Shaft parts is a common type of parts, its structure is a rotating body, the length is generally larger than the diameter, it is widely used in a variety of mechanical equipment, used to support transmission parts, transfer torque and bear load.
The machining of shaft parts should follow certain rules. Through this article, we can understand the specific processing steps and some problems that need to be paid attention to.
I. basic processing route of shaft parts.
The main machining surfaces of shaft parts are outer circular surfaces and common special-shaped surfaces, so appropriate machining methods should be selected according to various precision levels and surface roughness requirements.
Its basic processing route can be summarized into four.
First of all, it is the processing route from rough car to semi-precision car, and then to precision car, which is also the main process route for needle outer circle machining of shaft parts of common materials.
Secondly, from rough turning to semi-finishing turning, and then to rough grinding, fine grinding is adopted. For ferrous metal materials and parts with higher precision, less surface roughness and hardening, this processing route is a good choice. because grinding is its ideal follow-up process.
The third route is from rough car to semi-precision car, and then to precision car and diamond lathe, which is specially used to process non-ferrous metal materials, because the hardness of non-ferrous metal is small and it is easy to plug the gap between sand grains. the required surface roughness can not be easily obtained by grinding, so the processes of precision turning and diamond turning must be adopted.
One kind of processing route is from rough turning to semi-finishing, and then to rough grinding, fine grinding and finishing. This route is a common processing route for ferrous metal materials that have been hardened and require high precision and low surface roughness.
2. Pre-processing of shaft parts.
Before turning the outer circle of shaft parts, some preparation processes should be carried out, which is the pre-machining process of shaft parts.
The important preparation process is straightening.
Because the workpiece blank is often bent in the process of manufacture, transportation and storage.
In order to ensure reliable clamping and uniform distribution of machining allowance, straightening is carried out by various presses or straightening machines in the cold state.
III. Positioning datum for machining shaft parts.
First of all, the center hole of the workpiece is used as the positioning benchmark for machining.
In the machining of shaft parts, the coaxiality of each outer circular surface, taper hole and thread surface and the verticality of the end facing the rotating axis are all important embodiment of the position accuracy.
These surfaces are generally based on the centerline of the shaft, positioning with the central hole, in line with the principle of datum coincidence.
The center hole is not only the positioning benchmark for turning, but also the positioning benchmark and inspection benchmark for other machining processes, which accords with the principle of unified datum.
When two center holes are used for positioning, a number of outer circles and end faces can be machined in one clamping.
Secondly, the outer circle and the center hole are used as the positioning benchmark for machining.
This method effectively overcomes the disadvantage of poor rigidity of the center hole positioning, especially when machining heavy workpieces, the center hole positioning will cause the clamping instability, and the cutting parameters can not be too large.
If you use the outer circle and the center hole as the positioning reference, you don't have to worry about this problem.
In rough machining, the method of using the outer circular surface of the shaft and a central hole as the positioning benchmark can withstand a large cutting torque in the machining, which is a common positioning method for shaft parts.
The third is to take the two outer circular surfaces as the positioning benchmark for machining.
When machining the inner hole of the hollow shaft, the center hole can not 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 machine tool spindle, the two supporting journal is often used as the positioning reference, which can effectively ensure the coaxiality requirement of the cone hole relative to the supporting journal and eliminate the error caused by the non-coincidence of the base.
After that, the cone plug with the central hole is used as the positioning benchmark for machining.
This method is commonly used in the machining of the outer surface of the hollow shaft.
IV. Clamping of shaft parts.
The machining of the cone plug and the cone sleeve mandrel must have high machining precision, and the center hole is not only the positioning benchmark made by itself, but also the reference for the finish machining of the outer circle of the hollow shaft. It is necessary to ensure that the cone surface of the cone plug or cone sleeve mandrel has a high coaxiality with the center hole.
Therefore, when choosing the clamping method, we should pay attention to reduce the installation times of the cone plug as much as possible, so as to reduce the repeated installation error of the parts.
In the actual production, after the cone plug is installed, generally speaking, it will not be removed or replaced in the middle of the processing before the processing is finished.