The design of the wave spring surface requires the wave spring used in the electromagnetic clutch and the brake, and the shape of the curved surface is an important technical parameter affecting the performance of the electromagnetic clutch and the brake. Reasonable selection and design of the wave spring surface is an important prerequisite for the electromagnetic clutch and brake to be sensitive and sensitive, high accuracy, fatigue resistance and long service life, and also affects the wave spring processing process. Therefore, the design requires that the wave spring has no gap between the outer ring of the armature and the inner circle gap of less than 0.1 mm under the condition of flattening under the force, and the gap between the armature and the armature is closely matched to ensure the reliability of the electromagnetic clutch and the brake.
It is known that the structural shape of the wave spring is three waveforms uniformly distributed along the circumference 120. The trough is partially fixed and the crest portion is free. According to the symmetry principle in mechanics, the one-third plane ring is simplified to a mechanical model <3>. At the midpoint of the outer circle of the ring, a concentration equal to the actual load size (about 6.66kg) is applied along the thickness direction of the outer circle of the ring. Load, one end of the third ring is a fixed end, and the network <4> is divided according to the finite element method, as shown in (a). According to this mechanical model, the finite element calculation is performed by American ADINA software, and the displacement of each node of the finite element network is obtained as shown in (b). The curved surface after the force deformation is the actual curved surface after the wave spring is stressed. By using the symmetry principle, the displacement data of each node of the entire wave spring surface can be obtained, and the data required to prepare the design can be processed by the data processing program. Spring forming mold.
The preparation of the surface machining program The surface data calculated by the finite element method is a polar coordinate method. Before programming, the data should first be converted into rectangular coordinate data accepted by the numerical control. It is obviously unrealistic to manually program so much data, the workload is large and the accuracy is not high, and errors are easy to occur, and any errors in actual processing are not allowed. Since the data files acquired by the finite element calculation can be read by the BASIC language, they can be programmed by the BASIC language. Get the NC code of the CNC machine. At the time of preparation, it is processed outwards in a circle by means of processing a full circle until the processing is completed. It can be known from (a) that there are a total of nine 369 (one-third circle) nodes, because the distance between the circles and the circle (2.25 mm) is long between the nodes, and the CNC machine tool is linear interpolation during processing. The machined surface will be very rough and will not meet the process requirements for wave spring forming. Therefore, in order to meet the process requirements of wave spring forming, the existing data must be refined, that is, the radius difference between each circle and the circle is 0.25 mm, and the refinement work can be completed by BASIC language programming. Therefore, two programs before and after data refinement can be obtained. The pre-refinement program can be used as a rough machining program, and the refinement program is used as the final finishing program. These two programs are only the processing procedures of the punch. In the same way, the BASIC language can be used to program, and the processing procedure of the die can be obtained by changing the sign of the Z direction, so that the programming process of the mold is completed, and then the machining of the convex and concave mold can be performed by the numerically controlled machine tool.
The processing method and the data transmission processing method are determined. Because the convex and concave molds are thick and the processing program size is different during finishing, the processing method is different. In the roughing process, the program size is only 36KB, the program can be transferred to the CNC machine tool through the computer once for off-line processing; in the finishing process, the program size is nearly 800KB, which exceeds the memory of the CNC machine tool by 64KB, and the program cannot be transferred to the CNC machine tool at one time. Therefore, it can not be processed offline, and can only be processed online, that is, the upper computer is used to control the numerical control machine tool, and the data is processed while being processed, which is an online processing control mode.
Data transmission mode Data transmission plays a very important role in online processing. Its stability and reliability directly affect the quality of processing. In order to prevent communication errors, the machine tool malfunctions. In the online processing, the point-to-point connection method is adopted, that is, the software and hardware handshake between the PC and the CNC machine tool is realized. <2>. Between the upper computer and the machine tool, through RS232 The serial interface realizes the two-way transmission of data by using the communication software of the PC and the data communication protocol and the DNC function provided by the CNC system to complete the online processing. The transmission process is as follows: the PC opens the communication software, and transfers the program file to be transferred; sets the machine to the DNC mode, that is, first initializes the ports of the CNC and the PC, so that the sending port of the PC and the receiving port of the CNC are in the DNC state. . After communication, the CNC machine takes a program from the PC (such as the first 30KB). When the CNC buffer is full, it feeds back a signal to the PC, and the PC stops sending. While processing, the NC program will be executed. Cache refresh, when the refreshed cache reaches a certain amount (such as 15KB), release a signal to the PC, so that the PC continues to transfer the program to the CNC, and so on repeatedly until the processing program is completed, thus realizing the waveform spring forming surface Online processing.
The processing parameters are determined and processed according to the shape of the blank of the wave spring mold. During roughing and finishing, the process parameters such as the amount of cutting, the feed speed, the depth of the knife and the selection of the tool are different. In roughing, the main purpose is to remove the material and prepare for subsequent finishing. Therefore, it is possible to use ordinary milling cutters for machining. The feed speed and the depth of the knife are larger when the machine allows, saving Processing time, improve efficiency; in the finishing process, the purpose is to ensure the quality and precision, so in order to make the machining surface smooth, the use of spherical milling cutter for machining, the spindle speed is not easy to be too high, the feed speed and the depth of the knife to choose a smaller value The final processed surface fully meets the requirements of wave spring forming.
Conclusion Using the online processing technology, a wave spring forming mold is machined on a simple CNC machine tool. This method opens up a feasible way for automatic programming and processing of free-form surfaces. The effective use of CNC machine tools has been promoted. This method is only suitable for the machining of surface contours and is not suitable for parts with high dimensional accuracy requirements.
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