Getting from There to Here with Integration Guard DCV
Mike Hudspeth posted on November 30, 2016 |

Anyone who has worked with 3D CAD models for very long has had to deal with imported models from outside sources. You will have had to import files and try to do something with the resulting data.

Sometimes it’s easier than other times. Some models come across the great digital divide with few problems and bring with them very useful geometry. Other models, not so much. Sometimes you are working with a vendor who has their own CAD system, not the same as yours.

You still need to make use of their data. Translators have gotten very good at getting 3D geometry from one CAD program to the next. But despite their many promises of vast functionality, they somehow seem to fall short of the mark. No matter what translator you use, almost invariably, you are left with an unparameterized block of digital stone—a dumb solid.

Gone is the feature tree that captured the design intent. Gone is the ability to make changes simply by editing a few key dimensions. Gone is any sense of control you might have imagined you possessed over your design data. In short, you’re helpless. Or are you?

Here’s the problem: You have a model that describes your design (or at least a piece of it). It doesn’t matter where the model came from, whether it originated with you or someone else at some other company. What matters is that you have it and need to make some changes. For whatever reason, timing, workload or, say, relative skill level, an outside vendor or customer updates the model.

Here’s the rub: The sender doesn’t use the same 3D CAD software you do. When the work comes in, it’s a STEP file. No problem yet. You import the file into your 3D modeling software. That’s when the fun begins. Right away, you notice something has changed. Sure, you already knew what you expected to change—and it did. But there is something else that is different. You can’t put your finger on it but you know the vendor did more than you were expecting. Now what do you do?

Some software packages can compare models and tell you what is different. They most often do this by superimposing one model over the other and highlighting the areas that differ. Some will even create solids that describe the changes. But just knowing what changed is only part of the issue. How are you going to incorporate the changes into your design process?

A lot of companies will spend inordinate amounts of time querying the model to see what changed and how. Then, they will go into their model and parametrically recreate the changes. Time is money and that sort of activity is therefore inherently expensive. But it’s necessary. Why? Because of how most modern parametric modelers describe their geometry.

There is a thing called a face ID. It is a name assigned to each face of the model. (In fact, each face, edge and vertex has a unique ID.) Say,for instance,you have a model of a cube. That seems straightforward—six faces, right? Now, you ship your model off to your vendor to machine an injection mold.

The first thing the vendor is going to want to do is add draft. That will slightly change your model’s faces. The vendor adds a fillet to one edge. This will add a new face and therefore a new face ID. But, frequently, this can also reshuffle the rest of the model’s face IDs.

Now, when you import the new solid back into your assembly, the mates will fail. If you had CNC tool paths they will fail too. Why? Because these functions reference face IDs to do what they do. When the face IDs change, the software doesn’t know where to apply the mate or tool path. You are left with a lot to fix. And repetitive manual updates take forever! Not to mention, they also introduce the very real probability of error.

“Associativity is great—until it breaks.” – Peter Kirkwood, Integration Guard 

A company called Integration Guard has come up with a pretty neat way to handle model updates. Its software, called DCV(Design Change Vector), has a new approach to mapping out changes that might otherwise complicate your world. DCV recognizes the differences between the two solids, then maps the identifiers (face IDs and such) from the previous version to the current version.

The cyan faces are matched. The blue faces are proposed matches.DCV found the extra added hole (white face) because it didn’t match anything in the new file.
The cyan faces are matched. The blue faces are proposed matches. DCV found the extra added hole (white face) because it didn’t match anything in the new file.
DCV compares the raw B Rep geometry, like other software, but it is smart enough to recognize that, although the model has changed, the faces are not wholly new faces but merely the same faces slightly altered. It then matches face to face and reconciles the face IDs to provide stable identifiers for integration. Now, your mates won’t explode.

DCV works both as a standalone program and as an add-in for your favorite 3D modeler of choice. Integration Guard partners with software vendors to make sure DCV will run in their software interfaces. DCV is thus designed to work with a wide range of software—probably even yours. Translators are generally aimed at taking files from one specific program to another.

There are other capabilities DCV brings to the table. You can tag each change to its own ECO.That way, you can track what was changed when.

DCV allows you to associate each change with a specific change order so you can not only see what changed, but by what authority. That makes tracking your changes very easy.
DCV allows you to associate each change with a specific change order so you can not only see what changed, but by what authority. That makes tracking your changes very easy.
DCV can even update your finite element analysis (FEA) data and tool paths.
DCV will update your FEA shells, saving you time and effort because you don’t have to do it yourself.
DCV will update your FEA shells, saving you time and effort because you don’t have to do it yourself.
DCV will update your tool paths automatically.
DCV will update your tool paths automatically.
Look, in the real world, things don’t always work the way we’d like. Companies are bought and sold, and you must use data from other software packages. Things can get a little crazy (okay, they can get a whole lot of crazy).But with a program like Integration Guard’s DCV (priced at $1,800 per seat per year), things can be a whole lot more sensible. You can visit the Integration Guard website for more information or to arrange for a license of your very own.

Integration Guard has sponsored ENGINEERING.com to review this product. It has provided no editorial input to this review other than verification of the technical facts. All opinions are mine. —Michael Hudspeth 



About the Author

Michael Hudspeth has been a designer for over two decades, a lifelong artist, an avid model builder and author (specializing in science fiction). He, his wife, two daughters and one too many cats thrive in the great American heartland, just outside of St. Louis, Missouri.

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