CNC Manufacturing Of Circular Faced Cylindrical Gears

Figure 1 21x35 contact pattern simulation

Spurved gears are essentially spur gears generated using a face mill cutter. Spurved gears can theoretically be cut on conventional spiral-bevel gear generators and multi-axis CNC machines.

Because of their convexo-concave contact in the face-width direction, spurved gears offer strength and contact characteristics, making them interesting for certain parallel shaft applications where increased tooth bending stiffness is required.

In order to illustrate the method, two spurved gear sets, m = 1.352 mm, were designed with the parameters listed in Tables 1 and 2. The spurved sets were manufactured on a 5-axis CNC machine. Figures 1 and 3 show the predicted contact patterns on the gear, and Figures 2 and 4 show the actual contact patterns obtained on the VH tester.

Figure 1 21x35 contact pattern simulation

Figure 2 21x35 actual contact pattern.

Figure 3 41x41 contactpattern simulation.

Figure 4 41×41 actual contact pattern.

Figures 1 to 4 show the excellent agreement between the simulation and the actual contact patterns. Figure 5 shows the CMM output, for the Z1 = 41 pinion. Slight pressure angle error can be seen on the convex flank, which can easily be corrected by closed loop.

Figure 5 CMM output: Z1 = 41.

The term “spurved gears” refers to spur gears with a curved face cut using a face mill cutter. In this paper, a general method is presented to design, analyze and manufacture spurved gears on a 5-axis CNC machine. Cutter tilt is used to control the size of the contact pattern, and modified roll is used to control trans- mission error. When the Ease Off and size of the contact pattern are comparable, spur and spurved gears behave in a similar way when subjected to the same center distance and misalignment errors. However, because of their circular face, spurved gears are expected to be stiffer than spur gears, and thereby may offer an advantage where sudden torque is applied. Examples show that model prediction for contact pattern shape and location correlate very well with that of actual parts.