New possibilities of worm thread machining and practice of implementation

Evgenii S Trubachev ,K V Bogdanov

doi:10.1051/matecconf/202031705003

Evgenii S Trubachev , K V Bogdanov

Open Access

https://doi.org/10.1051/matecconf/202031705003

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Abstract

Thread grinding is the traditional operation of final machining for worms and other critical threads. However, similar to other types of tooth grinding, this type of machining is expensive; it requires application of high cost equipment and needs valuable workers. In many practical cases, its alternative can be the application of edge machining, especially as the possibilities of controlling the corresponding advanced machine-tools and their accuracy have been increased significantly. This paper describes the experience of implementation of edge machining of worm threads within a low-series production of spiroid and worm gearboxes for pipeline valves gained at the Institute of Mechanics named after prof. V.I. Goldfarb of Kalashnikov Izhevsk State Technical University and at the Small Innovative Enterprise “Mechanik”. Schemes of thread machining by straight and radial parts of a single cutter and by a face cutter head are considered. The technique is implemented, and it provides the reduction of labor intensity and prime cost of both the preliminary and final machining of worms, including heat-strengthened ones; and it also results in the correctly localized contact in worm and spiroid gears.

Highlights

Machining operations for teeth and turns of threads are strongly determining the labor intensity and quality of machines, that is why, improvement of tooth machining is traditionally an urgent issue [1]
Grinding operations are performed at the high precision and expensive equipment provided with all necessary devices for fine correction of parameters – height, thickness, angles and radii of thread profiles
There is a successful practice of machining surfaces as well as tooth surfaces by hardalloy tools [2, 3, 4], but the limiting factor for finishing edge machining of threads is the absence of fine adjustment for parameters of machined helical surfaces within a standard layout of these machine-tools, and rigid linkage of the obtained thread profile with the geometry of a tool and its mounting which complicates the setting and resetting of the equipment

Summary

Introduction

Machining operations for teeth and turns of threads are strongly determining the labor intensity and quality of machines, that is why, improvement of tooth machining is traditionally an urgent issue [1]. Grinding operations are performed at the high precision and expensive equipment provided with all necessary devices for fine correction of parameters – height, thickness, angles and radii of thread profiles. The employment market provides a sufficient (and even increasing) number of operators for CNC machine-tools (lathes, grinding and boring ones and other) and even centers of their training. It is common that possibilities of thread and worm grinding machine-tools are abundant for machined worms and threads (even rather critical, though non-precision ones); it becomes clear that it is exciting for a manufacturer to master machining of threads (including heat-strengthened ones up to HRC 50...60) by CNC thread cutting lathes.

Controlled thread parameters and traditional methods of control

Thread profile is generated by a rectilinear cutting edge of the cutter

Thread profile is generated by a circular cutting edge of the cutter

Thread profile is generated by a face cutter head

Prospects of implementation of the new scheme of worm thread machining

Conclusion