Mechanical Design Handbook

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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....

Fastener Design Guide: Joint Selection, Shear, and Preload

Selecting the right fastener is not just about size; it is about understanding the complex mechanics of the joint itself. A properly designed bolted joint acts like a rigid spring system, where the balance between bolt tension and joint compression determines safety and longevity. Advertisement JOINT DESIGN AND FASTENER SELECTION Figure 1: High-strength socket head cap screws are critical for precision joint design. Joint Length The longer the joint length (grip length), the greater the total elongation required to produce the desired clamp load. In design, a longer joint length generally decreases the potential loss of preload over time due to settling or vibration. Joint Material Stiffness If the clamped material is stiff relative to the bolt, it will compress less under load. This results in a "less sensitive" joint—one that is more resistant to preload loss from brinelling (surface indenting), relaxation, or loosening. ...

The Engineering Design Process: Synthesis, Analysis, and Creativity

Success in the competitive landscape of modern manufacturing depends on a rigorous and structured approach. All design activities must be anchored by these five core pillars to ensure a product is both functional and viable: Identify Customer Needs: Deeply research the "voice of the customer" to understand the true requirements. Problem Definition: Distill those needs into essential technical problems, boundary conditions, and constraints. Synthesis: Conceptualize the solution by mapping functional requirements to specific design parameters. Analysis: Model the proposed solution to establish optimum conditions and final parameter settings. Validation: Rigorously check the resulting design against the original customer needs to ensure total alignment. Advertisement The Iterative Nature of Design Engineering design is rarely a straight line. It proceeds from abstract, qualitative ideas to precise, quantit...

Cam Design Essentials: Kinematics, Pressure Angles, and CNC

Mechanical cams remain the "heart of automation," providing precise timing and motion control in high-speed machinery. Understanding the geometry and dynamics of these systems is essential for modern machine design. Advertisement Classes of Cams Cams may, in general, be divided into two classes: uniform motion cams and accelerated motion cams. The uniform motion cam moves the follower at the same rate of speed from the beginning to the end of the stroke. However, as the movement starts from zero to full speed instantly and stops in the same abrupt way, there is a distinct shock at the beginning and end of the stroke if the movement is at all rapid. In machinery working at a high rate of speed, therefore, it is important that cams are so constructed that sudden shocks are avoided when starting the motion or when reversing the direction of motion of the follower. The uniformly accelerated motion cam is suitable for moderate speeds, but it ha...

Flywheel Construction and Design: A Guide to Energy Storage Wheels

A flywheel is a mechanical device with a significant moment of inertia used as a kinetic energy storage reservoir. Flywheels are designed to resist changes in rotational speed, helping to steady a shaft's rotation when a fluctuating torque is applied (as seen in reciprocating engines) or when the load itself is intermittent (such as in piston pumps or punching presses). Advertisement Beyond smoothing rotation, flywheels are increasingly used to produce high-power pulses for industrial experiments. In these cases, drawing the required instantaneous power from an electrical network would create unacceptable spikes. Instead, a small motor slowly accelerates the flywheel between pulses, storing energy to be released in a single high-torque event. Figure 1: Modern flywheels are sophisticated energy storage systems for steadying rotation and delivering power pulses. 1. Classification: Balance Wheels vs. Flywheel Pulleys Flywheels are gene...