![]() If the moment of inertia unit is different from Kg.m 2, you’ll need to follow steps 2, 5, and 6. In the example above, the value we are looking for is I2 5,556 Kg.m 2, as the assembly will rotate around the Y-axis. The image below is an example of how it should be sent. Example 6: When r 1 is 10 m, r 2 is 20 m, and the mass of the annular ring is 14 kg, calculate the moment of inertia of the ring. We have for hollow cylinder, MOI (I) MR 2. Press the “Print Screen” key on your computer and send the image of the part + moment of inertia to Posibras. Example 5: If the mass is 10 kg and the radius is 7 m, determine the hollow cylinder’s moment of inertia. The moment of inertia values related to the objects that will rotate around the Y-axis are shown in the I2 box. A new assembly properties screen will appear.Ħ – In this new properties screen, click on the “Physical” tab, then the “Update” button, followed by the “Principal” button. This way, the rotation axis of the disc will be the Y-axis.Ĥ – Also align the Inventor’s Origin with the center of the assembly’s rotating disc using the “Constrain” icon.ĥ – Right-click on the first item in the left menu and then left-click on the “iProperties” submenu. ![]() In the document properties screen, click on “Units” and change the Length unit to meter and Mass to Kilogram.ģ – Align the rotating disc of the assembly with the XZ plane using the “Constrain” icon. All items should be correctly defined in terms of dimensions and mass/material.Ģ – Change the distance measurement units to meters and the mass units to kilograms using the Tools / Document Settings menu. Generally, for uniform objects, the moment of inertia is calculated by taking the square of its distance from the axis of rotation (r2) and the product of its. Inventor 1 – Create an assembly with only the items that will be moved by the indexing table (disc, devices, screws, parts, etc). In the example below, the assembly will rotate around the Y-axis, so the moment of inertia is shown by Solidworks under item lyy. Check which UCS letter represents the axis your assembly will rotate around. Therefore by finding the moment of inertia about the x and y-axis and adding them together. When the moment of inertia calculation screen appears, click on the Options button and change the mass units to “Kilograms” and length to “Meters”.Ħ – Position the assembly so that you can read the moment of inertia data and see the colored UCS in the bottom left of the screen in the same view. Thus by using the perpendicular axis theorem, the equation for the polar moment of inertia about the z-axis (J ) is given by, Jo z x + y. The positioning should be “concentric”.ĥ – With no object selected, click on the “Evaluate” menu, then “Mass Properties”. You need to break the sphere into infinitely thin parts and add. What makes it harder is for the mass you used spherical coordinates (as the density only depends on the radius) where as the moment of inertia needs to be calculated in cylindrical coordinates. The positioning should be “coincident”.Ĥ – Also align the Solidworks Origin with the center of the assembly’s rotating disc using the Assembly icon (clips). To calculate the moment of inertia your working will be similar to the mass. All items should have correct dimensions and masses/materials defined.Ģ – Let the assembly float by right-clicking on the assembly (a).ģ – Align the rotating disc of the assembly to one of the standard planes using the Assembly icon (clips). Solidworks 1 – Create an assembly with all the items that will be moved by the indexing table (disc, devices, screws, parts, etc). Please consult your CAD manufacturer for the exact procedure. Other CADs have similar methods for this calculation. We’ve created the step-by-step guide below to help identify the moment of inertia of your assembly that will be moved by the indexing table, using the CAD tools Solidworks and Inventor. Calculating the moment of inertia of a rod about its center of mass is a good example of the need for calculus to deal with the properties of continuous mass distributions. There are several ways to determine the moment of inertia:Ī) manually, using mathematical calculationsĬ) with CAD software (Solidworks, Inventor, Catia, NX, etc…) The further the mass is from the center of rotation, the greater the moment of inertia.Ĭalculating the moment of inertia for your assembly is crucial for determining the best indexing table for your needs, without risking oversizing and incurring excessive costs, or undersizing and not meeting the required resistance. The unit is typically Kg.m 2 (kilogram times square meter). )\).Moment of Inertia Calculation in Solidworks or Inventor In mechanics, the moment of inertia, or mass moment of inertia, expresses the difficulty in changing the motion state of a rotating body.
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