Construction of machine engagement of gear with tool rack

Introduction

Currently, the manufacture of gears is carried out mainly by two methods: copying and enveloping (rolling). Both of these methods are used in denture and denture. When milling and splitting by the copying method, to remove the part of the material of the workpiece that fills the volume of the future depression, a tool is used (a disc or finger cutter - during milling and a tooth head when splitting) with a cutting contour coinciding with the contours of the recesses of the cut wheel. The contour of the recess of the wheel to be cut is determined by the module m, the number of teeth of the wheel to be cut z and the displacement xm with which the wheel is to be made. With a change in one of these values, the cutting contour of the corresponding tool must be changed, but this is not always possible, and the wheels cut by the copying method are not accurately cut.

In the method of enveloping, interaction on the machine of the cut gear with the tool rack (worm mill, comb) or with the tool wheel (shoulder), which is considered kinematically, is a process of engagement. In this process, the cutting faces of the tooth of the tool occupy all possible enveloping positions with respect to the resulting side surface of the tooth of the wheel being cut. During manufacture, technological movements of the tool are simultaneously carried out, as a result of which material is removed from the recesses of the wheel being cut. The envelope method allows you to produce equally exactly the same wheel tool with any number of teeth. This method is most common.

The production of a gear wheel by enveloping (rolling) is carried out on a machine, and kinematically this process can be considered as the engagement of the producing initial contour of the tool with a cut blank; therefore, this engagement is referred to as machine engagement. The geometry of the gear wheel in this case is determined by the parameters of the producing initial contour (initial contour) of the rack tool and its location in relation to the workpiece when cutting teeth .

Initial contour for cutting teeth of gears is projection of cutting face of tool onto plane perpendicular to axis of blank.

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