KISSsoft Tutorial 012: Sizing of a fine pitch Planetary Gear set. 1 Task. 2 Starting KISSsoft

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KISSsoft Tutorial: Sizing of a fine pitch Planetary Gear set KISSsoft Tutorial 012: Sizing of a fine pitch Planetary Gear set For Release: 10/2008 kisssoft-tut-012-e-sizing-of-planetary-gear-set.

1 KISSsoft Tutorial: Sizing of a fine pitch Planetary Gear set KISSsoft Tutorial 012: Sizing of a fine pitch Planetary Gear set For Release: 10/2008 kisssoft-tut-012-e-sizing-of-planetary-gear-set.doc Last modification: 03/11/ :28:00 1 Task A planetary gear set has to be designed with input torque 450 Nmm (0.45 Nm) at rpm. Nominal transmission ratio is The required lifetime is hours, with an application factor of K A =1.25. The package size (outer diameter of the gear rim) is 35 mm, including 3 mm of material between root circle and outer diameter. The gears are sintered from powder metal. The module must be larger than 0.5 mm (due to the needs of manufacturing). The tooth form shall be optimised to take full benefit from the fact that the gears are net shaped. As calculation method, the method according to AGMA 2001 is used. 2.1 Starting the software 2 Starting KISSsoft Upon installation and activation of the license KISSsoft is started via Start -> Programs -> KISSsoft /KISSsoft. The main window opens (see Figure 2.1-1): Figure 2.1-1: KISSsoft main window. 1 / 14

2.2 Starting the Calculation Module Planetary gear Start the Planetary Gear pair calculation module by double-clicking the appropriate entry within the Modules window in the upper left

3 Standard Settings When using the AGMA 2001 method for a planetary gear set, it makes sense to activate the graphical method for the factor Y (affects root stress calculation).

2 2.2 Starting the Calculation Module Planetary gear Start the Planetary Gear pair calculation module by double-clicking the appropriate entry within the Modules window in the upper left corner of the main window calculation module See Figure Figure 2.2-1: Select Calculation Module Planetary Gear from s window Modules. 2.3 Standard Settings When using the AGMA 2001 method for a planetary gear set, it makes sense to activate the graphical method for the factor Y (affects root stress calculation). Go to the tab Strength and press details in the area: Pair data. Activate the graphical method and define where the force shall be applied. Since in the first design phase some of the solutions found will have geometrical errors (which by default will cause KISSsoft to abort the calculation) it is recommended to go to the module specific settings and activate Allow large addendum modification and Don t abort when geometry errors occur. This will cause KISSsoft to continue with a calculation even if an error occurred. See Figure Figure 2.3-1: Define details of strength and Module specific settings for this example. 2 / 14

2.4 Setting the boundary conditions Go on the area Geometry and set the desired number of planets (Figure

Figure 2.4-1: Define the number of planets. Figure 2.4-2: Define load distribution coefficient. 2.5 Rough Sizing Return to the main dialog with [Ok].

Enter the application factor (3) and the lifetime (4).

3 2.4 Setting the boundary conditions Go on the area Geometry and set the desired number of planets (Figure 2.4-1). The load distribution factor K increases the load applied to one planet. It is set to 1.0 here. Figure 2.4-1: Define the number of planets. Figure 2.4-2: Define load distribution coefficient. 2.5 Rough Sizing Return to the main dialog with [Ok]. Open rough sizing and set desired calculation method (1) and material (2). Enter the application factor (3) and the lifetime (4). Click on the radio-button beside the power field to define the load (5), see Figure Figure 2.5-1: Calling the rough sizing function. 3 / 14

respective field (5-3). 5-3: Setting the unit of the torque.

4 Figure 2.5-2: Setting materials, calculation method, application factor and required lifetime Setting the load Set the unit for the torque by right clicking on the respective field (Figure 2.5-3). Figure 2.5-3: Setting the unit of the torque. Define the reference gear (1), the calculated value (2) (as torque and speed are defined, the power is calculated), and enter the data for speed and torque (3) (see Figure 2.5-4). Figure 2.5-4: Setting the load. 4 / 14

Therefore, set the range for the number of teeth down to 9 to 12 (7) to force KISSsoft to choose a larger module.

5 Enter the nominal transmission ratio (6). Figure 2.5-5: Rough sizing settings. If KISSsoft would calculate a proposal with the standard settings it would come up with a very small module. Therefore, set the range for the number of teeth down to 9 to 12 (7) to force KISSsoft to choose a larger module. In most cases it is not necessary to change the standard values for the tooth number. Close the input window with OK. Figure 2.5-6: Rough sizing conditions Limit geometry Press on [Calculate] (8). Have a look at the results. 5 / 14

6 Figure 2.5-7: Rough sizing calculate If satisfied, return to the dialog by closing the editor and click on [Accept] (9), see Figure Figure 2.5-8: Rough sizing result. 6 / 14

In the Tolerances dialog select for each gear instance DIN 58405 10e, Figure 2.5-9. The 10 corresponds to the quality (width of the interval), where 10 is low quality.

7 The main dialog is now filled with the data of the solution generated by the rough sizing function. Since the module is smaller than one, it is recommended to switch to another standard for the tolerances. Go on the tab Tolerances. In the Tolerances dialog select for each gear instance DIN e, Figure The 10 corresponds to the quality (width of the interval), where 10 is low quality. The character e is the definition of the upper bound of the interval and therefore defines the backlash. Figure 2.5-9: Setting the tolerance. After the definition of the tolerances, you may want to give the face width a nicer value (in this example we leave the values as they are (1), see Figure Click on [Calculate F5] (2). You get first results of the rough sized planetary gear set in the Result-overview (2a) (Figure 2.6-1). 2.6 Fine Sizing With this the presizing step is finished. The purpose is to give the fine sizing function values of roughly the right size for the next steps. Now to get an optimized solution, click on the button for the fine sizing (3), Figure / 14

Figure 2.6-1: Calculate, check the results and call the fine sizing function. Check the value for the nominal ratio first (might have changed sligthly because of the rough sizing step) (1).

8 Figure 2.6-1: Calculate, check the results and call the fine sizing function. Check the value for the nominal ratio first (might have changed sligthly because of the rough sizing step) (1). Define the target value for the reference circle of the rim (2). Enter the desired range and step size for the module (KISSsoft will choose very small values automatically). Enter the target pitch diameter. To find the right diameter, subtract from the outer diameter of the gearbox (35mm) twice the 3mm of material below the root circle (gives 29mm) and then reduce it by another 2*1 mm for the dedendum (this value must not be accurate, because the permissible deviation is set to 10%). Click on sizing button for centre distance (4) which will give you the possible range for that value. To force the root circle of the gear rim to leave enough material below the root, enter an arbitrary value into the respective field (here: 35-2*3mm = 29mm) (5). See Figure Figure 2.6-2: Settings for the fine sizing. Since the graphical method is used for the root stress, the calculation of the tooth form for every solution found has to be activated. For this, click on [Conditions II] (6). Activate the calculation of the contact stiffness. This will also cause KISSsoft to calculate the tooth form. 8 / 14

Looking at the safety factors only, solution 15 looks promising: the safety factor for the root is large enough, the flank safety by far sufficient.

9 Figure 2.6-3: Calculate contact stiffness. Click on [calculate] and the fine sizing is starting. When solutions are found (otherwise a message will tell you that no solutions could be found) click on tab Graphics. Looking at the safety factors only, solution 15 looks promising: the safety factor for the root is large enough, the flank safety by far sufficient. The root safety usually can be improved be changing the root geometry, so the flanks safety is more important. Usually you would check the other criteria (as profile overlap, specific sliding, ) as well. Since this is strongly depending on the problem treated, we will skip that part in this tutorial and accept solution number 15. Refer to the tutorials in the list at the end of this paper to learn more about the fine sizing function. Figure 2.6-4: Graphical presentation of the results 9 / 14

6-6), the result overview gives a very brief overview, the full set of information about the selected solution is

10 Go to the fine sizing tab Results and choose variant by double clicking on variant 15 or take the button [accept] (Figure 2.6-5). Figure 2.6-5: Select solution. Back in the main dialog (Figure 2.6-6), the result overview gives a very brief overview, the full set of information about the selected solution is presented in the report. Click on F6 to obtain the report. At this point the sizing of the planetary gear set is completed. Figure 2.6-6: Calculation Results overview. 10 / 14

This section will cover the most common modifications of the tooth form of sintered gears. For more details about this topic refer to the tutorials in the list at the end of this paper.

11 2.7 Optimizing tooth form If the design of the gears is satisfied, the next step is to optimize the tooth form. Due to the fact that the gears are net shaped (in this case sintered) modifications can be done without additional costs. This section will cover the most common modifications of the tooth form of sintered gears. For more details about this topic refer to the tutorials in the list at the end of this paper. To enter the tooth form modification click on the menu Calculation ->Modifications, Figure Figure 2.7-1: Activate Tab Modification Figure 2.7-2: Defining details of profile correction. In the active tab Modifications a tooth form modification is possible. Click on the Sizing button and the window Sizing modifications is displayed (Figure 2.7-2). The option short profile correction, curved for tip relief is chosen to minimize the contact shock. This should be done on the Gear 2. Select Short profile correction curved and click on the button Calculate. KISSsoft calculates a proposal for the tip relief, starting (by default) half way down to the point of single tooth contact, with a value based on the calculated bending of the teeth. 11 / 14

For improvement of the initial tooth contact and due to the restriction of manufacturing by sintering it is necessary to define a tip rounding.

Figure 2.7-3: tip modifications Rounding of the tooth form.

12 For improvement of the initial tooth contact and due to the restriction of manufacturing by sintering it is necessary to define a tip rounding. Select Rounding from the dropdown list for Type of tip modification and enter an arbitrary value (here: 0.08 mm, already quite large) into the entry field for all gears 1 3 (see Figure 2.7-3). Figure 2.7-3: tip modifications Rounding of the tooth form. For the root, the best solution in most cases is an ellipse with a large radius at the end of the involute and a smaller radius in the middle of the root area between two teeth. For this activate the Tab Tooth form and adds the option Elliptic root modification and click on the sizing button to get a proposal for the elliptical form. Figure 2.7-4: Elliptic root modification adds the option. After these definitions have been done for all gears, click on Icon or F5. 12 / 14

13 In the next dialog activate the collision check. Figure 2.7-5: Calculation and presentation of the tooth form. Figure 2.7-6: Activating collision check and present Pair / 14

14 Click on the button (2) and select Join flanks (right). You should see small black boxes where the two flanks are in contact. A black box means contact or nearly contact, red boxes mean interference. Figure 2.7-7: Automatic join of the flanks, zooming and collision check. Use the + / - button to zoom in/out, click on the right mouse to open the menu, and finally use the buttons Figure to animate the graphic. Check if any of the modifications cause any problems, When satisfied, return to the main dialog. Press [Calculate F5] and check using the safety factors for the root whether the modifications improved the root strength or not. 2.8 Ongoing tutorials In these tutorials you can find further details about specific topics mentioned in this paper: - Tutorial 009, Sizing of helical gears - Tutorial 011, Tooth-Form Optimisation and Tooth-Form Modifications Specifically for Plastic, Sintered, Wire-Eroded and form-forged Gears 14 / 14

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