Mechanical Design Handbook

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Showing posts from 2008

Dynamic Simulation Tutorial: Setting up 3D Contact in UG NX4 Motion

Which software are you using in your mechanical design project? Advertisement I have been using Solid Edge 3D CAD software for 1-2 years for my mechanical design projects in the past. But now, according to the standardization in my design organization, I have to switch to use Unigraphics software instead, or we call it in short as "UG NX4" (the latest versions are simply called NX ). To be honest, at first, I still liked Solid Edge because I think I can make modeling and assembly in Solid Edge faster and easier than in UG. But one of the good things for UG is the Motion Simulation module that helps me simulate the movement of mechanical assemblies before releasing for manufacturing. I know that Solid Edge also has this kind of simulation module, but I didn't have a chance to use it (no license). So in this post, I would like to share how easy it is to set up motion simulation in UG NX4. Let's start with a very simple modeling. ...

Solid Edge Motion Simulation with Excel VBA - Part 3

In a previous example , I showed how to control variables in a Solid Edge sketch using a direct link to an Excel spreadsheet. In this example, I am going to show how to use VBA (Visual Basic for Applications) in Excel to control the variables in a Solid Edge sketch directly via the API. Advertisement 1. Setup Excel VBA Create a new file in Microsoft Excel. Press Alt+F11 to enter the Microsoft Visual Basic window as shown below. Figure 1: The VBA Editor environment. Right-click in the Project Explorer on the new file name (in this example, Book2 ) > Insert > Module . 2. Add References To make Solid Edge type libraries available to the Visual Basic Object Browser, click References on the Tools menu (or Project menu depending on your version). On the References dialog box, select the Solid Edge libraries you want to access (specifically the Solid Edge Framework Type Library and Solid Edge Part Type Libr...

Solid Edge Sketch Motion Simulation using Excel VBA - Part 2

To link Solid Edge variables to Microsoft Excel, we can do so by entering a formula in the variables table or by using VBA code. Advertisement In this post, I would like to show how easy it is to make it using the variables table. You can use the Variable Table to define and edit functional relationships between the dimensions of a design in a familiar spreadsheet format. The Variable Table is accessed with the Variables command on the Tools menu (or the Tools tab > Variables group in modern versions). There are two types of variables: dimensions displayed in the design and variables you create directly in the Variable Table. Dimension variables directly control elements of a design. Variables that you create cannot directly control the design but can drive dimension variables. A user variable must be set equal to a value or mathematical expression; for example, PI = 3.14159. Let's begin... 1. Create the Mechanism Sketch ...

Solid Edge Sketch Motion Simulation using Excel VBA - Part 1

Solid Edge features a very useful application called " Motion " which allows users to simulate the movement of mechanical parts. This enables machine designers to test and ensure that the movement of their mechanism is exactly as expected before manufacturing parts. This helps save a lot of money. Advertisement However, instead of using the " Motion " application, I would like to show you how to simulate the motion of mechanical parts using a sketch in Solid Edge together with Microsoft Excel . Why? Most of the time, I start my mechanical design with the concept and layout using sketches. If we could simulate the motion of mechanical parts in a sketch, it would help me a lot. I got this idea when I was playing with sketches and constraints in Solid Edge . Solid Edge allows us to change the dimensions easily by just rotating the mouse wheel. Figure 1: The Concept — Using VBA to "push" dimension values from E...

Solving Nonlinear Engineering Equations with Excel Goal Seek

Problems in mechanical design often require the solution of nonlinear equations. A classic example is finding the roots of a polynomial stress function: 3x 3 - 20x 2 + 1000x + 12000 = 0 These are known as root solving problems : finding the value of x where f(x) = 0 . While you could solve this by trial and error (guessing values until the result is zero), or use the mathematical Newton-Raphson method , there is a faster way for the practicing engineer. Advertisement In this post, I will share a simple technique to solve these problems instantly on your desktop using Microsoft Excel Goal Seek . No VBA programming or expensive MATLAB license is required. Step-by-Step: Using Goal Seek for Engineering 1. Setup the Spreadsheet Open Excel and set up two cells: one for your input variable ( x ) and one for your equation ( f(x) ). The formula cell must mathematically reference the input cell. 2. Locate the Tool In modern...

Stress Analysis Explained: Mohr's Circle, Tresca, and Von Mises

The German engineer Otto Mohr (1835-1918) developed a useful pictorial interpretation of the equations for finding principal stresses and maximum shearing stress at a point in a stressed member. Advertisement This method, commonly called Mohr's Circle , involves constructing a circle where the coordinates of each point represent the normal and shearing stresses on a specific plane. The angular position of the radius gives the orientation of that plane. Understanding the Plot Figure 1: The geometric relationship between Normal Stress (σ) and Shear Stress (τ). Coordinate Rules: Normal Stresses (σ): Plotted on the horizontal axis. Tensile (+) is right; Compressive (-) is left. Shearing Stresses (τ): Plotted on the vertical axis. Clockwise rotation is above the axis; Counter-clockwise is below. The results obtained from Mohr's circle are identical to the equations derived from the free-body diagram. ...

DIY Motion Simulation: Visualize Machine Timing with Excel VBA

Motion Simulation with Microsoft Excel Mechanical design usually deals with the movement of several parts. There are a lot of software packages that help simulate the movement of machine parts, such as NX (UG), Solid Edge, and SolidWorks. Advertisement But how do you make a simulation without those expensive software packages? I use Microsoft Excel to simulate my timing diagrams. As you can see in the video above, it provides a clear visual representation of the machine's cycle. How it Works Actually, it is nothing but motion simulation using the graphing method in Microsoft Excel. While it cannot simulate complex 3D collisions or physics like high-end CAD, it helps you get a feel for how your machine will behave according to your timing diagram. This technique uses VBA (Visual Basic for Applications) to control the movements. Here is the general workflow: Prepare the Spreadsheet: Create a table defining the geometry (...

Timing Belts Explained: Mechanics, Profiles (HTD vs. Trapezoidal)

Timing belts solve the slippage problems inherent in flat, O-ring, and V-belts by utilizing a flexible tooth molded to a belt with internal tension members. These teeth are flexible, allowing the load to be distributed across all teeth in contact with the pulley, ensuring precise power transmission. Advertisement Timing belts belong to a larger category of power transmission devices known as synchronous drives . Unlike friction-based drives, these belt or cable-based systems have the distinct advantage of zero slip . This "positive drive" capability means these belts perform reliably even in wet or oily conditions, provided the pulleys are made of corrosion-resistant materials like stainless steel or plastic. Figure 1: Timing belts maintain an exact speed ratio, crucial for engines and automation. Tooth Profiles: The Evolution of Design Timing belts are categorized by their tooth profile and manufacturing method....