April 26, 2024

Brief description of the tooth surface cutting of spur gears


When the differential gear wheel rotates one turn according to the circumference of the table handle shaft, the arc length rotated by the indexing circle circumference of the table workpiece is d/i0=mz/i0; because when designing and manufacturing the gear, the index circle is Calculate the gear size and the reference circle of the split teeth, which is the pitch circle of the cut gear. The distance that the table moves laterally is Pi. According to the nature of the involute, Pi=mz/i0 is known. Because it is an irrational number, a differential double wheel train is used. The feed motion diagram is as shown in the figure. At the time of the insertion, the lateral direction of the table of the inserting bed is fed in the tangential direction of the base circle of the gear, and the circumference of the workpiece of the table is also fed in the circumferential direction, that is, along the tangent BK. scroll. The cutting path of the main motion tool tip K is DKA, which is an involute tooth profile. The cutting process is cut from the crest of the gear to the initial point A of the involute. In order to ensure the correct position of the initial point A of the involute, it is necessary to determine the distance between the lower point K and the point B. The KK radius of curvature k is an involute function of k, which is called the spread angle. Therefore, BK and BOA can be obtained by looking up the table.
Select the machine feed and cut the tooth surface. When the feed rate of the machine tool is constant, the gear ratio is constant, the angular velocity of the table rotation is fixed value, = v / rb, the angular displacement v is AB is equal to the radius of curvature of the lateral movement, that is, v =, the actual feed amount Fv will obtain fv= according to the angular displacement formula and the central angle property of the circle. It can be seen that the actual feed amount fv is a variation, which is in accordance with the involute parameter equation. It can be proved that the quadratic curve is an involute. Therefore, the involute gear shape can be processed by this method. When the indexing device is modified, it must be considered that after the single-tooth processing is completed, the indexing mechanism can be smoothly disengaged from the transmission mechanism to divide the teeth, and then the transmission system can be connected accurately and quickly. In order to facilitate the indexing, the transmission wheel Z1 is integrated with the indexing plate, and is fitted on the circumferential feed shaft with a clearance fit. During the development movement, the transmission wheel Z1 is coupled to the positioning pin through the indexing plate and the handle on the handle to rotate the circumferential feed shaft, thereby driving the table to rotate. When a tooth surface is machined, the table is quickly retracted to the outside of the initial position. Excluding the gap between the drive wheel and the machine itself, the locating pin can be indexed out of the additional drive system. After averaging the corresponding number of holes on the indexing plate, insert the positioning pin into the corresponding hole on the indexing plate and connect it to the additional drive system to perform the cutting process of the next tooth surface until the complete gear is machined. .
Processing example Inspection of gear blanks: mainly to check the size of the tip circle, in order to adjust the cutting depth later, according to the actual crown diameter to increase or decrease, to ensure the correctness of the indexing circle tooth thickness. Then check the perpendicularity of the end face of the tooth blank to the top circle and the hole diameter. Marking: Because the modulus is large, it can't be cut once, and it needs to be processed step by step. Therefore, according to the known conditions, the formula of the involute standard spur gear is calculated: the root circle df=mz-3.5=1250mm The base circle db=dcos=12216mm, the pitch P=m=6283mm, the tooth thickness S=P/2=314mm. The index circle, the root circle and the base circle are drawn on the blank of the gear. The bisector is cut by the number of teeth on the indexing circumference. Taking the bisector as the starting point, the tooth thickness S=314mm and the pitch P=6283mm are taken. According to the formula, R1=bm=2462mm.R2=Cm=Z2sin2/4b=2002mm.R1, R2 is the radius of the toothed arc. Taking the point A as the center and the radius of R1 and R2 as the radius of the gear on the base circle respectively, the approximate drawing method takes two points O1 and O2. With O2 as the center, R2 is the radius of the arc AC and the AB arc is tangent to point A, which is the tooth profile between the indexing circle and the root circle. With r=02 as the root radius, it is tangent to the root circle and the root tooth profile AC. Similarly, draw the approximate tooth profile on the other side. Installation and alignment: The axis of the spur gear coincides with the axis of rotation of the table. The error is within 002mm. And verify the verticality of the working surface and the direction of the knife. Index calculation and adjustment: According to the number of gear teeth given in the figure is 65, the number of machine indexing disc holes is 12065=15565=12226; the number of machine indexing plate holes is 26 holes. Each tooth is equally divided by 22 turns and 22 holes. 22 holes can be adjusted by dividing the indexing fork, eliminating the number of teeth and preventing the indexing error. Socket groove: Use a sharp knife to rough insert the groove width. Leave a margin of about 2 mm for each tooth surface according to the tooth profile. Then use a grooving knife with a blade width smaller than the width of the root groove to cut out the full tooth depth of each tooth groove h=45 mm. Install the attachment to the scale ring on the lateral and circumferential feed axes outside the inserting chute, The parts such as the indexing plate and the connecting body are removed, and the coupling bushings are respectively installed. The transverse bushing is coupled by a key, and the sleeve on the circumferential shaft is not connected to the slide box. One end of the hanging wheel plate is set on the sleeve of the indexing shaft, and three hanging wheel shafts are respectively installed in the three long slots of the hanging wheel frame. The gear z1=65 indexing plate is connected with three M8 screws and then placed on the circumferential bushing, and then the indexing pin and the square end of the handle are mounted. After the hanging wheel key is coupled to the sleeve, it is mounted on the hanging wheel shaft according to the transmission ratio. At the same time, adjust the meshing gap between the gears and lock the hanging axle.

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