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Applications: Autodesk AutoCAD 2004/2005, Autodesk Mechanical Desktop 2004/2005
Mechanical Desktop (MDT) is a three-dimensional, parametric solid modeling program that runs on top of AutoCAD. Being parametric and feature based, you can easily modify solids and apply constraints to them. Applying constraints simply means locking together assembly model subordinate parts through commands that restrict (or constrain) their independent movement. Constraints provide a simple method of creating and updating assemblies. But before parametric modeling programs flooded the market, AutoCAD offered basic solid modeling and the modeling capability of AutoCAD can be very useful as a conceptual design tool even without the parametric, feature based capability. Because MDT runs on AutoCAD, you can build these basic solids within the program and convert them to solids for constraining. In fact, you can use the basic solids intelligently in MDT even without converting them. These solids are called core solids or 3-D solids. In this article, we explain how to use core solids in MDT.
From AutoCAD to MDT in 3-D
This month we'll discuss some methods for creating core solids. Then, we'll explain how core solids can function as parts in MDT assemblies. We'll discuss when you can and can't apply constraints to these core solids. Finally, we'll explain how to convert certain solids so that you can constrain them and work them into MDT assemblies.
Creating basic models
The two simplest methods of creating a solid are the EXTRUDE and REVOLVE commands. For each command, you need a 2-D closed polyline as a sketch (2-D layout or drawing) to begin the operation. For our examples, we used a simple rectangle, shown in Figure A in Perspective view.
Using the EXTRUDE command
The EXTRUDE command is probably the most common way to create a 3-D model from a 2-D sketch. To extrude the rectangle into a box, as shown in Figure B on the next page, we used the RECTANGLE command by entering rec at the command prompt. In MDT, choose Design I Solids I Extrude from the main menu. You can also enter extrude or ext at the command prompt.
Note: Although you can access solid modeling commands through menus or the command line, the MDT toolbar for MDT-specific commands works well and it's easy to use....