Evan on Engineering Software

There is a whitepaper on PTC’s website that’s really caught my attention.

The paper, Explicit 3D Modeling: An Alluring Alternative for 2D Holdouts, talks about PTC’s CoCreate Modeling product in the context of 2D to 3D migration. (From what I can tell, all CAD vendors seem to believe that there are a lot of 2D users out there, just waiting for the right moment to buy their products, and jump headfirst into 3D.)

Irrespective of the whitepaper’s interest to 2D users, what was most interesting to me was the comparison of parametric modeling versus explicit modeling. (In the paper, PTC talks about "explicit modeling." This is PTC’s term for what some people also call "direct modeling.")

I suppose the reason I find this so interesting is that PTC’s real corporate name is Parametric Technology Corporation. They’re the folks who took the market by storm with Pro/E, the first commercially successful parametric feature-based CAD system. So, when they talk about parametric modeling and explicit modeling in the same breath, it makes me pause. And when they make a strong case for the advantages explicit (that is non-parametric) modeling, I have to stop, sit down, and make sure I’m not imagining things.

There is enough interesting stuff in this paper that I’m going to include some significant parts of it here. I’m going to skip the discussion of the benefits of 3D versus 2D, and just include the really meaty stuff. I’ve highlighted several passages in bold:

Explicit is different

There are two mainstream approaches to 3D design in discrete manufacturing -- parametric and explicit. With the parametric approach, designers use parameters, dimensions, features, and relationships to capture intended product behavior. Although the parametric approach is powerful, it does require expert knowledge about how best to embed engineering constraints and relationships within a model. With the explicit approach, on the other hand, designers quickly and easily create 3D designs. Then they modify the models through direct, on-the-fly interactions with geometry, so it’s flexible and easy to use.

Easiest to learn

With an explicit approach to 3D design, you only interact with the model geometry. Designers don’t have to create or maintain a complex recipe of parametric design features to produce model geometry. That makes initial training on the software easier. But it also means designers working with an explicit 3D CAD system can easily pick up a design where others left off -- much like anyone can come back and immediately continue working on a Microsoft Word document. So, explicit modeling appeals to companies with flexible staff, infrequent users of 3D CAD, and anyone concurrently involved in a large number of design projects. In terms of flexibility and technique, the explicit approach to 3D design is also quite similar to the 2D approach. That makes the explicit approach easier to learn because existing 2D designers easily transfer their skills and quickly adopt explicit 3D CAD systems. Designers don’t need to plan their designs in advance. Instead, they can let their designs evolve freely throughout the exhaustive design process, just as designers do when they work with 2D design. Plus, the explicit approach adapts certain 2D techniques to 3D modeling. For example, designers can move and stretch 2D geometry or even design within 2D cross sections of a 3D model.

Repurpose designs

With an explicit approach, companies have demonstrated accelerated product development by repurposing, or radically transforming, existing designs into new and completely different products. Customers of CoCreate Modeling give examples where 50% of parts within new product development are repurposed from previous designs. This unique characteristic of an explicit approach can shave weeks or even months from project schedules.

Stay open to change

Companies that develop new-to-market and one-off product designs often face changing customer and product requirements throughout the development cycle. An explicit approach is always open to change, so companies can keep the window open longer for new product information and major product changes. Rapidly evolve and explore designs Innovative product design involves exploration and discovery. An explicit approach gives designers the freedom to rapidly evolve a product design in unpredictable and new directions where modifications can’t be anticipated in advance.

Rapidly iterate designs

An explicit approach allows companies to rapidly test ideas, evaluate a broad range of options, and constantly adapt and refine a product as it moves through the development process. Companies benefit when they experiment with changes while changes are inexpensive and product designs aren’t locked into a specific development path.

Maintain flexible design teams

An explicit 3D CAD system frees any team member to contribute to and carry a design forward so companies can rotate designs between engineers to increase engineering productivity and eliminate resource bottlenecks or project delays. When companies rotate designs between engineers, they also create opportunities for higher quality and more creative product designs, because different engineers can both review the work and add their own perspective. Design responsibility is easily reassigned when different engineers or engineering teams become unavailable during the course of a project. For global companies, product development can move between different parts of the world as needed when anyone can contribute to and modify a design.

Work with multi-source CAD data

Explicit 3D CAD systems excel at the import and modification of multisource CAD data, benefiting companies working across an extended supply chain for procured components or subcontracted design. STEP and IGES are essentially native 3D design data formats in an explicit approach because explicit 3D CAD systems interact intelligently and on-the-fly with geometry and geometry is the only common element across all CAD systems.

Conclusion

For some companies that still rely exclusively on 2D design, the challenges and risks of adding 3D modeling to their design process consistently outweigh the benefits, despite growing industry pressures and clear advantages of 3D modeling. The explicit approach to 3D design, with its lower overhead and flexibility, tips the balance for those companies so that 3D CAD is finally a viable and lucrative addition. Once you’ve determined that the explicit approach best suits your unique needs, you can choose a 3D CAD system that will bring your company the biggest benefit and long-term success.

The key points that PTC makes here about parametric and explicit modeling are powerful, and hard to dispute. Yet, they might lead a thoughtful reader to an interesting conclusion: the best 3D CAD system for most companies could be one that offers both parametric and explict modeling capabilities.

It happens that the gold-standards in that realm are the new versions of NX and Solid Edge, from Siemens PLM. These support high-end parametric modeling, and, using Siemens Synchronous Technology, also support explicit modeling with intelligent feature inferencing and 3D non-history-based constraints. In short, a superset of the modeling capabilities that one would get if they bought both Pro/E and CoCreate. (CoCreate Modeling does have some feature inferencing, but, to my knowledge, does not support 3D non-history-based constraints. Actually, so far as I know, NX and Solid Edge are the only major CAD products to support 3D non-history-based constraints.)

I guess I’m still in a bit of disbelief here. I find it stunning that, despite all the discussion of Synchronous Technology in the media over the five or six months, the very best statement I’ve seen of its benefits is in a whitepaper authored by PTC.

Note: The passages I’ve included from PTC’s whitepaper are copyright 2008, Parametric Technology Corporation. They are used subject to the fair-use provisions 17 USC § 107, for criticism, comment, and news reporting.