Shaft parts are a common type of parts. Its structure is a rotating body, and its length is generally greater than its diameter. It is widely used in various mechanical equipment to support transmission components, transmit torque and bear loads. The CNC machining of shaft parts should follow certain rules. This article will come to the specific processing steps and some problems that need attention.
1. The basic processing route of shaft parts
The main cnc machining surfaces of shaft parts are external circular surfaces and common special-shaped surfaces. Therefore, the most suitable machining method should be selected according to various accuracy levels and surface roughness requirements. The basic processing routes can be summarized into four.
1. The route from cnc rough machining to semi-finish machining to finish machining is also the most important process route chosen for the outer circle machining of shaft parts with common materials.
2. From rough turning to semi-finish cnc turning, then to rough grinding, and finally the fine grinding processing route. For ferrous metal materials and precision requirements, the surface roughness requirements are small and the parts that need to be hardened, this processing route It is the best choice, because grinding is the most ideal follow-up process.
3. From rough turning to semi-finishing turning, to fine turning and diamond turning, this processing route is specially used to process non-ferrous metal materials, because non-ferrous metals have low hardness and are easy to block the gaps between sand particles. Grinding is usually not It is easy to obtain the required surface roughness, and the process of fine turning and diamond turning must be adopted; the last processing route is from rough turning to semi-finishing turning, to rough grinding and fine grinding.
4. For finishing processing, this route has been hardened for ferrous metal materials, and requires higher precision, and parts with lower surface roughness requirements are a processing route that is often used.
2. Pre-processing of shaft parts
Before turning the outer circle of shaft parts, some preparation processes must be carried out. This is the pre-processing process of shaft parts. The most important preparation process is straightening. Because the workpiece blank is often bent and deformed during the manufacturing, transportation and storage process. In order to ensure reliable clamping and uniform distribution of laser cutting allowance, in cold state, various presses or straightening machines are used for straightening.
3. Positioning datum for machining shaft parts
1. Take the center hole of the workpiece as the positioning datum for machining. In the processing of shaft parts, the coaxiality of the outer surface, the tapered hole, and the threaded surface, and the perpendicularity of the end face to the axis of rotation are important manifestations of position accuracy. These surfaces are generally based on the centerline of the shaft as the design datum, and the center hole is used for positioning, which conforms to the principle of datum coincidence. The center hole is not only the positioning datum during turning, but also the positioning datum and inspection datum for other processing procedures, which conforms to the principle of standard uniformity. When two center holes are used for positioning, multiple outer circles and end faces can be cnc operating in one clamping to the maximum.
2. The outer circle and the center hole are used as the positioning datum for processing. This method effectively overcomes the shortcomings of poor positioning rigidity of the center hole, especially when processing heavier workpieces, the positioning of the center hole will cause unstable clamping, and the cutting amount cannot be too large. There is no need to worry about this problem if the outer circle and the center hole are used as the positioning reference. When roughing, the method of using the outer surface of the shaft and a center hole as the positioning reference can withstand a large cutting torque cnc manu facturing, which is the most common positioning method for shaft parts.
3. Take the two outer circular surfaces as the positioning datum for processing. When processing the inner hole of a hollow shaft, the center hole cannot be used as the positioning reference, so the two outer circular surfaces of the shaft should be used as the positioning reference. When machining the main shaft of a machine tool, the two supporting journals are often used as the positioning reference, which can effectively ensure the coaxiality requirements of the tapered hole relative to the supporting journal and eliminate errors caused by the reference misalignment.
4. Take the taper plug with the center hole as the positioning reference for processing. This method is most commonly used in the outer surface processing of hollow shafts.