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Double enveloping worm gear modelling using CAD environment

Połowniak Piotr, Sobolak Mariusz, Marciniec Adam

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2021

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Vol. 69, nr 2

art. no. e136736

EN

This study describes the methodology for modelling a worm and worm wheel of a double enveloping worm gear with the use of a CAD system. An algorithm for generating a globoid helix is described. In addition, the methodology for modelling an hourglass worm thread with a straight axial tooth profile is presented. The shape of the hourglass worm tooth end with and without a trace modification is proposed. Moreover, a method for achieving a geometric modification of the tooth trace was developed. Next, the method for modelling the worm wheel teeth is described. A solid model of using a machining worm as a hob is applied. Owing to the limitations of a CAD system, which prevents the use of a direct machining simulation, an indirect modelling method is introduced. In the present study, different CAD techniques, both solid and surface, are applied. Knowledge of the correct modelling of the hourglass worm and worm wheel facilitates their generation and conducting various analyses, including a tooth contact analysis. CAD models are utilised to analyse the geometrical contact pattern in a CAD environment, to carry out FEM analysis, to manufacture real parts or to prototype models using the technique of rapid prototyping. They can be also used as master models for measurement, e.g. in optical technics.

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The methods of globoid surface modeling in CAD

Sobolak M., Jagiełowicz P. E.

Archives of Materials Science and Engineering

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2016

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Vol. 81, nr 2

76--84

EN

Purpose: Modeling of globoid worm surface is a difficult issue of modeling of complex surfaces in CAD. Worm gears are a challenge for designers because of the construction and the functions that have to be met, as well. There are very few specialized applications to generate this type of gears. The software intended to model of the worm gear wheel only is not accessible, so basing on general intending CAD systems is a necessity. Modeling of globoid worm surface can cause the problem. The examples of globoid helical surfaces modeling in CAD are accessible on the Internet, but often they 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 new solutions 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 carried out on the example of the warm lateral surface of the globoidal worm gears. In the first presented method the external program, that generates the script commands for AutoCAD system and lets generate the points of the globoid helix, was used. In the following two methods to model helixes, the possibilities of CATIA were used: creating the graph of two-dimension functions and comprising them into tree-dimension function and kinematic simulation, as well. In the globoid helix the pitch variation is included. Findings: The described methodologies are universal and allow to generate the globoid lateral-surface of worm on the basis of wormwheel constructional assumption and taken tooth profile. The advantages of CAD systems and their usefulness in the globoid worm 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 the limitation. Practical implications: The proper modeling of worm gear geometry in CAD allows to analyse the geometric cooperation, strength (by the finite element method), or to make a prototype for the preliminary tests with using of the rapid prototyping techniques. Originality/value: All three presented methods are innovative and allow to provide a correctly modeled globoid surface as a basis to create a complete model of the globoid worm.

3

Modelowanie powierzchni zębów ślimaka globoidalnego

Połowniak P., Sobolak M.

Stal, Metale & Nowe Technologie

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2015

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nr 1-2

62--65

PL

W artykule przedstawiono sposób modelowania powierzchni zębów ślimaka globoidalnego w systemie Catia V5R21. Powierzchnia jest modelowana z wykorzystaniem modułu Generative Shape Design. Wyznaczono ogólny matematyczny wzór na linię śrubową globoidalną i wykorzystano do modelowania powierzchni globoidalnego ślimaka. Wyodrębniono operacje, które zostały zautomatyzowane.

EN

This paper presents a method of modeling the surface of teeth of globoid worm using Catia V5 R21 system. The Generative Shape design modul is used for modelling. The general mathematical formula for the screw line of globoid was determined and used for modeling the globoid surface. Some operations have been automated.