Design method and parameter optimization of small angle rake face of hourglass worm gear hob

Abstract

In order to improve the cutting performance of the hourglass worm gear hob and improve the cutting conditions of the teeth on both sides, it is necessary to constrain the absolute value of the rake angle of each tooth to be small and control the balance of the rake angles on the left and right sides. Based on the principle of enveloping tooth surface formation (Dong, 1989; Wu, 2009), this paper proposes a method of forming a spiral groove rake face with a variable transmission ratio, so that the rake face of each tooth is formed in segments to achieve the design requirements of small absolute value and balance on both sides. Taking the basic worm speed ω of the hob, the moving speed v of the machine tool cutter, and the installation offset Δx of the cutter as experimental factors, taking the rake angle on both sides of five teeth of the hob as response values, a three-factor three-level response surface analysis method is used to establish mathematical models between each experimental factor and the rake angle on both sides, and analyze the interaction between each factor. The results show that: The order of influence of the three selected factors on the rake angle on both sides is: basic worm speed, machine tool cutter moving speed, cutter installation offset; optimize and obtain the optimal parameter combination for each of five teeth in a spiral groove, perform simulation processing and measure rake angle. The results show that the rake angles on both sides of five teeth are controlled within ±0.3°, which is 94% lower than that when five teeth are processed simultaneously with a fixed transmission ratio. This indicates that rake faces of small rake angle can be designed by optimizing processing parameters, which is conducive to improving and balancing the cutting performance of hobs.

Keywords

• hourglass worm gear hob
• orthogonal test
• parameter optimization
• rake angle
• rake face