Manufacturing of narrow retracting spur gear shaft

Figure 1 Slotted gear drive shaft

I. INTRODUCTION Tooth cutting machining can be divided into two types according to its processing principle: profile method and generative method. The profiling method includes the milling of the milling cutters of the module, the forming of the grinding wheel and the drawing of the gears; the method of generating the exhibition includes hobbing, inserting, grinding, grinding and squeezing. Using the above method to process dual gears or gear shafts with large shoulders requires 5 to 10 mm undercuts. However, in some small precision instruments, gear shafts with large shoulders and undercuts of less than 5 mm are sometimes used. As shown in Fig. 1, the gear shaft of the figure has a large diameter shoulder on the left side of the gear ring, and the undercut is only 3.2mm. If it is processed directly by the various tooth cutting methods mentioned above, it may not be possible to use the entire tooth. Cut out the complete tooth profile width, or the shoulder of the tool hit the left side. Therefore, it is necessary to use special processing methods or make certain improvements to the processing methods. The parameters of the gear on the right side of the drive shaft are shown in the table.
Table Gear parameters Number of teeth Modulus Pressure angle Gear teeth Accuracy 12 0.9 20° 9 II. Extrusion gear cold extrusion process is a free-to-roll process in which the squeeze wheel and the workpiece mesh with each other without backlash under certain pressure. The principle of no chip processing, squeeze wheel is a high precision cylindrical gear, can be modified in the tooth height, tooth length direction, and some have a certain amount of displacement. The squeezing wheel moves relative to the workpiece in a parallel line and only moves in a radial direction. During the cold squeezing process, the center distance between the squeezing wheel and the workpiece is gradually reduced until the required size is reached. The characteristic is that the squeezing wheel generates heat during processing. It is small and has no cutting edge, so wear is extremely slow, long life, high production efficiency, the specific processing route of its processing is: rough → car end surface and drilling center hole → car cylindrical surface, chamfering → grooving → in Squeeze teeth on the machine. Gear modification, deburring, third, pinion Among the above methods for machining gears, only the undercut required for the pinion is the smallest, so the pinion cutter can be properly modified to meet the dimensional requirements of the part. . The selection of the pinion cutter Because the left part of the gear has a large shoulder on the left side of the gear, the bowl-shaped pinion cutter is used because the bowl-shaped pinion cutter has a deeper hollow shank to accommodate the fastening screw and can be used for machining. There are obstacle gears below. Since the precision of the gear is required to be 9 grades, a Grade B cutter is used. Since the module of the gear is 0.9, the number of teeth is 12, and the number of teeth is small. In order to avoid the undercut phenomenon, the pinion cutter with the number of cutters z = 12 and the displacement coefficient c cutter = 0.04 are selected. It is best to use an assembly type cutting tool with a mechanical clamping solid carbide blade. Improvements in the use of the two-cutting method for the shaping of the cutting tool To meet the requirements of the narrow undercut, the selected cutting tool must be modified. The easiest way is to reduce the thickness of the pinion cutter. The specific method is to sharpen the anterior horn g to reduce it to about 2° to 3°. However, sharpening of the rake angle will increase the cutting force, which will increase the cutting deformation and sharply increase the amplitude, shorten the service life of the tool, and sometimes cause the tool to collapse. Therefore, it can be considered to divide the gear processing into two. In other words, the required tooth profile is machined on most of the tooth width by using an ordinary pinion cutter (one-slot cutter) first. Then, replace the teeth with a sharpened grind cutter (2nd cutlery) that has been sharpened by the rake. After the tool change, the tool setting problem is to ensure the positioning accuracy of the two insert cutters before and after the tool change, and to avoid the damage to the tooth shape due to the inaccuracy of the tool after the tool change. Therefore, the accuracy of the cutting tool must be guaranteed.

Figure 2 Schematic diagram

The specific method is: Before machining teeth, draw a straight line passing through the axis on the right end face of the gear shaft. (As shown in Fig. 2) Align the tip of any of the No. 1 knife's teeth with the intersection A of the straight line and the outer circle, and then manually test the knife. After replacing the No. 2 knife, let the tip of any of its teeth align with the intersection point A' between the straight line and the tooth root circle. Then try a knife. The length of the stroke length of the pinion cutter is chosen as follows: L=b+y+D Where: b—the width of the ring gear in mm; y—the amount of cut in mm; D— - Cut-out volume in mm. The stroke length of the first pinion cutter is to reduce the wear of the second pinion cutter. To use as much of the pinion cutter as possible to machine the tooth profile on the tooth width, it must be ensured that the pinion cutter will not hit the shaft. shoulder. Therefore, the cut-out amount of the pinion cutter No. 1 was set to 1 mm, the cut-in amount y=7 mm, and the tooth length b=25 mm. So the stroke length of the pinion cutter No. 1 is L=33mm. The length of stroke of the second pinion cutter is smaller because of the rake angle of the second pinion cutter, so the cut-out amount can be larger than that of the first pinion cutter. Here, the cut-out amount D=2.5mm, and the cut-in amount y = 7mm. Therefore, the stroke length of the No. 2 knife is L = 34.5mm. Parts of the process route rough → car end surface, drilling center hole → car cylindrical surface, chamfering → grooving → use one of the pinion cutter teeth → replace the second pinion cutter pin gear → gear repair, deburring. Fourth, the combination of the gear shaft ring gear or left shoulder made removable, and then use the welding method to produce the required drive shaft.

Figure 3 Shaft parts

Figure 4 Gear Shaft Parts

The gears are respectively made of gears and stepped shafts (as shown in Fig. 3), and then the gears are welded on the outer cylindrical surface of the stepped shafts. The shaft shoulder first processes the gear shaft shown in Fig. 4, and then welds the separately processed shaft shoulder to the corresponding position of the gear shaft. V. Conclusion This paper analyzed the difficulties in manufacturing narrow-recessed spur gear shafts. By using special machining methods or improved machining methods, the machining problem of such gear shafts was effectively solved. At the same time, Renshi method also has certain reference significance for the manufacture of multiple gears and gears with shoulders.

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