When the first trial is cut, it is designed as a tooth with an antenna. Referring to the tool design manual, the tooth profile of the hob is as follows: the tooth side is formed by two straight lines with tooth angles of 20 and 30 respectively, the top of the tooth is divided into a small antennae, and the thickness of the antenna is 0.080.10 mm. The top is a flat top with two small arcs of R0.5mm. However, the results of the trial cutting show that the gears with the angle hob can not meet the requirements of use, mainly because the tooth edge trimming amount a, b is too large, the root root cutting arc is too long, the effective involute starting point Excessively cut off, so some gears appear broken during the gearbox test phase. In addition, due to the fact that the effective meshing involute portion is too short, some gears are vibrated and the noise is excessive. For gears with a small number of teeth, such as the intermediate shaft (m = 3mm, z = 13) and the first speed gear (m = 3mm, z = 40), if the gear is processed with a tenter with a tentacles, it cannot be achieved. It can ensure that the starting point of the effective involute is not cut off, and it can ensure the effect of a certain amount of sinking at the root of the gear. Therefore, it is an important subject of gearbox gear processing to optimize the design of the front profile of the shaving hob and improve the trimming and undercutting of the rear tooth profile.
In the subsequent tests, we have adopted methods such as reducing the height of the antennae, reducing the height of the crown, and increasing the radius of the crown of the tooth, but they have not achieved the desired effect, and the processing and repair rate is still high.
Finally, we tried a pre-shave hob with no tentacles and corrected the effective crest height parameters. At this time, the tooth profile is characterized in that the tooth side is composed of three straight lines with tooth angles of 15, 20, and 3233, respectively. The tooth top is a single arc dome and is tangential to 15 lines, and the root is 0.3 mm. . The gears machined by this toothed hob have a satisfactory effect, and the root of the tooth produces a micro-root cut, which ensures the sharpening of the sharpening knife tip, and also ensures that the starting point of the effective involute is not removed. However, the calculation of gears or hobs is cumbersome when using this design method. To this end, we applied a computer-aided calculation program to calculate the normal tooth shape and axial tooth shape of the hob, and then converted it into the tooth profile of the gear, and simulated the cutting using computer-aided drafting technology (CAD). The tool path in the process of machining, drawing the envelope pattern corresponding to various parameters, provides a reliable theoretical basis for tool tooth shape design. From the results of the trial cut, the trimming and sinking conditions are in line with the shaving front tooth shape, and the root strength tends to be reasonable.
(1) Tip height According to the literature, the height of the tip is determined by two parameters: modulus m and tip height coefficient. The most common shaving hob tip height is 1.35 m. There are several pairs of gears in the gearbox ( In particular, when the number of teeth of the conjugate gear is large, we have made some corrections to the height of the tooth tip, which may be increased or decreased on the basis of 1.35m to ensure the meshing length of the effective involute.
(2) The top of the tooth is generally a small arc with a flat top with a flat top. The gearbox gear used in our factory requires the root of the tooth to be a single arc to avoid stress concentration of the root and cause broken teeth. However, the root of the gear that is usually machined by the pre-shave hob can not form a single arc, and the amount of undercut is too long and too deep, which is the main cause of the broken tooth. According to this situation, a single circular arc of the hob tip which is slightly smaller than the gear tooth root arc (about 0.45 mm) is used. The large arc is used instead of the original flat top and two small arcs of the shaving hob to cut the bottom curve of the tooth bottom smoothly, without stress concentration points, and the root strength is improved.
(3) The middle part of the cutter tooth side is generally designed with a thickened antennae. The purpose is to cut a small circular arc on the root side with the antennae to facilitate the shaving of the knife (equivalent to micro root cutting). ). However, for gears with few teeth, the original undercut phenomenon has been more serious. For example, if the angle of the root of the gear is too large, the effective involute length is too short, which will seriously affect the meshing quality. In response to this situation, we adopted a non-antennat tooth profile, which consists of three straight lines of 15, 20, and 3233 to form the tooth side, of which 20 straight part is tangentially effective involute meshing part; 3233 linear part is hobbing gear tooth top Trimming part; 15 straight line and the top of the toothed part of the toothed part of the tooth cutting arc and the undercut part. The cutting trajectories of each part are designed as required. The gear shaving hob designed by the above method can effectively solve the processing problem that cannot be solved with the tentacles before the shaving.
When the effective involute starting point F is close to the base circle, the tooth shape cut by the shaving hob is as shown by the thick solid line, and the shaving tooth shape of the shaving cutter is shown by the dotted line, and the shaving cutter blade basically falls on the top. The maximum point of the circular arc, the shaved tooth shape does not appear or only a small amount of undercut phenomenon, can better meet the use requirements.
In the subsequent tests, we have adopted methods such as reducing the height of the antennae, reducing the height of the crown, and increasing the radius of the crown of the tooth, but they have not achieved the desired effect, and the processing and repair rate is still high.
Finally, we tried a pre-shave hob with no tentacles and corrected the effective crest height parameters. At this time, the tooth profile is characterized in that the tooth side is composed of three straight lines with tooth angles of 15, 20, and 3233, respectively. The tooth top is a single arc dome and is tangential to 15 lines, and the root is 0.3 mm. . The gears machined by this toothed hob have a satisfactory effect, and the root of the tooth produces a micro-root cut, which ensures the sharpening of the sharpening knife tip, and also ensures that the starting point of the effective involute is not removed. However, the calculation of gears or hobs is cumbersome when using this design method. To this end, we applied a computer-aided calculation program to calculate the normal tooth shape and axial tooth shape of the hob, and then converted it into the tooth profile of the gear, and simulated the cutting using computer-aided drafting technology (CAD). The tool path in the process of machining, drawing the envelope pattern corresponding to various parameters, provides a reliable theoretical basis for tool tooth shape design. From the results of the trial cut, the trimming and sinking conditions are in line with the shaving front tooth shape, and the root strength tends to be reasonable.
(1) Tip height According to the literature, the height of the tip is determined by two parameters: modulus m and tip height coefficient. The most common shaving hob tip height is 1.35 m. There are several pairs of gears in the gearbox ( In particular, when the number of teeth of the conjugate gear is large, we have made some corrections to the height of the tooth tip, which may be increased or decreased on the basis of 1.35m to ensure the meshing length of the effective involute.
(2) The top of the tooth is generally a small arc with a flat top with a flat top. The gearbox gear used in our factory requires the root of the tooth to be a single arc to avoid stress concentration of the root and cause broken teeth. However, the root of the gear that is usually machined by the pre-shave hob can not form a single arc, and the amount of undercut is too long and too deep, which is the main cause of the broken tooth. According to this situation, a single circular arc of the hob tip which is slightly smaller than the gear tooth root arc (about 0.45 mm) is used. The large arc is used instead of the original flat top and two small arcs of the shaving hob to cut the bottom curve of the tooth bottom smoothly, without stress concentration points, and the root strength is improved.
(3) The middle part of the cutter tooth side is generally designed with a thickened antennae. The purpose is to cut a small circular arc on the root side with the antennae to facilitate the shaving of the knife (equivalent to micro root cutting). ). However, for gears with few teeth, the original undercut phenomenon has been more serious. For example, if the angle of the root of the gear is too large, the effective involute length is too short, which will seriously affect the meshing quality. In response to this situation, we adopted a non-antennat tooth profile, which consists of three straight lines of 15, 20, and 3233 to form the tooth side, of which 20 straight part is tangentially effective involute meshing part; 3233 linear part is hobbing gear tooth top Trimming part; 15 straight line and the top of the toothed part of the toothed part of the tooth cutting arc and the undercut part. The cutting trajectories of each part are designed as required. The gear shaving hob designed by the above method can effectively solve the processing problem that cannot be solved with the tentacles before the shaving.
When the effective involute starting point F is close to the base circle, the tooth shape cut by the shaving hob is as shown by the thick solid line, and the shaving tooth shape of the shaving cutter is shown by the dotted line, and the shaving cutter blade basically falls on the top. The maximum point of the circular arc, the shaved tooth shape does not appear or only a small amount of undercut phenomenon, can better meet the use requirements.
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