Figure 1 shows an arc cam camming for two perpendicular staggered-axis indexing drives. The active cam is a circular-arc rotating body with a contoured ridge. The driven turntable is equipped with several rollers that are evenly distributed along the circumference. When the cam rotates, the contour of the indexing section pushes the roller to index the indexing table; when the cam is turned to the rest section thereof, the two rollers on the turntable cross the ridge of the torus of the cam, so that Turntable stops. As shown in Fig. 1a, the positioning torus is located in the center of the cam, suitable for high speed, light load and small number of occasions. As shown in Fig. 1b, the positioning torus is located at both ends of the cam and is suitable for medium, low speed and medium and heavy load applications where the number of rollers is large. The arc indexing cam is similar to the surface worm with a variable helix angle, and the dial is equivalent to a worm wheel with roller teeth. Therefore, the arc cam also has a single head, multiple heads, and left-handed, right-handed points. The figure shows a single right-hand cambered cam. The relationship between the direction of rotation of the cam and the dial can be determined by a method similar to the worm and worm gear transmission.
1. Process analysis
The arc surface indexing cam is similar to the arc surface worm with a variable helix angle. The turntable is equivalent to a worm gear with roller teeth. Thus, the formation process of the cam contour is equivalent to the two movement processes around the cam axis and the rotation of the axis. There is a certain degree of difficulty in processing. If the cam is machined according to the meshing principle, only two rotary motions are required to complete the machining, but special equipment is required. We are here to discuss the application of machining center technology to complete the processing of arc indexing cam mechanism. Fig. 2 is the cam used in the tool change mechanism of Beijing MYCO's machining center (This worm cam has been batch processed in our horizontal machining center, machine model: ECOCUT 1XZ/TD2, manufacturer: DORRIES SCHARMANN (Germany), CNC system: SINUMERIK 880). From the analysis of Fig. 2, the distance between the center of the turntable and the axis of the cam is 125mm, and the cam radius of the cam surface is R47.5mm. Except for the spiral groove, the workpiece is not complicated. However, considering the processing of the spiral groove, the cam needs to rotate around its own axis, and the axis also needs to oscillate. Therefore, considering the factors such as the interference of the workpiece during the clamping and machining of the workpiece, the workpiece needs to be lengthened and the spiral groove is Processing, clamping using a folder, a top way. According to the pattern, the width of the spiral groove is φ26+0.05+0.03mm, which is divided into two processes. When the rough machining is performed, the keyway milling cutter of φ25mm by SECO (n=400r/min, νf=30mm/min) is used for finishing. At the time, the keyway cutter of the φ26H7 of the company SECO (n=550r/min, νf=20mm/min) was selected. Use oil cooling and lubrication. The process lengthening chart is shown in Figure 3.
(1) The flow chart is shown in Figure 4.
(2) The establishment of the mathematical model is known from the working principle: the cam drives the rotary disk to rotate around the rotary center, and the position of the rotary center is constant. From the processing diagram (see Figure 5) can be seen: M point is equivalent to the center of the rotation (and over the tool center axis), MN is the center distance from the cam to the turntable, after the workpiece is clamped, L is a certain, so that in At any moment, the triangle formed by MN0 is invariable. We can determine the movement trajectory of point M, so as to further obtain the movement trajectory of the tool tip to achieve the purpose of machining the cam. The forming process of the cam profile is formed by the rotation of the workpiece about the B axis and the rotation around the A axis and the movement along the Y axis and the Z axis. Therefore, the machining of the cam needs to be completed by four-axis linkage.
According to the requirements of Figure 6 for analysis:
It can be seen from the requirements of Figure 6 that the cam's rising and falling curves are corrected sine acceleration curves. The equation is:
From the above relationship, the correspondence between α and β can be determined. It can be seen from the processing diagram that the angle β can be determined, and the trajectory of the M point can be determined to obtain the movement trajectory of the tool tip, that is, the Y and Z coordinates of the tool point machining point can be obtained. Finally complete the machining of the cam.
From the processing diagram can be seen:
Tool nose motion path coordinates:
(3) According to the analysis results, the BASIC program BASIC program list is omitted.
(4) Generate NC code From the BASIC program list, it can be seen that three text files, WJP1111.TXT, WJP2222.TXT, and WJP3333.TXT, are generated. These three files are the NC programs of the machining cam (the contents of the NC program list are omitted). (5) Import NC program to the machine The NC program is input to the machine via the machine panel or transmission device. (6) Complete processing.Travel Trailer off road car,Self-Drive Travel Small Trailer,Off-Road Travel Trailer,Tour Trailer for family travel
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