CAD Doctor workflow

1 ' Our STEP file when imported into SolidWorks (as is) shows a number of errors - so we use CAD doctor to clean up the geometry and prepare it for translation.

2 - Checks were run on the STEP file - in this case, we're looking to move the data to SolidWorks. The initial check gave us a whole host of errors, one minor (relating to acute face connection), a total of 41 serious errors (ranging from intersecting loops, through short curves and into gaps between edge and base curve).

3 - The auto-stitching tools were run, which cleared up the short curve problems. Looking into the gap problems, the system offered a range of tools to fix the error, from refitting the face to the loops, extending or recalculating the surface as well as some other options.
Using the Fit Face to Loop, we were informed that the cap was 0.0004mm so we hit ok and the gap closed up, and the error disappeared.

4 - We worked our way through the various errors, fixing each individually (just a few button clicks in truth) and the end result was a part file ready for exporting and reading into SolidWorks. The export options allow you to output STL files (either binary or ASCII), Parasolid or IGES. While SolidWorks is based on Parasolid, we thought we'd go for the less easy option and export it as an IGES.

5 - the end result in SolidWorks. Running the Import Diagnosis tools show that there are no problems at all

With its background in the world of data translation and exchange, it will come as no surprise that Elysium’s CAD Doctor is a system tailored to that exact process – of moving geometry between different CAD systems. While other systems concentrate on the provision of tools for dealing with the likes of IGES and STEP-based data, CAD doctor’s remit is a little wider; it also allows you to read in data from a variety of native formats.

Once you have read in your data, the next task is to identify the target system. What this does is adapt a very lengthy list of parameters and variables to create a customised list of requirements for data to be read into Catia V4 and V5, I-deas, Pro/Engineer, Unigraphics/NX (Parasolid), SolidWorks, TopSolid, Solid Edge, Inventor (incl legacy support for MDT), OneSpace Designer and CADCeus. What these presets do is tailor things like tolerances (for angles, shortest curves, merging of points, etc), then check that the part must pass in terms of topology and geometry (such as intersecting loops, free edges, gaps, small surface patches and the like). You can also create a list of parameters for a custom system if it’s not supported. The goal is to ensure that when the part is read into the target system, there aren’t any errors and things go through perfectly.

Of course, as most of us know, data exchange is a troublesome process, so once your part is read in and the target system is defined, the next stage is to run the check. This performs an inspection of your part according to the target system parameters you’ve set. Depending on the complexity of your part and the number of errors found, this can take quite a while.

Once it’s complete, the results are displayed in the Status window, as this categorises the errors found in the part file according to their type. I ran tests on two part files. The first, a relatively complex steering wheel part (exported as IGES), contained hundreds of errors, while a cylinder head contained twenty or so. In addition to listing the errors, the Status window also display a severity factor that ranges from Minor, Serious to Critical – essentially, minor is a small error that won’t have much effect on the translation, while the other two will.

Error fixing

Now that you have a list of errors within your part, the first port of call is the automated tools that allow you to both stitch then heal them within tolerance. These should sort out a lot of the most common problems found within your model. As you iterate through the commands (gradually increasing the tolerances at each pass) you should see some of the error counts reduce. Obviously there’s a trade off between slackening off the tolerances and the changes that the process will make to the underlying CAD model – this is something only your organisation and specific needs can control.

Now, the automated stitching and healing tools can handle many errors, but the chances are that you’ll be left with a few tricky ones that it can’t deal with. This is where the manual inspection and fixing tools come into the picture. When you select a category of error, the system provides you with two strips of icons below the model tree window. The icons to the left allow you to flick through each error and zoom into it so you can see exactly what’s going on. Here the toggle model will come in handy as it allows you to swap between the whole surface model and just the surfaces that are influenced by or causing the error.

When you select a specific instance of an error, you’re also presented with a number of fixing tools for that particular type of problem – and only those tools available to solve those problems – which makes life much easier for the casual user. You can try out different fixes, but after a while, you start to get a feeling for which fixes solve which problems, so you can blast through it pretty quickly.

The Toggle Display switches from the full surface model to display just the curves and surfaces that are influencing the error you're working on.

Once you have your data repaired, the final stage is to export it to your target CAD system. The export options allow you to output STL files (either binary or ASCII), Parasolid or IGES. While SolidWorks is based on Parasolid, we thought we’d go for the less easy option and export it as an IGES. The system does filter out the export options, so you only get options for your target system.

In conclusion

In MCAD, we’ve discussed the problems associated with 3D data translation on many occasions and looked at a wide range tools available to repair such problems. I’ve not seen Elysium’s CAD doctor before and have to say that I’m impressed. The system is single minded in its focus and as a result has several benefits. Firstly, the interface is streamlined, so that it only provides you with the tools you need to inspect, report on and resolve data translation issues, and as such is very easy to get up and running with. This is essential for those users that won’t be using the tool on a daily basis as it’s easy to pick again after a break. Secondly, and perhaps more importantly, the system works pro-actively to ensure that the options you’re presented with relate to the task in hand, and the simple selection of the target CAD system does a lot of work under the hood to adapt the system’s goal to your needs. This is followed through the system with the filtering out of unnecessary operations and functions when you don’t need to use them, making it very intelligent and again, easy to pick up without having to delve into the manual too much.

The CAD vendors are unlikely to resolve the issues surrounding data translation and the headaches encountered on a daily basis by a large portion of the CAD using community look set to continue into the foreseeable future. It’s only with systems like this that you can get a helping hand to ensure that when you do conduct data translation tasks, the pain associated with the process is removed - allowing you to get on with the job at hand, designing and developing new products.