The hypoid gear pair has a complex tooth profile, and its tooth profile quality and dynamic performance have a major impact on its transmission performance. Forming method Hypoid gear large wheel normal tooth profile is straight, and the number of teeth is large; traditional Gleason standard hypoid gear processing machine still uses complex cutter head, cradle and special fixture, measuring tool when processing large wheel Other technologies lead to longer processing preparation adjustment time and lower processing efficiency; and the rigidity of the machine tool is insufficient during the machining process, and the force of the cutter head cannot be excessive. The hypoid gears referred to herein are Gleason systems.

The wide application of numerical control technology in the field of hypoid gear machining has greatly improved the machining efficiency, and the precision and quality of the machined tooth surface are more precise and excellent, thus prolonging the service life and ultimately improving the transmission performance. Therefore, it can be considered to use the finger milling cutter and the indexing head to form and mill the large tooth surface on the vertical CNC machining center, in order to obtain better tooth surface quality and high processing efficiency.

This paper mainly discusses the feasibility of forming and milling of hypoid gears, the establishment of mathematical model of forming milling wheel and the determination of adjustment parameters, the generation of NC machining code and the simulation and experiment of milling.

1 Feasibility analysis of hypoid gear shaping milling 1. The feasibility of quasi-hypoid gear forming milling motion is realized. The tooth surface line of the hypoxial gear of the hypoid gear is part of the arc, and the hypoid gear is formed by a large wheel. When machining, the shape of the tooth surface depends only on the relative position of the cutter head and the wheel blank. When the tooth is cut, the workpiece and the cradle are not rotated, so that the cutter head is directly cut into the wheel blank, and the convex and concave tooth surfaces on both sides of the tooth groove are double-sided. The inner and outer teeth of the cutter head are cut, so that the tooth surface of the large wheel of the forming method is the same as the cross-sectional shape of the cutter blade, and the normal tooth profile is straight.

Therefore, in the numerical control machining, the finger end mill similar to the normal tooth profile can be used to control the movement of the inner and outer blade cones of the simulated cutter head, and the forming method of the hypoid gear large wheel forming and milling can be realized.

1. 2 Feasibility of implementing the test plan Selection of the milling tool Since the material of the hypoid gear is usually alloy steel, the cemented carbide tool can be used to obtain better processing results. The geometry of the finger milling cutter can be determined according to the shape of the machined groove, and the axial dimension of the tool should be small to improve the clamping and processing rigidity.

The selection of cutting machine tools is based on the Cincinnati Arrow 750 vertical machining center. Because the tools, machine tools and fixtures are not stressed during the machining process, the rigidity and thermal stability of the machine can meet the requirements. The specific process parameters (cutting) Speed, feed rate, etc. can be further adjusted according to the processing test conditions.

The selection of the fixture is based on the machining principle of the milling and milling of the quasi-hyperbolic large wheel on the CNC milling machine. The center plane and the horizontal plane are inclined at an appropriate angle to ensure the horizontal plane of the cone of the big wheel. The positioning and clamping are good. The vertical dimension of the head is as small as possible to enhance the rigidity during processing.

2 Determination of milling large wheel adjustment parameters and preparation of numerical control code 2. 1 The establishment of mathematical model of machining, using the finger-type end mill to form the milling machining of the hypoid gear wheel. According to the theory of 1.1, during processing, the large wheel is fixedly connected with the table of the numerical control indexing head and the machining center, and the circular interpolation motion of the table axis and the shaft causes the movement path of the milling cutter relative to the workpiece to simulate the movement of the cutter head, thereby The circular arc groove is milled, the shaft advances and retracts the cutter to cut out the tooth depth, and the large wheel tooth surface is ensured by the tool tooth profile. After machining a tooth profile, the axis of the numerical control indexing head is rotated to index the next tooth.

Establish the coordinate system of the milling machine as shown, and establish the relative position and motion relationship between the tool, the workpiece, the fixture and the machine tool. The machine tool machining coordinate system Oxyz, Ox 2 y 2 z 2 is large and large along the AA direction. The coordinate system of the wheel-fixed joint, where O m is the root cone apex, M is the calculation point, and O 2 O m is the large-wheel coordinate system origin O 2 (the intersection of the large wheel mounting surface and the C-axis) to the root cone apex O m Distance, the origin O of the machining coordinate system is the projection of the origin O 2 of the large wheel coordinate system on the horizontal root cone plane, and OC is the center of the interpolation arc (x Oc, y Oc is its coordinate in the machining coordinate system), m2 is The installation of the root cone angle of the large wheel can determine the starting point A, B of the circular interpolation according to the tooth width.

2. 2 Determination of large wheel installation and cutting tooth adjustment parameters According to the principle of machining the hypoid gear according to the forming method, the difficulty in determining the basic machining adjustment parameters is that the tool tooth pressure angle and the large wheel design root cone pressure angle are different. Rotational pressure angle correction. It has been solved very well and will not be repeated here.

The resulting horizontal location H m and vertical location V m are as follows H m = R 02 cos f 2 cos m - rsin m - h tan m2(1)V m = R 02 cos f 2 sin m + rcos m(2) In the middle, R 02 is the pitch of the section of the production wheel; r and h are the correction amounts; f 2 and m are the helix angles before and after the correction of the calculation point.

From the formula (1), the formula (2), and the m2, O 2 O m, the large wheel mounting position and the cutting tooth adjustment parameters can be determined. In the machining coordinate system Oxyz, the coordinates of the center O c can be obtained as x Oc = V m(3) y Oc = H m - OO m (4) where OO m = O 2 O m cos m2; O 2 O= O 2 O m sin m2. Here is for the big wheel rotation. The coordinates of points A and B can be determined from the center coordinates and the cutter radius r, the coordinates of the calculation point M, and the large tooth surface width b 2 . In this way, the adjustment parameters of the milled hypoid gear can be obtained on the CNC machining center.

2. 3 CNC machining code is compiled based on the specific wheel blank parameters, fixture geometry parameters, tool parameters, combined with CNC milling technology strategy, programming technology, etc., using the program to generate CNC machining code. The current advanced CNC machining technology can meet the requirements of forming milling. Due to the forming of the milling hypoid gear on the four-axis machining center, the final finishing method is circumferential side milling; how to extend the tool while ensuring the machining quality Life expectancy, reduced processing time, optimized process strategy and program processing speed optimization are issues to consider. The specific strategy is to control the feed rate and radial and axial milling depth, optimize the spindle speed, use the appropriate cutting method, optimize the milling parameters, etc., in order to obtain the best tooth surface accuracy and quality and the highest processing efficiency.

3 Example calculation and simulation, processing test using the basic parameters such as the hypoid gear of the large wheel, the forming milling CAD simulation test and the machining center upper milling test, the calculation of the main cutting gear adjustment parameters are: horizontal tool position H m = 28. 4956, vertical tool position V m = 86. 6184, installation root taper angle m2 = 68. 8306, axial wheel position O 2 O m = 54. 6028, the coordinates of the calculation point M in the Oxy plane are xm = 12. 0406, ym = 68. 0283, the coordinates of the center Oc are x Oc = 86. 6184, y Oc = 8. 7704, the coordinates of the starting point A of the arc are x A = - 2. 229, y A = 43. 1093, the coordinates of point B are x B = 42. 0322, y B = 92. 9473. The required adjustment parameters have been obtained.

In order to verify the correctness of the machining model and the NC machining code created in the previous section, according to the above calculations, the solid model of the hypoid gear large wheel was simulated by CAD technology, and then the finger milling cutter was used on the CNC machining center. Fine milling of large wheel blanks to verify the feasibility of CNC machining.

4 Conclusion Under the premise of rapid development of CNC machining technology and forming milling technology, in the vertical CNC machining center, the appropriate tool and fixture can be selected, and the appropriate process plan can be used to realize the forming and milling of the forming hypoid gear wheel. Processing. Its main advantages are: (1) It can expand the application range of the machining center and reduce the dependence on the special machine tools and tools for gear processing. (2) It can process large wheels with large size and wide tooth surface, and abandon the processing limitations of special machine tools. (3) Improve the processing efficiency of the forming hypoid gear, improve the tooth surface quality, and improve the transmission performance.

(Finish)

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