Functionally-oriented technology for backing-off of new standard gear-cutting hobs

The results of scientific research of production technology aimed at identifying predictable errors and ensuring the required quality of processing are presented.

Profiling of a shaped worm cutter for shaping gears with non-involute tooth profile

Of the mechanical transmissions used in mechanical engineering, the most common are gears with an involute profile of the teeth flanks. Gears made up of such wheels have a number of advantages, but they also have a number of significant disadvantages. Therefore jne of the current trends is the study of gears with a complex non-involute profile of the teeth flank which have advantages over involute gears in a number of applications, as well as the development of tools for their processing. There are two ways of gear teeth cutting: the copying method and the rolling-in method. The rolling-in method has advantages. The profile of the tool working by the rolling-in method does not depend on the number of teeth of the gear being cut, therefore, the same tool can be used to cut gears with any number of teeth. The accuracy of a gear made by the rolling-in method is significantly higher than the accuracy of a gear made by the copying method. This is primarily due to the continuity of the rolling-in process. When cutting teeth by the rolling method, the tooth surface is formed as a result of processing with a tool, the cutting edges of which are the tooth profile of the mating rack or the tooth profile of the mating gear, and during processing the tool and the workpiece form a mating gear pair. The most common gear cutting tool is the hob cutter. For the machining of gear wheels with a non-involute tooth profile widely used in industry equipment is used. One of the options for a rolling gear cutting tool for shaping gear wheels with a non-involute tooth profile can be a shaped worm cutter. The article describes the method of profiling of the cutting part of shaped hob cutter for machining of gear wheels with normal accuracy. To solve the problem the unified mathematical base – the apparatus of multiparameter mappings of space – the unified structure of mappings for gears and a compact set of unified operators, parameters and functional connections is used.

PECULIARITIES OF THE PROCESS OF ULTRASONIC VIBRATION MASHINING

The paper discusses the distinctive features of the machining process during low-module gear cutting with ultrasonic vibration of the blank.

Calculation of the Digital Prototype for Modification of the Initial Straight Profile to the Form of the Tooth-Cutting Tool’s Producing Surface

Spatial helical gears, worm gears with a cylindrical worm, globoid gears, etc., are widely used in most of modern engineering products [1-3; 37; 42]. Cylindrical worm gears are actively used in the creation of metalworking equipment (push mechanisms of rolling mills, presses, etc.), in lifting and transport machines, in drives and kinematic chains of various machine tool equipment where high kinematic accuracy is required (dividing machine tools, adjustment mechanisms), etc. In a worm gear a cylindrical worm or its cylindrical helical surface can be cut by various technological methods [49-51], but no matter how the shaping of the worm gear elements’ working surfaces is carried out, the worm wheel is cut with a gear cutting tool, whose producing surface coincides with the worm thread’s lateral surface [19; 22; 23]. In this regard, the working surface of the cylindrical worm wheel’s tooth, even with a non-orthogonal arrangement of axes, is an envelope of a one-parameter family of surfaces that gives a linear contact, which presence makes it possible to transfer a large load using a worm gear. For high-quality manufacturing of worm gears, it is necessary to design and manufacture a productive gear cutting tool - an accurate worm cutter, whose shaping (working) surface must be identical to the profiled worm’s shaping (working) surface [24-27; 54]. One of the most important tasks in the implementation of worm gearing is the problem of jamming of the cylindrical worm and the worm wheel’ contacting surfaces. This problem is excluded by relieving the contacting surfaces’ profile along the contact line. Considering that any violations of contacting surfaces’ geometric parameters affect the change in their geometric characteristics, the tasks of accurately determining the adjustment parameters of the technological equipment, used for shaping the worm and worm wheel, enter into in the foreground of the worm gearing elements production. In modern conditions of plant and equipment obsolescence, and in particular, of gear cutting machines used for worm gears manufacture, these machines physical wear, implies an inevitable decrease in the accuracy of their kinematic chains. Therefore, in order to maintain the produced gears’ quality at a sufficiently high level, it is necessary to use deliberate modification of contacting surfaces when calculating the worm gearing’s geometric parameters; such modification reduces the worm gear sensitivity to manufacturing and mounting errors of its elements [28-31].

Technique of Tooth Relieving for Gear Cutting Hobs

Затылованная поверхность боковой стороны зубьев червячной фрезы - это аналог винтовой поверхности с углом подъема, увеличенным для одной и уменьшенным для другой стороны зуба относительно угла подъема производящей поверхности. Основные недостатки действующей технологии затылования: искажение профиля производящей поверхности в ходе переточек фрез для восстановления режущих свойств инструмента, зависимость наладки процесса затылования от диаметра шлифовального круга и высокая трудоемкость достижения требуемой точности профиля производящей рейки фрезы.Предложено изготавливать боковые поверхности зубьев фрезы как эвольвентные, так как теоретически точная эвольвентная винтовая поверхность может быть получена шлифованием при параллельных осях шлифовального круга c прямолинейным профилем и шлифуемого изделия. Приведен порядок расчета параметров фрезы и процесса затылования. Разработана методика расчета органической погрешности получаемого профиля производящей рейки фрезы. Определен основной параметр предварительного затылования фрезы – спад затылка зуба на угловом шаге фрезы в зависимости от длины шлифованной части зуба и припуска на шлифование. Исследованы и определены параметры фрезы и процесса затылования, исключающие недопрофилирование затылуемых поверхностей. Приведены примеры расчетов применительно к изготовлению прецизионных фрез класса точности ААА.