Globoid Worm Research Articles

Increasing the operational parameters of worm gears

An analysis of factors that reduce the operational parameters of worm gearboxes has been carried out. Equations for calculating the efficiency of a worm gear, contact pressure, and the residual service life are given. It is shown that the friction angle and friction coefficient depend on the material of the worm and wheel teeth, the roughness of the working surfaces of the worm pair matings, the quality of the lubrication, and the sliding speed. Significant contact pressures and friction losses in meshing lead to heat generation, a decrease in efficiency and service life of the worm gear. To produce a worm gear with a maximum radius of a conjugate globoid-cylindrical pair with an involute profile, it is proposed to use rotational turning of the globoid worm turns with a multi-blade forcedly rotating tool, and the wheel teeth with a hob cutter. A nickel antifriction solid lubricating coating containing carbon nanotubes has increased hardness and resistance to abrasion. A method for manufacturing a ZT-type worm gear is proposed, as well as methods that reduce contact stresses and the coefficient of friction during operation of a mating worm pair to increase the service life of worm gears.

ПОВЫШЕНИЕ НАГРУЗОЧНОЙ СПОСОБНОСТИ МЕЛКОМОДУЛЬНОЙ ЧЕРВЯЧНОЙ ПЕРЕДАЧИ

The study objective is to analyze possible ways to increase the load capacity and develop a worm gear that meets the following requirements and working conditions: minimum weight, high reliability, maintenance-free, short-term operation mode, limited lubrication conditions, the ability to work at low temperatures. The task to which the paper is devoted is to increase the load capacity and the wear resistance of worm gears. The load capacity is defined as the possibility of transmitting the greatest torques with the smallest overall dimensions. The research methods are based on the theory of strength, theory of elasticity, mechanics of contact interaction. The novelty of the work is in finding effective design and technological ways to increase the load capacity, developing a modification of the worm gear and testing the method for calculating the strength of the transmission with a globoidal worm.
 Research results: a review and analysis of the results of studies concerning the modification of gear, working conditions, lubrication, manufacturing technology, wear; possible methods of increasing the bearing capacity of a small-module worm gear are considered; a modification of the gear with a globoidal worm is developed; a method of strength calculation is tested.
 Conclusions: the method of strength calculation and the method of modification of the globoidal gear allow improving the quality characteristics of worm gears – weight and size characteristics, reliability, resource, ease of operation.

Design of gripping devices based on a globoid transmission for a robotic biomaterial aliquoting system

AbstractEvery year the shortage of biosamples is increasing, while the requirements for their quality are constantly tightening, which requires the introduction of new technological solutions. To solve these problems, a robotic system for aliquoting biological liquid was developed. The aliquotation process is described. The station includes a serial robot on which a gripper based on a globoid worm is installed. The gripping device is parameterized and takes into account the gripping force for different finger deflections. 3D models were developed using Computer Aided Design (CAD) system tools, after which working layouts were created using 3D printing. The design process and test results are discussed to show the efficiency of the built prototype with lab tests.

Globoid-bevel gear with intersecting axes

A new type of gearing with intersecting axes is proposed, which combines a modified globoid worm (driving link) and a bevel driven gear, the teeth of which are located on a cone with a generatrix, which is an arc of a circle. The ratios of the parameters of the proposed transmission are obtained, recommendations for its application are given. Keywords: globoid-bevel gear, modified globoid worm, initial cone, taper condition, engagement parameters. shevchenko6-32@yandex.ru, mukhovatiy@mail.ru, krolos@yandex.ru

Методика расчета на прочность глобоидной червячной передачи

Worm gears are widely used in mechanical engineering. Recently, worm gears with a globoid worm attract a considerable interest. To improve the quality characteristics of globoid gears, their geometric dimensions and parameters, as well as the production technologies are being improved. It is also important to have a methodology for calculating the strength, which is, however, currently unavailable, and the state standards cover the issue of determining and calculating only the transmission geometry. In this regard, the development of the technique for calculating the contact and bending strength of a globoid worm gear appears relevant. The basic areas of the research are gear enhancement, production technology improvement, the gearing pattern study, working surfaces mathematical simulation, 3-D modeling, and the transmission calculation. The contact strength calculation is based on the Hertz’s formula taking into account the geometric features of globoid worm gears. The authors developed the calculation of the bending strength of the worm gear teeth based on the helical gear calculation method. The paper presents data on the influence of the mechanical properties of the materials of a worm and a worm gear wheel on the gear contact strength, gives the computed coefficients estimated values. The authors note that the dynamic load factor can increase significantly with the wear of the gear working surfaces. The research findings can be used to develop the design calculation technique, as well as to improve it to take into account the effect of transmission wear and working temperature on the operation duration.

Determination of contact pattern for double enveloping worm gear

Abstract The paper presents the method of determining geometric contact pattern by using the direct computer-aided design (CAD) method for ideal globoid worm gear in which mounting deviations are considered. The tooth contact analysis was performed for all cycle of worm rotation. Based on the results of temporary contact pattern, graphical characteristics of the contact area size depending on worm position were made. A complete analysis of the correctness of gear meshing can be obtained based on presented method. If the worm or worm wheel is incorrectly designed in terms of the geometry, the meshing simulation of CAD models can indicate the collision. Geometric contact pattern analyses were made at two pressure angles of ideal gear. The analysis of the influence of mounting deviations was done against one selected pressure angle and one gear position.

Analysis of the geometry and contact density of globoid gearing

Globoid worm gears have been widely applied in a range of technological branches in which other types of worm gears are less effective. The main functional indicators which facilitated their popularity include high load capacity and durability, low vibroactivity and small energy losses. As the experience of application and the results of the study of globoid worm gears showed, the level of operational properties of globoid gears is higher than that of the others only if the gearing and technological parameters of their manufacturing are optimally chosen during the design stage. This paper describes a method for estimating the gearing parameters of a globoid gear with an account of the geometry of the elements (the geometry of the teeth of the wheel and the worm thread), namely the calculation of the gap fields in the globoid gearing by means of numerical methods.

Globoid surface shaped with turning and envelope method

In industrial practice, cylindrical worm gears are most often used due to their feasibility. In the literature, much attention has been paid to determining the helical surface of worms of such transmissions. Globoidal worm gearboxes are much less frequently used due to technological difficulties. Come on, the globoidal worm ensures simultaneous cooperation of a larger number of teeth and the location of the teeth contact line is more favorable. Therefore, the following is an analytical method for the description of a globoid surface by turning and by a finger milling method.

Simulation of globoid worm gear cutting by continuous forming method with disk milling cutters

Simulation of globoid worm gear cutting by continuous forming method with disk milling cutters

New technology for manufacturing quasi-globoid worm gearings

The advantage of the globoid worm gearing, that all teeth of the worm are in mesh in every moment, is well-known. The main advantage of the helical worm gearing, the easy production is also known. The paper presents a new gearing construction that tries to combine these two characteristics in one novel worm gearing. This solution, similarly to the manufacturing of helical worm, applies turning machine instead of the special teething machine of globoid worm, but the path of the cutting edge is not parallel to the axis of the worm but has an angle in the vertical plane. The resulted in form is a hyperbolic surface of revolution that is very close to the hourglass-form of a globoid worm. The worm wheel then generated by this quasi-globoid worm. The paper introduces the geometric arrangements of this new worm generating method then investigates the meshing characteristics of such gearings for different worm profiles. The considered profiles are circular and elliptic. The meshing curves are generated and compared. For the modelling of the new gearing and performing the meshing analysis the Surface Constructor 3D surface generator and motion simulator software application was used.

The direct solid method of geometry analysis of the globoidal worm gear with the rotary teeth

The tooth contact analysis (TCA) in the wheel rotation function of the globoidal worm gear with rotary teeth was presented. To determine the contact in CAD system, the direct solid method of geometry analysis was used. In the gear the globoidal worm gear was used, and the classical worm wheel was replaced by the wheel with rotary teeth in the shape of the frustum of cone.

Analiza śladu styku zębów w przekładni ślimakowej globoidalnej w środowisku CAD

Presented is the method of determining the contact pattern in globoidal worm gear using CAD environment. Contact pattern analysis was performed for the gear with straight tooth profile in the central plane. The influence of the pressure angle on the shape and size of the contact pattern was investigated.

Mathematical description of tooth flank surface of globoidal worm gear with straight axial tooth profile

AbstractIn this article, a mathematical description of tooth flank surface of the globoidal worm and worm wheel generated by the hourglass worm hob with straight tooth axial profile is presented. The kinematic system of globoidal worm gear is shown. The equation of globoid helix and tooth axial profile of worm is derived to determine worm tooth surface. Based on the equation of meshing the contact lines are obtained. The mathematical description of globoidal worm wheel tooth flank is performed on the basis of contact lines and generating the tooth side by the extreme cutting edge of worm hob. The presented mathematical model of tooth flank of TA worm and worm wheel can be used e.g. to analyse the contact pattern of the gear.

Programming While Construction of Engineering 3D Models of Complex Geometry

The capabilities of geometrically accurate computational 3D models construction with the use of programming are presented. The construction of models of an architectural arch and a glo-boid worm gear is considered as an example. The models are designed in the AutoCAD pack-age. Three programs of construction are given. The first program is for designing a multi-section architectural arch. The control of the arch’s geometry by impacting its main parameters is shown. The second program is for designing and studying the working surface of a globoid gear’s worm. The article shows how to make the animation for this surface’s formation. The third program is for formation of a worm gear cavity surface. The cavity formation dynamics is studied. The programs are written in the AutoLisp programming language. The program texts are provided.

Compound modification of globoidal worm drive with variable parameters

• Propose a meshing theory for a globoidal worm drive under modification with variable parameters. • Establish a mathematical model for meshing analysis. • Study the meshing geometry theoretically and numerically. • Implement comparative researches on meshing properties among diverse drive types. • Discover some drive types have favorable performance during meshing. The meshing theory is built for the globoidal worm drive systematically. Several modification parameters, including the center distance, the transmitting ratio and the height of the cutter frame, are taken into account concurrently and they are all variable. Many types of modification in the foregoing study can be viewed as the special cases of this work. A new method is proposed to obtain the velocity ratio modification function. The height modification function is recommended to adopt a linear function, whose coefficients may be determined by the trial method. The meshing function of the worm pair is deduced by virtue of the vector rotation approach. In the case of the modification with single constant parameter, the classification standard of the drive type is proved strictly. The computing methods of the contact zone, the contact line, and the instantaneous meshing point are expounded explicitly. The reason why a globoidal worm drive can implement the double-line contact between the teeth is uncovered clearly. The reason why a modified globoidal worm gearing can shun the curvature interference is discovered. The comparative researches on the mesh characters of the diverse modified drives are implemented adequately. Some kinds of the modified drive, containing the compound modified drive with variable parameters, are recommended to be utilized in practice for the excellent mesh performances.

Matematyczny model boku zęba ślimacznicy przekładni ślimakowej globoidalnej

Presented is a mathematical description of tooth flank surface of the wormwheel in globoid worm gear. The kinematic system of tooth formation was performed. The mathematical description of tooth flank of globoid worm was used.

Matematyczny model ślimaka globoidalnego o wklęsłym i wypukłym zarysie zęba

This paper presents a mathematical model of globoid worm with concave and convex tooth profile. The method of creating the parametric equation of the profile was shown. The parametric equation of teeth surfaces of globoid worm with nostraight tooth profile was obtained.

Mathematical model of tooth flank of worm wheel with arc profile in globoid worm gear

Mathematical model of tooth flank of worm wheel with arc profile in globoid worm gear

Load distribution in the worm meshing

The paper presents a theoretical analysis of deflections of circular and rectangular cantilever plates of an elastically built-in edge. The problem has been solved using the finite difference method. A method of determination of load distribution between two plates being in contact along an arbitrary line has been presented. Different shapes of these plates constitute models of mating of cylindrical and globoidal worm meshings. To verify the presented theory of searching for load distributions along the contact lines in these meshings, experimental investigations with the freezing of stresses in the cylindrical worm meshing have been carried out. Directions of investigations that would specify further theoretical considerations over load distribution in globoidal gear meshings have been indicated.

The methods of globoid surface modeling in CAD

Purpose: Modeling of globoid worm surface is a difficult issue of modeling of complexsurfaces in CAD. Worm gears are a challenge for designers because of the constructionand the functions that have to be met, as well. There are very few specializedapplications to generate this type of gears. The software intended to model of the wormgear wheel only is not accessible, so basing on general intending CAD systems is anecessity. Modeling of globoid worm surface can cause the problem. The examplesof globoid helical surfaces modeling in CAD are accessible on the Internet, but oftenthey are not correct in terms of geometry and they do not reflect the actual geometry.These surfaces are modeled on the helix with uniform pitch but diameter variable only.The worm gear development, including these atypical ones, requires looking for newsolutions in their modeling.Design/methodology/approach: The three methods of the globoid surface modeling,using CAD systems - AutoCAD and CATIA were presented. The modeling was carriedout on the example of the warm lateral surface of the globoidal worm gears. In thefirst presented method the external program, that generates the script commands forAutoCAD system and lets generate the points of the globoid helix, was used. In thefollowing two methods to model helixes, the possibilities of CATIA were used: creatingthe graph of two-dimension functions and comprising them into tree-dimension functionand kinematic simulation, as well. In the globoid helix the pitch variation is included.Findings: The described methodologies are universal and allow to generate the globoidlateral-surface of worm on the basis of wormwheel constructional assumption andtaken tooth profile. The advantages of CAD systems and their usefulness in the globoidworm gear designing are highlighted in the article.Research limitations/implications: The main problem concerned the method No.3 that uses a kinematic simulation of CATIA. The number of simulation “frame” is thelimitation.Practical implications: The proper modeling of worm gear geometry in CAD allows toanalyse the geometric cooperation, strength (by the finite element method), or to makea prototype for the preliminary tests with using of the rapid prototyping techniques.Originality/value: All three presented methods are innovative and allow to provide acorrectly modeled globoid surface as a basis to create a complete model of the globoidworm.