## Introduction

GEAR is a computer program used to design toothed gears with the flank pitch line (GEAR_ZS program serves designing toothed gears with pitch helix). These can be classical gears of various degrees of complexity as well as power shift type gears. The program allows the user to achieve multi-criterion optimization of a gear due to combining different sets of criteria. At present, gear strength calculations can be done according to the ISO 6336 standard.

The application of multi-criteria optimization enables the user to have different approaches to designing gearboxes (any set of partial criteria and their weights is possible). The use of efficient optimizing procedures guarantees efficient search for the best solutions. The program - through the suitable structure of criterial functions - provides optimum load distribution for individual pairs of gears.

As there is a significant number of parameters, coefficients necessary to carry out calculations, a rule has been introduced that finally almost all the data will have initial values (suggested by the program). Obviously, almost each value will be able to be altered in an appropriate dialog window. All in all, even a user whose knowledge of toothed gear designing is limited will be able to do calculations and gain satisfactory results. Data concerning gear structure, element parameters, information on duty and optimization parameters will be shown in dialog window. It will be possible to modify all the above-mentioned data.

The figure below shows a power shift type gear.

The user has to determine the structure of the gearbox, what is performed in a very simple manner. The structure data for each transmission must be saved, just by using the dialog box, under the full control of the program (no accidental input errors) and then, the initial data for the gears will be generated from the templates. There is also possibility to present in appropriate window the scheme of an analyzed gearbox, during the entering input data of the transmission structure.

The software includes a module which allows setting initial parameters of toothed gears when a need to create new gearboxes arises. Particularly, the module adjusts the number of teeth to assumed number of gear ratios for all gears. Therefore, the initial gearbox design phase is significantly simpler. Adjustment of the number of teeth for a complex gearbox can be difficult because there is a great amount of available combinations. Thanks to this module, a user who wants to begin calculations of a gearbox only needs to define its structure and indicate gear ratios for individual gears.

Depending on applied modifications to particular gear parameters, an appropriate type of a gear is generated (three types of a toothed gear have been assumed). Appropriate dialog box serves for modifying the type of a gear in a very convenient way. The modification automatically adjusts parameters of the gear. The software validates correctness of applied parameters on the stage of data preparation - verifies the possibility of creating actual toothed gear - and suggests automatic modification of data. A user can allow automatic data modification, can modify the data manually, or ignore the warning. During optimization, the software on each of the processing steps also checks the possibility of creating an actual toothed gear. If data generated by an optimization procedure do not fulfill the requirements, then such a procedure will not launch. As a result, the calculations take less time.

Changes of input parameters are also controlled by the program - for example the program won't allow to enter the parameter value out of allowable range. A user, preferably an experienced user, can also modify the parameters within a specified range. A user with little experience in designing toothed gears can take advantage of pre-set parameters and conveniently launch and complete the calculations.

A module can be expressed in [mm] or [1/cal] (DP - Diametral-Pitch). It can also be selected in three different ways: as any module of the particular range, as any of the series of standardized modules types, or selected from among the series of types. A modification to a module for the given toothed gear results in automatic modification of all associated gears. During edition of a given toothed gear data, it is also possible to select the ‘same module for all gears’ option and then, all gears of a gearbox will be associated with a module that is expressed with the same units and they will be selected according to the pre-defined selection schedule.

Gear strength calculations are conducted according to the ISO 6336 standard. Parameters used in strength calculations, namely sigmaFlim – unlimited fatigue strength of a tooth root and sigmaHlim – unrestricted strength of a tooth side, were determined experimentally. The toothed gears used in the experiments were made of five types of steel and their toothing was finished in two ways (by grinding and shaving). Within the software, it is possible to enter parameters for a given material and conduct respective calculations. Modification of a material results in immediate modification of all parameters of materials used in the given toothed gear. Moreover, selecting appropriate option in the dialog box allows setting similar parameters of materials applied in all gears of a gearbox automatically.

The program uses efficient optimization procedures and, in case of gaining local minima, it resumes calculations automatically, modifying the start point adequately (three methods: two determined methods and one random sampling method). Such an approach enables one to search the solution space constantly. Optimization procedures can be automatically switched by the program or manually by the user.

Calculation results can be observed in a special dialog box. User can also enable or disable the additional window, which shows the variability of the optimization criteria as a function of the number of optimal steps. The graph shows plots for all selected sub-criteria and for global criterion. The X-axis scale is changing dynamically and it depends on the current number of optimal solutions. Data and results of calculations are saved to text files. Every such a text file with calculation results can be immediately used as a starting point for subsequent calculations.

The program can run under any 32-bit or 64-bit Windows operating system, but also it can be specially compiled and optimized for specific processors. It has an advanced multi-language installer, help documentation in various formats (HTML, CHM, and PDF) and multimedia demo. Program also updates automatically or on user demand.

The presented GEAR program has reached a certain stage already and its many features here discussed shall be gradually implemented, but even now most complicated and useful computations are fully possible. By using the GEAR program, it is possible to get a much shorter project cycle, optimized parameters of components and the optimized parameters of the whole gearbox.

This help contains information on how to use the program. Each stage of the project development is described in a separate chapter. Additional information can be found on the program website, from which you can also download various versions of the software.