An innovative approach to using CAD systems that was originally developed to simplify the design of automotive steering system parts has spread well beyond its origins and, through licensing agreements, can now help product designers in any industry speed up their design cycles.

For decades, the Delphi Steering Div., Saginaw, Mich., has been widely recognized as one of the most modernized, well-equipped, and efficient manufacturer of steering technology for customers such as General Motors, Ford, Toyota, and others.

But Ron Andrews, a senior product designer there, saw inefficiency in the way designers used their CAD software for designing steering system parts. The software let them create precise 3D models of a part, but making changes to these models — such as reordering, removing, or adding features — was incredibly time-consuming.

“In the past,” Andrews says, “our design group might be designing a plastic reservoir for a power steering pump and had to remove a flange. Making this simple change took a full day’s work.

“We had to move backwards through the model, menu by menu, feature by feature. That’s because features were built on other features, so changing one affected others. To make matters worse, we often destroyed half or most of the model in the process.”

After pondering that problem, Andrews and his design colleagues took on a new challenge: finding a better way to design parts so that they could be more easily modified. As a result of those efforts, the team succeeded in inventing a radically different, but simple, CAD modeling approach that was dubbed Horizontal Modeling (HM).

Before HM, Delphi designers, like designers everywhere, used the traditional method of feature-based modeling to create a part. Features were built on top of one another, in a vertical hierarchy. In this process, one feature, such as a hole, was associated with another feature, creating many “parent/child” relationships between the features.

The problem with this method was that, because of these parent/child dependencies, simple changes to any or all of the features were usually very complicated and often altogether impossible. Product designers were often forced to dismantle or completely recreate a model in order to make a change.

“This is still the method endorsed and taught by most 3D CAD software vendors,” Andrews says. “We call it the ‘hack and whack’ method of changing models. You have to hack and whack your way through the menus to see which features are related to each other.”

The team wanted to eliminate all the hacking and whacking, but at the same time, also wanted to continue using their current CAD software. So they decided to look beyond the standard techniques for using their CAD software and ended up creating a new paradigm—Horizontal Modeling.

With HM, designers can capture design intent without creating parent/child feature dependencies. HM enables rapid changes to any and all features in the model without the need for arduous dismantling and rebuilding of the design.

Comparing methods

The team realized that for HM to be fully appreciated and supported within the organization, they needed some credible, verifiable proof that it worked and provided significant business benefits.

They asked 70 Delphi product designers to use HM to create a new part that was nearly identical to one they had created in the past. The goal was to compare the total time spent using HM versus the “traditional” method. They found that with HM, Delphi product designers spent 20 percent less time creating models and 65 percent less time editing models. The proof led to acceptance, and HM now plays a key strategic role at Delphi, improving total design productivity by 35 percent and enabling many more projects without adding resources, and increasing innovation. HM is now in production use at 14 Delphi and partner sites worldwide.

The methodology

Fig. 1. CAD Creation of a casting model using the traditional vertical approach, beginning with a base feature and adding features on to it.

The new, simplified approach to using existing 3D CAD systems in product design departs from the traditional method of feature-based modeling, which stipulates the creation of vertical hierarchies of features with multiple, associated parent/child relationships between them. Simple changes to any or all of the features are usually very complicated and often altogether prevented.

Because of these parent/child relationships, CAD users and designers are often forced to dismantle the model to make the change, or recreate the model completely. While feature-based modeling has advanced the art of computer-based design, it remains an imperfect approach due to these inherent limitations in vertically oriented modeling strategies. Feature-based modeling has failed to adequately address the need for rapid design change propagation in downstream applications and processes.

For example, creation of manufacturing process models and process drawings from vertical feature-based models necessitates the creation of multiple, nearly redundant, non-associated process design documents. Each time an engineering change occurs, these unlinked process documents each have to be changed manually, wasting valuable time and resources.

Use of HM allows engineers to capture design intent without creating parent/child relationships, erasing the disadvantages caused by feature dependencies in product and manufacturing process design.

The illustrations showing the creation of a CAD model for a sample casting demonstrate the difference between the approaches, with the first three showing the traditional approach. In Fig. 1, the part begins with a cylinder shape as a base feature. A rib is added next, and then a pad, creating the chain effect that associates each new model feature relative to previous features.

Fig. 2. Feature list for the casting model showing the dependent nature of the features in the traditional approach.

As can be seen from the feature list in Fig. 2, all features created after the rib are dependent upon it.

Fig. 3. Deleting a feature in the traditional approach results in suppressing all subsequent features that were dependent upon it.

If the rib is deleted, it suppresses all the other descendant features, as seen in Fig. 3.

Fig. 4. Creation of a model using HM approach, showing how the features are referenced to user-defined coordinate system, rather than to each other.

The other three illustrations, Fig. 4, 5 and 6, show how this would work with a Horizontal Modeling approach. With HM, datum construction planes are created through the default coordinate system to establish a user-controlled, absolute coordinate system. In Fig. 4, the cylinder base feature is defined in reference to the coordinate system. When the rib feature is added, its placement is defined in reference to the coordinate system, and not to the cylinder, so the rib is not dependent on the base feature that preceded it. Additional features are added in the same manner.

Fig. 5. Feature list with HM approach shows how they are not dependent upon each other.

As a result, when a feature is selected for deletion, as shown in Fig. 5., it is referenced by its defining datum planes, not by relationships to other features on the model.

Fig. 6. Casting model shows how removal of feature in HM approach did not affect any of the other features.

Therefore, when the feature is deleted, as shown in Fig. 6, it is removed from the model without affecting any of the other features, thus eliminating the need to recreate the model all over again.

The HM methodology allows designers to work from fewer CAD models, which streamlines the product design process, raising productivity, enabling faster updates and changes, and automating downstream flow of process documentation for manufacturing. Delphi says that use of HM measurably lowers product and process design costs, while shortening design lead times, reducing waste, and boosting the efficiency of countless downstream applications, all resulting in higher productivity and faster time to market.

HM can also improve data and design quality. By streamlining the design change process, more ideas can be tested at lower cost, which results in higher quality design concepts and less wasted material and time, within a naturally occurring “lean” design process.

Reduced costs

Delphi reports that one Delphi product team was staffed with 18 in-house CAD operators and 16-18 outside contractors for a particular design. Using HM, the next design required 14 in-house CAD designers, and no outside contractors, representing a 60 percent reduction. If product designers cost $110,000 per person/year (fully costed), this represents a cost savings of $2,420,000 on this design team alone in a year. HM allows designers to take on more projects without increasing resources, eliminating outside contractors while handling their existing workload, and greatly increasing their overall productivity.

For product designers using HM, Delphi measured a 20 percent reduction in time for creating models and a 65 percent for editing models, compared to the traditional vertical modeling approach.

Shorter lead times

Delphi designers and engineers also measured noticeably shorter time-to-release for the product designs into manufacturing. By enhancing concurrency between product and process design phases, they measured a 50 percent reduction in process drawing creation time, which reduced lead times three-fold to four-fold, while completely eliminating costly detailing work.

Less waste

The improved data quality and structured HM methodology also aids lean design and manufacturing practices. During testing and implementation throughout Delphi, it was found that all product designs created using HM were 100 percent usable in downstream applications. Prior to implementation, a model was typically only 0 percent to 10 percent usable, which meant that 90 percent to 100 percent of the data had to be recreated manually.

As a result, the HM methodology delivered a 76 percent reduction in model detailing and process model-creation costs, consistently throughout the Delphi organization. In addition, time required to create process drawings was reduced by 80 percent to 90 percent.

Before HM, every designer had his/her own way of doing things, making it difficult for a designer to get up to speed on CAD files created by another designer. Now, because everyone uses the same HM methodology, coordination is faster, design intent and details are already understood, and changes can be made very quickly. This lets people move around to different projects more easily, providing much greater flexibility in staffing.

In an effort to help product designers learn how to employ the HM approach, Delphi Technologies, Troy, Mich., is licensing the patented methodologies to CAD training schools and organizations to train product designers. Licensing partners currently include CADPO, Westminster, Colo.; SCATE Technologies, Orion, Mich.; and CADVenture, Willoughby, Ohio. Further licensing arrangements are also in the works.