By Joe Greco
As more users make the move to 3D CAD programs, the need to convert data from one program to another is becoming ever more critical. This data may be a 2D CAD legacy drawing that a user would like to have as a feature-based solid model or a 3D model created in one CAD system format that is now needed in another.
When dealing with a 2D file, traditionally the only choice has been to build the 3D model manually. When working with a 3D file, a solid model from the exporting system can usually be read in, but it frequently needs repairs. And, more problematic, intelligent features such as holes and fillets that make the solid model such a robust tool are lost in the translation. Now, however, thanks to a new wave of intelligent CAD-conversion software, the days of remodeling and repairing may soon be over.
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The challenge in converting 2D mechanical CAD drawings to feature-based 3D solid models goes beyond the obvious problem of being able to read in 2D files and understanding how the different views form a 3D model. The software also has to know how to handle the extraneous 2D-only data such as text, hatchings, and dimensions as well as erroneous artifacts such as duplicate and overlapping lines. Here is the current lineup of products that can create 3D solid models from DXF or DWG 2D drawings, and a look at how they deal with the inherent technical obstacles.
AutoZ 3.0: Introduced in 1998, this $495 program was one of the first 2D-to-3D converters. Realizing the size of the AutoCAD market, developer EMT Software designed the program to work exclusively with Autodesk's Mechanical Desktop. When you select a 2D file to convert, AutoZ creates the 3D solid in the same file as the 2D drawing, complete with Mechanical Desktop features. In testing the program, I found that AutoZ did require some manual work to create the desired model. For instance, in one file I tested, a cutout that was hidden behind another in the side view didn't get added to the model and had to be created using the program's Slice tool. In the same test, counterbores shown in the drawing were not recognized as one feature, but as two separate holes, and the profiles that were created had no dimensions. However, any extraneous data in the 2D files did not create problems for AutoZ.
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| AutoZ creates a 3D solid model in the same file as the 2D drawing, complete with Mechanical Desktop features. |
2Dto3DCAD.com: This new service, which runs on a portal called ASPire3D.com, was created by application service provider Imagecom, the company that developed FlexiDesign, a 2D-to-3D conversion program that is now the engine behind 2Dto3DCAD.com.
After registering and logging on to this service, you arrive at a page where you must choose between Self-Serve and Full-Serve options. You would choose Self Serve if you had already eliminated all the 2D-only data in your file. Or you would pick Full Serve if you wanted technicians at 2Dto3DCAD.com to perform this task for you. Self Serve takes you to an eight-step questionnaire that helps you determine whether the removal of the 2D entities is complete and asks for additional information about your 2D file, including the number of views and their positions. To use the Full Service option, you simply choose the DXF or DWG file you wish to send and then select whether you want to receive Mechanical Desktop or Autodesk's Inventor 3D files in return. Other options will return featureless solids in either the AutoCAD 2000 format or the IGES or STEP neutral file formats. Another nice feature of 2Dto3DCAD.com is that it has a software mechanism that automatically cleans up drafting errors, deleting tiny stray geometry and connecting joining lines and arcs that may have become broken.
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| Converting this 2D file using AutoZ required manually adding several design elements and dimensions. |
When I used the service to convert a 2D file, I received a 3D model complete with dimensions in the profile, which could be edited as if they had been created in Mechanical Desktop. This file, which was of average size and complexity, would have cost about $50 to convert using the Full Service option. Because the extraneous 2D data was not that extensive, using the Self Serve option would have saved only about $5.
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| Models converted by 2Dto3DCAD.com include features and dimensioned profiles that can be edited as if they had been created in Mechanical Desktop. |
Snap2-3D: Created by Manufacturing and Consulting Services (MCS), a developer of many CAD products over the last three decades, including its current product, Anvil Express, Snap2-3D is expected to be released this month. Because completed models end up as Anvil Express files, the program would seem limiting, but one innovative aspect of Snap2-3D is that MCS and Parasolid developer Unigraphics Solutions are working on exporting the converted solid as a Parasolid file with a feature tree. This would mean that users of any Parasolid-based program, including SolidWorks, Bentley Engineering's Micro station, and many CAM programs, could make full use of the features in the converted files. In preliminary tests, I found one unique aspect of Snap2-3D is that 2D drawings do not need to be cleaned up, as the software knows to ignore extraneous data. As in 2Dto3DCAD.com, Snap2-3D has a healer, but it seems to go further in making intelligent decisions about eliminating erroneous geometry.
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| Snap2-3D asks users to make decisions about conversions through the program's interface, in the top right corner of the screen. |
Xpand3D: Developed by MCS and based on a portion of its Snap2-3D technology, this $495 product will be offered in early 2001 by Unigraphics as an add-on for Solid Edge Version 9. When a DXF or DWG file is imported into Solid Edge, Xpand3D will create all the Solid Edge features in the 3D model. MCS and Unigraphics will continue to develop Xpand3D, which, when completed, will have the same functionality as Snap2-3D, except for the user interaction required to turn off the layer that contains any unwanted 2D elements.
Of all the existing 2D-to-3D conversion products, 2Dto3DCAD.com stands out in that it works as an ASP and is the only software that can deliver a model in several MCAD formats. However, there are a number of MCAD formats that 2Dto3DCAD .com and its competitors still can't provide. And even if MCS's plan to transfer feature information via Parasolid works as expected, there will still be a slew of other non-Parasolid products with which it won't work, such as PTC's Pro/E, Dassault Systemes' Catia, SDRC's I-deas, think3's thinkdesign, and Autodesk's Mechanical Desktop and Inventor.
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| Converting the model took less than 30 seconds, despite many small holes and other minute details. |
While there has been software for a number of years-from companies such as ITI, Theorem Solutions, and Spatial-that can convert 3D files from one system to another via neutral file formats, only recently have we seen the emergence of more robust 3D translators that can read in feature information as well. By extending translation capabilities beyond mere geometry, these new programs aim to greatly reduce the amount of time and money spent on rebuilding intelligence into a model. Here's an overview of some of the feature-based translators.
FeatureWorks: Developed two years ago by Geometric Software Solutions, FeatureWorks was one of the first feature-based conversion programs. Priced at $495, the software reads in neutral file formats (dumb solids) and builds features inside SolidWorks. Solid Edge and a few other MCAD products have also incorporated Geometric's conversion technology. And the company has written a feature-based translator for Pro/Engineer that has been used in SolidWorks and other products. In testing the Pro/E converter, I found that it does a good job on simple parts, but SolidWorks Corp. itself is the first to admit that on more complex models, a significant amount of manual work is needed.
Acc-U-Trans: Application Service Provider Translation Technologies Inc. offers its Acc-U-Trans translation engine to which users can upload files from Catia (version 4.19 through 4.23) or Pro/Engineer (versions 13 and up) for conversion from either format to the other. Once a file arrives, the Acc-U-Trans software translates it and checks it against the original file for discrepancies. If errors are found in the converted file, a CAD expert at TTI intervenes and, with the help of feedback provided by the software, resolves the problem. This "hands-on" approach is a powerful aspect of an ASP service, and is needed about 20 percent of the time, according to TTI.
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| Before: Here's a Pro/E model, complete with history tree, prior to conversion by TTI's Acc-U-Trans software. |
In testing this service, I received a rapid response. In fact, a Pro/E 2000 file I sent was returned the next day as a Catia 4.19 file with all the geometry intact. What's more, the entire history was preserved, even though Catia uses a type of history tree that has a totally different look and structure from that of a Pro/E tree. This would have been considered a typical translation, and would have cost $140. I also found the Web site to be user friendly, in that it allows users to check the status of their files.
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| After: The resulting Catia model retains the history of the original Pro/E file, making future editing possible. |
Proficiency Inc.: This company is claiming to have developed a universal product representation that will allow feature-based conversion between the "big 4" high-end MCAD systems: Pro/ Engineer, Catia, SDRC's I-deas, and Unigraphics. It will be part of a bigger collaboration system, which is expected to be available in mid-2001.
Powerful 2D-to-3D converters may provide the boost the stagnant 3D MCAD market has needed for some time because they can help 2D users worried about their legacy data make the move to 3D. The 3D-to-3D conversion market could also bolster sales, but the 3D converter developers have been slowed by uncooperative MCAD vendors who fear that if users could suddenly convert formats, a percentage of their customer base might switch to other systems and vendors. Despite the lack of support from CAD software suppliers, converter developers are making strides. If they keep it up, the interoperability problem will be solved with or without vendors' help.
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| TTI's Web site allows users to check the status of a translation, including whether the files are in process or whether they have been completed (shown above) or received. |
Joe Greco is a freelance writer specializing in computer-aided design. He can be reached at Joe3D@home.com.EMT · www.emtsoft.com
Geometric Software · www.geometricsoftware.com
Imagecom · www.aspire3d.com
MCS · www.mcsaz.com
Proficiency Inc. · www.proficiency.com
Translation Technologies Inc. · www.translation-tech.com
Unigraphics Solutions · www.solid-edge.com