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Abstract on the topic of graduation work

Ñontent

Introduction

The development of modern technology makes continuously increasing demands on gears. At the moment, several million different gears are produced in the world. Based on this, the requirements for the quality and productivity of the manufacture of these parts are constantly increasing. Incomplete adhesion of the teeth, increased friction during operation, improper selection of lubricant, deviation of the tooth profile from the involute, wear of the cemented hardened surface layer all this is the cause of wear and subsequent failure of the gear wheels. Most of the causes of rapid gear tooth wear can be eliminated during the gear finishing steps. Therefore, in the production of gears, increased attention should be paid to the finishing of their teeth. To achieve a certain quality, various methods of finishing the gears are used. There are two main ways to cut spur gear teeth: by copying and rolling (bending).

The simplest way to cut by copying is to cut cavities between the teeth with profile (modular) tools. After cutting each depression, the workpiece is rotated by the size of the engagement step. Therefore, this method is also called the division method. n is carried out when cutting teeth with disc and finger cutters, as well as broaches. When using this method to cut cylindrical toothed wheels are usually disc or finger modular cutters. So, we will take a closer look at the copying method when cutting spatially modified teeth of cylindrical wheels with a finger modular cutter.

1. Theme urgency

One of the most pressing tasks today in mechanical engineering is the design and manufacture of competitive machines and units with high performance characteristics. For the proper development of technology and technology, it is necessary to improve the quality, reliability and durability of spur gears. These requirements can be met only by increasing the accuracy of the gears, but this is not economically feasible, or when changing the design of these wheels. In the manufacture of gears, special attention is paid to improving accuracy and productivity.When using multi-axis CNC equipment, it becomes possible to obtain a significant effect of machining gear rims by copying.

The master's work is devoted to the urgent scientific task of developing universal complex types of tooth modifications, observation of the processes occurring during the formation of gear rims.

2. Purpose and objectives of the study, planned results

The aim of the study is to improve the accuracy of manufacturing spatially modified teeth of cylindrical wheels, the gearing on the basis of which are able to compensate for the complex of displacements in case of manufacturing errors, deformation of gear elements during operation by copying a modular finger cutter.

The main objectives of the study:

  1. Analysis of methods for the synthesis of fastenings of cylindrical wheels, which were put into operation in the presence of errors.
  2. Development of a methodology for designing spatially modified gear rims of cylindrical wheels. .
  3. Search and identification of the characteristics of existing elements of technological support to improve the accuracy of multi-axis milling of spatially modified teeth of cylindrical wheels by copying.
  4. Development of theoretical foundations for the control of spatially modified gear rims of cylindrical wheels.
  5. Study of experimental research on cutting gear rims with complex spatial modification of teeth by copying method

    Object of study: parameters of the process of shaping spatially modified teeth of cylindrical wheels

    Subject of study: regularities of the process of forming teeth with a complex spatial geometry.

    As part of the master's work, it is planned to obtain relevant scientific results in the following areas:

    1. Implementation of a spatial approach to solving the problems of shaping cylindrical wheels by gear milling using the copying method.
    2. Analytical determination of the coordinates of points of the spatial trajectory of the relative displacement of the CM, working by the method copying.

    For an experimental assessment of the theoretical results obtained and the formation of the foundation for subsequent research, in practical results is planned to develop the elements of technological support of FKTP for the manufacture of spatially modified cylindrical gear rims wheels for multi-axis gear hobbing by copying with the following properties:

    1. Obtaining and processing of measuring information on technological operations of control of geometric parameters of spatially modified gear rims of cylindrical wheels using digital measuring equipment.
    2. Execution of works on design and technological preparation of production of products with spatially modified gear rims, describe the lateral surface of the tooth with a family of three-dimensional Bezier splines.

    3. Research & Development Overview

    3.1 Requirements for gears

    The following external factors affect the performance of the gearing:

    1. The value of the actual applied force load, since the calculated, nominal load does not lead to a change in the shape of the tooth and does not leave significant traces of deformation on the working surface of the gear train.
    2. The presence of abrasive particles that contribute to abrasive wear or chemicals that cause corrosion of the tooth surfaces, contributing to the occurrence of gas or liquid erosion. The main cause of corrosion - the presence of water in the lubricant - manifests itself as a uniform or uneven layer of rust on the surface of the teeth. Corrosion rates vary.
    3. The degree of mutual movement of the gear wheel relative to the shaft. The immobility of the gear and shaft seating surfaces meets the design requirements if the mating parts remain stationary when a load is applied. The appearance of small displacements of the mating parts leads to fretting corrosion, which manifests itself in the form of dark spots on the fitting surface of the part.
    4. The nature of the interaction of the contacting surfaces, which is determined by the type of friction on the contacting surfaces. If fluid friction prevails, providing a minimum coefficient of friction, and there is a complete separation of the contacting surfaces with a layer of oil, then the condition is assessed as good. In this case, oxidative wear is predominant. The occurrence of boundary friction leads to contact between two parts, manifesting itself in the polishing of the working surfaces of the teeth. Most often, boundary friction occurs at the initial stage of running-in new gears.

      The operating conditions of gear wheels are determined by their speed, the level of contact and bending loads.

    During operation, the teeth of the gear wheels are exposed to[1]:

    1. izgibu pri maksimal'nom odnokratnom nagruzhenii ( pri rezkom tormozhenii, zaklinivanii, pri prilozhenii maksimal'nogo krutyashchego momenta);
    2. izgibu pri mnogokratnykh tsiklicheskikh nagruzkakh, chto privodit k razvitiyu naibol'shikh napryazheniy v korne zuba i ustalostnomu razrusheniyu; bending at the maximum single loading (with sharp braking, jamming, when the maximum torque is applied);
    3. bending under repeated cyclic loads, which leads to the development of the highest stresses in the tooth root and fatigue failure;
    4. contact stresses on the lateral working surfaces of the teeth, leading to the formation of contact-fatigue chipping (pitting);
    5. wear of side surfaces (due to the ingress of abrasive particles, dirt, dust into the contact area), or the end surfaces of the teeth (when shifting gears in gearboxes).

    In this regard, the following requirements are imposed on the teeth of the gear wheels:

    1. high wear resistance of working surfaces;
    2. high efficiency;
    3. noiseless and smooth running;
    4. high kinematic transmission accuracy;
    5. high tooth fatigue strength.

    These requirements can be implemented using thermal, chemical-thermal, finishing, finishing treatment, strengthening by the SPD method. Along with these requirements are attributed the requirements for the accuracy of the gears. Spur gear tolerances are specified in the standard. GOST 1643-81 establishes 12 degrees of accuracy of gear wheels and gears [2]

    ÄFor each degree of accuracy, independent norms of permissible deviations of parameters are established, which determine: kinematic accuracy, smooth operation, contact of teeth in transmission[2].

    Also, GOST 1643-81 established six types of mates that determine the guaranteed side clearance. Side clearance is the distance measured along the normal between the non-working tooth profiles of the mating wheels. The minimum side clearance is required for:

    1. grease placement;
    2. compensation of temperature deformations;
    3. compensation for errors in the manufacture and installation of transmission.

    Gear

    Figure 1 - Gear
    (animation: 8 frames, 65 kilobytes)

    4.Ñonclusions

    The paper considers: the requirements for gears, reasons for failure and a decrease in the operational properties of gears, features of the finishing treatment of the teeth of gears subjected to the application of wear-resistant coatings. The analysis of the considered signs of a decrease in the properties of gears and ways of their elimination is carried out. The goals and objectives of future research are set.

    When writing this essay, the master's work has not yet been completed. Final completion: December 2021. Full text of the work and materials on the topic can be obtained from the author or his manager after that date.

    List of sources

    1. Aleksandrov L. I., Artemenko L. P., Kostiuk D. I. Cogwheels. Kharkov: Kharkov University Press, 1964.276 p.
    2. Barone, Thordion Exact distribution of stresses in standard teeth and geometric coefficients. // Proceedings of the American Society of Mechanical Engineers, Series B, 1973. No. 4. P. 271–176.
    3. Attia The noise of involute helical wheels // Transactions of the American Society of Mechanical Engineers, Series B, 1969. No. 1. P. 179–186.
    4. Adam Ya. I., Antonov OI, Zharkov V.V., Kopf I.A., Ovumyan G.G. Finishing of teeth of large hardened wheels // Vestnik mashinostroeniya, 1980. No. 9
    5. Airapetov E.L., Aparkhov V.I., Melnikova T.N., Filimonova N.I. Uneven distribution of static load in helical and chevron gears // Bulletin of mechanical engineering, 1997. No. 10.
    6. Airapetov E.L., Afonsky B.D., Genkin B.D., Lutsenko V.I., Mdinaradze N.I. On the analysis of the kinematic error of gears with the use of filtration // Vestnik mashinostroeniya, 1985. No. 3.
    7. Baykov A. N., Shraibman S. M. Cutting wheels with a small number of teeth on a gear shaping machine // Bulletin of mechanical engineering, 1973. No. 7.