Precision shaft parts are a common type of component. Their structure is usually a rotating body, and they are generally longer than their diameter. They are widely used in many automated devices, and their function is to support transmission components, transmit torque and bear loads. HINCOX is a leading enterprise specializing in the customized processing and mass production of high-precision shaft parts. It has accumulated years of experience in the precision processing of shaft parts. Next, we will provide you with a detailed review of some issues to be noted during the processing of shaft parts, mainly from the aspects of pre-processing, processing routes, clamping, and positioning references. Let's take a look together.
Ⅰ. Pre-machining of shaft parts (assisted)
Before turning the outer circle of shaft parts, some preparatory procedures must be carried out first. This is the pre-processing process of shaft parts. The most important preparatory process is straightening. Because during the manufacturing, transportation and storage of workpiece blanks, bending and deformation often occur. To ensure reliable clamping and uniform distribution of machining allowances, straightening is carried out in the cold state through various presses or straightening machines, which is conducive to the machining accuracy in the later stage.
Ⅱ. Basic Processing Routes for Shaft Parts (Process Selection)
The main machining surfaces of shaft parts are the outer cylindrical surface and common special surfaces. Therefore, appropriate machining methods should be selected based on various precision grades and surface roughness requirements. Its basic processing routes can be summarized into four.
A. The processing route from rough turning to semi-precision turning and then to precision turning is also the most important process route selected for the processing of the outer circle of the needle of shaft parts made of commonly used materials.
B. From rough turning to semi-finish turning, then to finish turning, and diamond turning, this processing route is specifically designed for processing non-ferrous metal materials. This is because non-ferrous metals have relatively low hardness and are prone to clogging the gaps between sand grains. Grinding usually does not achieve the required surface roughness, and both finish turning and diamond turning processes must be adopted. The last processing route is from rough turning to semi-finishing turning, then to rough grinding and finishing grinding.
C. The processing route from rough turning to semi-finishing turning, then to rough grinding, and finally to finishing grinding is the best choice for ferrous metal materials and parts with high precision requirements, small surface roughness requirements and the need for hardening, because grinding is the most ideal subsequent processing procedure.
D. Perform finishing processing. This route is often adopted for parts made of ferrous metals that have been hardened, have high precision requirements, and have low surface roughness value requirements.
Ⅲ.Clamping of Shaft Parts (Processing Preparation)
The processing of conical plugs and conical sleeve mandrels must have high processing accuracy. The center hole is not only the positioning reference for its own manufacturing but also the reference for the fine processing of the outer circle of the hollow shaft. It is necessary to ensure that the conical surface on the conical plug or conical sleeve mandrels has a high coaxiality with the center hole.
Therefore, when choosing the clamping method, it should be noted that the installation times of the cone plug should be minimized as much as possible to reduce the repeated installation error of the parts. In actual production, after the conical plug is installed, it is generally not removed or replaced during the processing before it is completed.
Ⅳ. Positioning Reference for Shaft Parts Processing (Processing Process)
A. Take the center hole of the workpiece as the positioning reference for processing. In the processing of shaft parts, the coaxiality of especially circular surfaces, conical holes, and threaded surfaces, as well as the perpendicularity of end faces to the rotation axis, are all important manifestations of positional accuracy. These surfaces are generally designed with the centerline of the axis as the reference, and are positioned by center holes, which conforms to the principle of reference coincidence.
The center hole not only serves as the positioning reference during turning operations but also acts as the positioning and inspection reference for other processing procedures, conforming to the principle of unified reference. When two-center hole positioning is adopted, it is also possible to process multiple outer circles and end faces to the greatest extent in one clamping.
B. Take the two outer circular surfaces as the positioning reference for processing. When processing the inner hole of a hollow shaft, the center hole cannot be used as the positioning reference. Therefore, the two outer circular surfaces of the shaft should be used as the positioning reference. When processing the spindle of a machine tool, the two supporting journal shafts are often used as positioning references. This can effectively ensure the coaxiality requirement of the taper hole relative to the supporting journal shafts and eliminate the error caused by the non-coincidence of the references.
C. Use the outer circle and the center hole as the positioning reference for processing. This method effectively overcomes the drawback of poor rigidity in the center hole positioning. Especially when processing heavier workpieces, the center hole positioning can cause unstable clamping, and the cutting parameters cannot be too large. If the outer circle and the center hole are used as the positioning reference, there is no need to worry about this problem. During rough machining, the method of using the outer surface of the shaft and a central hole as the positioning reference can withstand a relatively large cutting torque during processing and is the most common positioning method for shaft parts.
D. Use a cone plug with a central hole as the positioning reference for processing. This method is most commonly used in the processing of the outer cylindrical surface of hollow shafts.
Through the above analysis, we can effectively avoid and prevent the common problems often encountered in the processing of shaft parts, and the processing efficiency and accuracy can also be well guaranteed.
