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Leading Edge 2D CAD -Part II

......continued from Part I

Simple 2D is perfectly adequate for many kinds of technical drawings such as schematics, layouts and circuits. The current crop of 2D drawing tools from Autodesk, Microsoft and Intergraph are easy-to-use and smart. There's also enough difference between them to make one more suitable than another depending on your situation.

AutoCAD LT

Autodesk's tool of choice for 2D drawing is AutoCAD LT, junior sibling to the all-time CAD market leader, AutoCAD. For all intents and purposes AutoCAD LT is big AutoCAD without a programmable interface.

Symbols in AutoCAD are created as Blocks and Blocks cannot be collected into any kind of Block-Library in AutoCAD. For a long time, handling Block libraries in AutoCAD was cumbersome and tedious. Recent releases of AutoCAD LT, 2000 and 2000i, have an excellent facility for picking and placing symbol blocks. Working through Design Center, which is like a mini Windows Explorer within AutoCAD, you use the tree diagram on the left side to select a drawing that contains symbol blocks, and have the block names displayed in the right hand panel. If the blocks were created in LT 2000 with the option to create an icon, then they display as that icon, giving a visual thumbnail of the block. Then you can drag the desired symbol from the right hand pane into the drawing to insert it.

This makes AutoCAD LT 2000/2000i very convenient for diagram work. However, AutoCAD LT does not include any ready-made symbol libraries with the package. Libraries are not difficult to create, but ready-made libraries are far more convenient and efficient. Libraries are available from various sources, however most are to American standards, quite different from the IEC/ISO standard used in Europe, UK, Australia, New Zealand, and the rest of the world generally.

Autodesk also offers very good symbol libraries at quite modest cost, although you might have to do some detective work to find them for sale. Promotion is quite low-key for some reason. There are two packages, "Architectural", and "Engineering". The latter pack includes IEC and JIC electrical and electronic symbols, as well as HVAC and process plant symbology. The libraries are well organised and equipped with ready-made pictorial selection menus, and as library drawings for use with Design Center.

Using Autodesk Symbol Libraries with Design Center in AutoCAD LT.

AutoCAD LT has the advantage of using the DWG file format. This is the de facto CAD file format and probably the format that equipment fabrication and layout drawings will be supplied to you. AutoCAD LT does not however provide the smart symbol behaviour and automated interconnections of the other diagramming software products discussed here.

Intergraph SmartSketch

SmartSketch is a top class general 2D drafting and design tool that could also be used for office diagramming much more easily than conventional CAD programs. It comes from an engineering-based starting point rather than the office-based starting point of Visio and Actrix.

The core of SmartSketch is its 'smart' cursor and 'smart' object-snap methods. Instead of the diversions to set snap modes and the need to set up temporary guide-lines, the cursor continually shows fleeting geometrical relationships to nearby or distant objects and relevant snap possibilities as you drag a new line-end around seeking the correct end-point for it.

The SmartSketch screen display is not greatly different the others discussed here. However the strength of SmartSketch lies in its mode of operation.

You can group lines to make objects and make them retain geometric relationships to others, and to pivot or slide and behave in a proper mechanical manner. This makes it easy to animate mechanisms and check for clearances, although only in 2D.

In its current release SmartSketch includes drag-&-drop symbols with programmed behaviour rather like the core features of Visio and Actrix. It also has the automated interconnection system, where connection lines auto-adjust if you rearrange the associated symbols. SmartSketch really does merge full general CAD functionality with the 'smart symbol' drag-&-drop idea.

Showing more evidence of its engineering pedigree, SmartSketch can also work with AutoCAD DWG data. It works on DWG (AutoCAD native file format) and DGN (Microstation native file format) data files without translation. You can work on a drawing comprising data from AutoCAD and MicroStation as well as data created within itself. It also provides exceptional drawing aids for any type of drafting work. Its system of automatic object snaps and alignment with existing geometry features makes any sort of 2D drawing work very fast and accurate.

However, for electrical diagramming use outside America, SmartSketch is a disappointment. The symbol libraries provided are entirely American standards only. They provide 'metric' versions, but they are actually the same JIC symbols in metric dimensions. So far there appears to be no source of alternative IEC/ISO libraries. Intergraph advises that this is being addressed. Prospective users should contact their regional Intergraph office regarding localised symbol library availability.

Conclusion

Visio and Actrix can interchange data with AutoCAD DWG files, Actrix perhaps more completely. Symbol libraries provided with Visio are extensive and international. SmartSketch can also work the two most common CAD file formats and has an intelligent drawing interface, but is lacking in pre-drawn symbol content. AutoCAD LT 2000/2000i provides good DWG access and with AutoCAD Symbols plenty of international symbols sets. However, the drawing interface is not as intelligent as other packages and AutoCAD LT lacks built-in programmability.

These four products provide truly useful, powerful and easy-to-use new technology applied to 2D drafting the same! After using any of these drawing tools, it's a real 'drag' going back to old-fashioned CAD.

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