid and prevent common issues encountered in shaft component machining, ensuring excellent efficiency and precision. Shenzhen PANS Technology has introduced multiple CNC Swiss machines, offering numerous advantages in the precision machining of shaft components. The unique structure of CNC Swiss machines maintains the precision and coaxiality of long shaft products effectively while enabling side milling and cross-sectional milling in a single clamping operation, a capability not possessed by conventional CNC lathes.