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KISSsoft Tutorial: Sizing of helical gears __________________________________________________________________________________________ For Release 04/2006

Last modification 05.05.2006 16:45 __________________________________________________________________________________________

Example problem, starting KISSsoft

Example problem A helical gear pair is to be designed such that it has a lifetime of 5'000h when transmitting 5kW at 400Rpm (Application factor = 1.25). The ratio shall be 1:4 (reducing speed), the gear material is 18CrNiMo7-6. The gear pair is to be optimized in terms of noise / contact ratio. The lifetime calculation is to be performed according to ISO 6336, method B.

Starting gear pair calculation After installation and release of KISSsoft as test or commercial version, KISSsoft is started using „Start/Programs/KISSsoft-Hirnware 04-2006/KISSsoft-Hirnware“, (see also the tutorial No. 001).

Figure 0-1 Starting KISSsoft, starting of gear pair analysis module

The example used in this tutorial can be opened using “File / Open” and selecting „Tutorial-009-Step1“ (to “Tutorial-009-Step5”), see figure below. In each of the different sections of this tutorial, it will be indicated which step should be opened.

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Figure 0-2 Opening the example problem files at different stages of progress.

Rough sizing of gear pair

Entering the basic data After having started the helical gear pair analysis module, in the top right corner of the window shown below, the power rating can be defined. Furthermore, the analysis method and the gear materials should be selected from the drop down menu (press small vertical arrow).

To get directly to this level, open file „Tutorial-009-Step1.Z12“ Note that gear 1 is used as reference gear

Figure 0-1 Defining power rating, required lifetime, analysis method and material.

Executing rough sizing function KISSsoft offers a function where a sensible gear pair is proposed based on the power rating and lifetime required alone. For this, use the „rough“ button in the upper right corner of the window, and a window „Spur / Helical Gear sizing“ will show where the sizing parameters can be defined. Of particular importance is the required ratio including the definition of a permissible ratio error. Other parameters such as helix angle or centre distance may also be pre-defined.

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The data displayed in the columns can be changed using right mouseklick.

Figure 0-1 Helical gear pair rough sizing

Using the button “Sizing”, KISSsoft will calculate different possible gear pairs meeting the requirements. These solutions are shown in a list. To select a solution (hier with centre distance of 104mm), click on it and press “Choose variant”. The data will be visible in the main window:

To get directly to this level, open the file „Tutorial-009-Step2.Z12“

Figure 0-2 Module, number of teeth, width and addendum modification as proposed by KISSsoft.

Modifications The theoretical values calculated, e.g. for the width b of the gears, can now be modified manually. Change the width of gear 1 to 28mm, gear 2 to 27mm (type values into respective fields). To modify the addendum modification, press “N” (button to the right of the field for the number of teeth) and the following window will show, giving information about the reference profile and addendum modification:

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List with reference profiles Current reference profile

Figure 0-1 „N“ mask, information on reference profile

To the right of the addendum modification coefficient, a sizing button is available. Using this button, KISSsoft will propose a sensible addendum modification according to different criteria. In this example, the addendum modification should result in balanced specific sliding. For this, press the sizing button, see marking in Figure 0-1, and the window as seen in Figure 0-2 is shown. By pressing “A”, the respective addendum modification will be used and the window will close. Then, the window as shown in Figure 0-1 can be closed using „Ok“.

Different methods for defining a sensible addendum modification are available Resulting / proposed addendum modification Maximum and minimum values (pointed tooth / undercut)

Figure 0-2 Sizing of addendum modification

The addendum modification coefficient is now available in the main window. Press „Calculate F5“ (see left marking in Figure 0-3). The safety factors for tooth root and flank, the safety against scuffing (flash and integral temperature criterion) and the contact ratio are calculated when the button „Calculate F5“ is pressed (see lower marking in Figure 0-3). The main mask should now look as follows(there may be small differences in e.g. the addendum modification factors):

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To get directly to this level, open file „stirnrad-feinauslegung-step3.Z12“ and press „Calculate F5“

Figure 0-3 Execution of calculation, results

Fine sizing of gear pair

Starting the fine sizing function Now that a gear pair meeting the requirements has been defined using the rough sizing function, this gear pair should be optimised. The objective is to get a gear pair with an optimal contact ratio. For this, press the sizing button „fine“ (to the left of the button „rough“ for the rough sizing function) and a window “Spur gear fine layout” will appear. In this window, parameter ranges and step sizes can be defined. KISSsoft will then search for a suitable gear pair solution within these parameter ranges:

- Range for module - Range for helix angle - Range for centre distance (to activate, set flag „Variable centre distance“)

In addition to this, the following can be defined - Upper limit for the tip diameter - Lower limit for the root diameter - Number of teeth (if 0 is used, the number of teeth will be defined by KISSsoft

automatically) For this example, the settings should be chosen as shown in Figure 0-1. The sizing is executed by pressing „Dimensioning“. Using the function „Judgement“ (which will be activated once the sizing function has been executed) a list is shown, where all solutions are compiled (see Figure 0-2). In this example, the objective is to get a gear pair with low noise. Hence, the variant getting the best rating in terms of noise is chosen. For this, see the report as shown in Figure 0-2), where

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the variants are rated according to different criteria. One of them is noise, and the solution with the best rating in terms of noise is No. 63 (see marking). Using the button „Chose variant“ (see right marking in Figure 0-1), the dialog as shown in Figure 0-3 appears, where the variant to be selected can be defined (in this example, No. 63).

Define required ratio and permissible error Using the sizing buttons, KISSsoft will propose sensible ranges Set to 300 Chose whether the centre distance remains fixed or not

Figure 0-1 Fine sizing window, definition of parameters

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Figure 0-2 List of solutions found, rating of solutions

Figure 0-3 Selection of variant, here No. 63

Once the above dialog has been closed using „Ok“ the optimised tooth data as defined by KISSsoft fine sizing function will be available in the main window. The lifetime calculation can then be executed using „Calculate F5“. Note: the procedure has been described here only briefly. In reality, a carefull investigation of the solutions as listed under “Geomety” should be done. It may well be that another solution is to be preferred due to other considerations. Use the “Graphic” button to compare the solutions graphically:

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Figure 0-1 Graphical comparison of solutions

Results of the fine sizing function The contact ratio is now slightly above 3.1 (see Figure 0-3), which means that the variation of the contact stiffness is small during the meshing and vibrations will be minimal.

To get directly to this level, open file „Tutorial-009-Step4 .Z12“

Figure 0-1 Results and data as defined by the fine sizing function

The resulting 2D tooth form can be shown using the 2D graphics button (close with „Ok“).

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Figure 0-2 Resulting tooth form (base circle and line of action are shown in red)

The contact stiffness can be shown using “Calculation / Contact stiffness”:

Figure 0-3 Course of contact stiffness.

Dimensioning of a deep tooth form In a third step, the resulting contact ratio should now be increased by using a deep tooth form. Again, an optimised tooth form should be proposed by KISSsoft. For this, the fine sizing function is used again. In the fine sizing window, select „Settings“ and set the flag „Sizing of Deep tooth form (Z19h)“. Close the settings window using “Close” and execute the fine sizing again using “Dimensioning”.

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Figure 0-1 Settings for fine sizing function, select „Sizing of Deep tooth from (Z19h)“

By pressing „Jugment“, the report with the ratings can be viewed again. The best solution in terms of noise now is solution No. 30. Chose this solution by pressing „Chose variant“ and the respective gear data is made available in the main window of the gear pair analysis module. Since the reference profile has changed (due to the deep tooth form), the following message is shown:

Figure 0-2 Message that the reference profile has been changed.

The new gear data is now available (changes in number of teeth, helix angle, addendum modification), the calculation of the contact ratio is executed using „Calculate F5“:

To get directly to this level, open file „Tutorial-009-Step5 .Z12“

Figure 0-3 New gear data, results, resulting contact ratio.

After having executed the calculation, the gears can be viewed using the 2D graphics button (right marking in Figure 0-3), close this window with “Ok”:

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Figure 0-4 Resulting tooth form. Note the changes compared to Figure 0-2

The new reference profile can be shown using the „N“ button (upper marking inFigure 0-3):

Figure 0-5 New reference profile.

The contact ratio is now very close to 3 (see results in Figure 0-3), resulting in a very even contact stiffness:

Figure 0-6 Contact stiffness course. See Figure 0-3 on how to get this window.

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Additional settings for strength analysis For the final strength analysis, information on the lubrication and face load coefficient is required. Use the two buttons “Inputs pair“ and „Lubrication“ in the main window:

Figure 0-1 Open window for face load coefficient and lubrication

Chose type of lubrication, lubricant, temperatures. If „own input“ is used for lubricant, a lubricant can be defined using the „Plus“ button. The list of lubricants can also be modified using the lubricants database.

Figure 0-2 Lubrication parameters.

The face load coefficient can be define according to methods A, B or C (see DIN 3990 or ISO 6336) For instructions on the face load coefficient, see „anl-004-xyz.doc“ which is available from the KISSsoft customer support.

Figure 0-3 Define further parameters, especially face load coefficient.