Machine Design

Redesigning the design department

Useful additions to CAD software are coming so fast, it makes sense to rethink design workflows.

Andrew Anagnost
Autodesk Inc.
San Rafael, Calif.

The concrete busting machine from Sweden-based Brokk was modeled and analyzed for its range of motion in Autodesk Inventor. Features in the software help minimize errors and improve overall product performance, for example, by letting users reposition the boom to different positions.

Sulzer's Harris says he sends realistic representations of new pumps, such as this one, to customers to show how the equipment fits into assemblies. The 3D models are accurate and easy to understand for shop-floor people and customers alike. The actual build appears below.

The structure has been analyzed for displacements using Ansys which is embedded in Autodesk Inventor Professional. The FEA calculates stresses, displacements, and safety factors based on userdefined loads and geometry.

The wiring diagrams on the left were designed AutoCAD Electrical, software that lets electrical engineers detail wiring schemes and controlsystem diagrams. Changing the diagram can update the wiring model in the enclosure to the right if it were modeled in Autodesk Inventor Professional.

Trying to visualize the casting from the 2D drawing could give a designer headaches. But modeling it first in 3D solids and letting 2D CAD software generate the drawings makes more sense. Autodesk 2004 can read Inventor files to create front, side, ISO, detail, section, and auxiliary views with automatic retrieval of model dimensions.

Autodesk Inventor lets users create and modify pipe routes by selecting a start point and end point, and any number of intermediate points to define the route. Associativity with drawings means that pipe routes are updated when the 3D assembly changes. What's more, a rulesbased feature configures the model to company standards, such as minimum or maximum lengths and bends.

Workflow in engineering departments just a few years ago was not exactly a model of efficiency. A large part of design engineering was an exercise in developing 2D drawings from 3D models. Development cycles depended on a sequence of isolated activities completed by several discrete teams. Drawings passed from department to department, and eventually someone checked them for tolerances, motion interferences, weldments, tubing, and wiring.

This compartmentalized department meant a backand-forth process took place across several teams (mechanical, electrical, plumbing) working on various parts of an assembly until each discipline was ready for manufacturing. And it could take weeks to months and was often late to manufacturing.

Bringing specialists, such as finite-element-analysis experts, into product development has produced mixed results. On the up side, advanced technology (FEA and kinematics) has helped specialists spot weaknesses and interferences early on. On the down side, sequential-design processes create silos of effort with enormous potential for discrepancies, errors, and delays. For example, it could take a design tossed into analysis two weeks before the model is built, analyzed, and the results made available.

Even now, members of extended development teams, such as electrical engineers, often don't get their hands on a design until late in a cycle. Surprisingly, electrical controls are often not even considered until products reach the shop floor.

It's not a pretty picture for design firms, but there are solutions. One traditional method for speeding up work has been to punch holes in the walls separating design-team members so communication and information flow more easily. The idea has always been right but what passed for advancedengineering software just a decade ago was not ready for prime time. It was underpowered, expensive, and only ran on Unix boxes.

The most recent crop of design programs, however, lets all disciplines work as a well-connected team regardless of location. Here are a few of the new features that can boost the efficiency of a design team.

Take the simple mirror command, for instance. It helps build symmetric parts by letting users construct half while the CAD system generates the other half. Now imagine extending that to symmetric assemblies, such as hydraulically powered machines, with hundreds of parts and subassemblies.

Building just half the assembly with dozens of cylinders, motors, and hoses can take days. But a CAD program can build the other half in seconds with a complete bill of materials. This feature can cut days off design budgets and substantially boost department efficiency.

Interference in most assemblies is almost guaranteed. But CAD modelers can spot interferences and eliminate timeintensive redesigns that correct errors uncovered in physical assemblies. Interference checking alone gives manufacturers several ways to update designs.

Welds, frequently encountered and time consuming to design features, could be ready for automation if they are designed to standards. But there are hundreds of standards. If all the standards can be coded into a CAD program, however, drawings or models of large welded structures could be made in a fraction of the time previously possible.

Analysis and simulations provide additional opportunities to improve designs. Technology exists today to bring simulations, such as finite-element analysis, kinematics, and motion studies, directly into CAD programs. FEA has been tamed by many developers so that designers can take first-cut analyses of structures without transferring models to separate programs. Just one capability in FEA lets it pinpoint weak (high stress) and overdesigned areas. Other FEA capability looks at the flow of heat through a system, and modal or vibration analyses.

Kinematics, on the other hand, can bring mechanisms to life, show ranges of motion, and pinpoint what will collide and where. This helps push products more quickly through the physical prototype stage.

Collaboration between widely dispersed teams provides another way to slice time from design budgets. Users at separate locations can examine the same model online, suggest changes, and make adjustments that would have required business trips in previous generations. The effort leads to fewer engineering changes as designs approach the production line.

Version tracking and vaulting or storage features in CAD software can ensure designs created with accurate data can be reused without losing design integrity. Such capabilities make it possible to tap into the wealth of data in a design vault. What's more, sharing high-quality work fosters greater collaboration.

Document sharing and collaboration work even better when the Web is involved. Renderings in 3D and engineering documents can be posted to a Web site for others in the supply chain. The technology still lets engineering departments retain a degree of control essential when sharing proprietary and sensitive information.

With technology that lets designers, electrical engineers, and others work from the same CAD program, expect to see the walls separating their cubicles come down, at least in a virtual sense. This will probably happen when 3D models are the conduit for engineering detail. Models in 3D, for example, show how 2D drawings from different disciplines work together, a necessity that previously was quite difficult. With common technology for creating, managing, and sharing designs and underlying data, engineers will be able to collaborate early and frequently throughout product-development cycles.

Standardizing on 3D CAD

Like many manufacturers, Sulzer Pumps, Portland, Oreg. (, wants to improve communications among its worldwide design teams, trim its development cycles, cut costs, and improve communications with customers. To address the challenges, the manufacturer decided to standardize on one CAD system for product packaging, and move from 2D to 3D model design.

The company eventually chose Autodesk Inventor because it helped cut design and manufacturing costs by letting design teams reuse portions of drawings in new projects, and integrate legacy models of piping interiors created in Unigraphics software by other teams in the company.

The decisions also improved communication with customers and shop-floor personnel. "Models in 3D are so much easier to understand than flat 2D designs. Even nonengineers can understand how a large pumping system fits together," says Jeral Dee Harris, CAD designer. "Overall, we have increased our competitive advantage by improving product quality, shortening design cycles, and improving communication with customers," added Harris.

Autodesk Inc.,
(800) 435-7771,

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