By now, everybody who designs mechanical products for a living has switched to 3D because 2D is dead, right? Hardly. For one thing, many users of 2D CAD software are perfectly comfortable, and capable, staying with 2D. Secondly, some classes of products just don’t need to be designed in 3D, so why switch? With the release of AutoCAD Mechanical, Autodesk gives new life to its premier 2D mechanical design and drafting package.
As in the past, AutoCAD Mechanical is a specialized application that sits on top of and integrates with the AutoCAD foundation. Just from the interface, you can tell that the two programs are obviously related, but different. AutoCAD Mechanical features toolbars and palettes specifically for mechanical design, such as standard parts libraries, mechanical line objects, and simple FEA (finite-element analysis) calculations for 2D objects. This additional functionality is powerful and adds to the learning curve already imposed by AutoCAD, but not too much more.
AutoCAD Mechanical 2004 also incorporates and includes in its price all of the functionality of what were formerly known as the Mechanical Productivity Extension and Power Pack (primarily standard parts and features). It’s worth the extra investment for an application that is optimized for a given task-2D mechanical design and drafting.
Probably the single most significant new feature in AutoCAD Mechanical 2004 is what Autodesk calls mechanical structure. This lets you organize geometry you create into components you can reuse. AutoCAD Mechanical displays components in a tree format in a graphical browser similar to those found in Mechanical Desktop, Autodesk Inventor, and other 3D modeling products.
Initially, the concept of mechanical structure is somewhat onerous, but once you get the hang of it, for most users it will prove to be a powerful and indispensable aspect of AutoCAD Mechanical. Mechanical structure lets you organize mechanical design and drawing data in a way that blocks, groups, and layers never could, but you can still use these features in conjunction with mechanical structure.
Before you can use mechanical structure, you must first ensure that it’s turned on. Open the Options (AutoCAD’s Options and Mechanical’s Options are now merged) dialog box from either the menu or command line, click the AM:Structure tab, and check the Enable Structure check box. Next, you’ll want to select a design mode, top-down or bottom-up, that best suits the way you work.
Although both methods yield the same end result, the routes you take to get there are exactly opposite. A top-down approach begins with a top-level component, usually a part or assembly, and ends with the elemental geometry as displayed in the browser. With a bottom-up approach, you begin with elemental geometry and end with the top-level component. Most users will probably prefer the top-down approach because you’ll be selecting and working with an entire component rather than its elemental geometry. AutoCAD Mechanical also lets you use a middle-out design process, which combines the top-down and botton-up approaches. Filters can hide views and features in the browser, but all geometry can be selected and edited at any time.
You can reorder components and organize them into different subassemblies and views, and the BOM (bill of materials) database ensures that each separate view isn’t counted in the BOM. If you copy a structured element, AutoCAD Mechanical creates the copy from the stored definition, and each component view instance can have independent view locations. The browser also tracks multiple instances of components, so a change to one reflects in all instances in an assembly.
The associativity of mechanical structure makes it much easier to annotate designs than in previous releases. Annotation views appear in the browser with a special icon and the designation (AV) at the end of the component name. If you don’t want to use mechanical structure, uncheck the Enable Structure check box to disable mechanical structure whenever it automatically is created-for example, when you insert standard parts and perform calculations and hides.
This release of AutoCAD Mechanical adds 16 new commands, most of them associated with mechanical structure. Those commands contain the prefix AMS as part of their name. Commands that are specific to AutoCAD Mechanical, but not directly associated with mechanical structure, have the prefix AM in their names. Of the new commands, one of the most important that is specifically associated with mechanical structure is AMSHide. It performs hidden-line calculations based on user-defined foreground and background objects. It automatically breaks, heals, and recreates lines for geometry that is partially or completely hidden in drawing views.
All of the icons in AutoCAD Mechanical are revamped. Though this may seem a relatively minor change, it makes the product a bit more intuitive and gives it a more updated, contemporary look. The documentation for AutoCAD Mechanical 2004 is more comprehensive and useful than in past releases. The updated User Guide takes into account how and where mechanical structure affects the concepts and exercises contained in the book. Most of the online Help topics that cover creating, editing, and annotating mechanical designs discuss the subject at three different levels-conceptual, procedural, and reference. This three-pronged approach is helpful for most users, especially for concepts such as mechanical structure that are difficult to convey. AutoCAD Mechanical online Help is separate from AutoCAD Help. This speeds searches when you look for information on issues specific to mechanical design. Annotation enhancements let you access BOM attribute values from the Amnote command dialog box. You can also add and delete leaders from notes without losing their associativity with the object they annotate.
Mechanical structure is the major feature that sets AutoCAD Mechanical apart from regular AutoCAD for mechanical design. Although you’re in a 2D design environment with AutoCAD Mechanical, the mechanical browser and the way components and views are arranged are subtle introductions to the way you play the game in 3D (Inventor) and may you transition to 3D over the long haul. To reiterate the question I posed up front: Who said 2D for mechanical design was dead? Not me. Autodesk, too, says it is committed to AutoCAD Mechanical development and support for several future releases and will ship it concurrently with future releases of AutoCAD.