Machine Design

Rapid Prototyping Accelerates The Design Process

Engineers need to adopt new habits to make the most of rapid prototyping.

G. Thomas Clay
Z Corp.
Somerville, Mass.
Preston G. Smith

Certified Management Consultant
New Product Dynamics
Portland, Oreg.

Rapid prototyping has been a tool in the designer's arsenal for over a decade now, and the technologies behind it have improved greatly. The main impact of these technologies, however, has been to replace traditional modeling techniques in the final stages of product development and the transition to manufacturing. But the greatest potential for 3D modeling lies earlier in the design process where superior designs are conceived and the roots of development delays are put down.

Properly used, rapid prototyping can greatly accelerate product development and lead to high-quality, defect-free products. Fortunately, the new generation of rapid prototyping tools, variously known as conceptual modelers, desktop modelers, and 3D printers, are much faster than earlier versions. They lend themselves to use by engineers in office environments.

Traditionally, rapid prototyping (RP) has helped engineers shorten the design cycle by letting them make in 2 hr a prototype that would have taken a week without it. Such a savings in time is impressive on a percentage basis, but the week saved is meager compared to the typical 12-month development cycle.

To really save time with RP, managers and engineers need to update the product-development process to reflect the power of next-generation RP tools. And to trim the most time from that process, they should examine the slowest parts of it with an eye to applying RP's potential to radically accelerate these activities. Ironically, the biggest opportunity to save time is before most companies even start their clocks — the fuzzy front end prior to concept approval. Few firms are aware of the large amounts of time that slip by unnoticed in that fuzzy front end.

Many companies conveniently define the conceptual stage out of existence — or more precisely, out of their minds. They simply define the start of a development project as when they have approved a concept. But the internal milestone of concept approval is immaterial to the marketplace and the competition, which start their clocks when the market opportunity arises. There are several ways companies fritter away precious time prior to concept approval.

Delayed decision making. Later stages ofthe design process have well-defined decisionpoints with clear, objective data on which tobase decisions. In earlier stages, however, theprocess and the data are all softer and relevantparties to the discussion may not have a common base of communication. It might not evenbe clear who the relevant parties are.

Lack of a common decision-making medium. Those involved in key decisions — marketers, engineers, manufacturing staff — maynot have convenient access to the same, commonly understood product information.

Lack of communication. Design processes can wander with too many or too few possibilities being investigated. A sensor company recently found that the different segments of its design team, which are located in different states, were each pursuing ideas subtly incompatible with concepts evolving at the other sites. After these different branches of development grew apart for several months, the groups had a dramatic shock when two of the three groups were forced to perform substantial redesign to be compatible with the third.

Lack of consensus. Those involved in the design process may disagree on which direction to take with a product. In many cases, designers develop strong ideas about which way the product should go. They are often limited to debating relevant advantages based only on CAD drawings and 2D renderings. The relevant arbiter of the discussion, the customer, can't be brought into the discussion to offer input and settle the issue in a practical way because customers usually don't relate well to drawings or renderings. This leaves the decision process resting solely on personal opinion, which could deadlock the project.

Changes in direction and rework. Critical mistakes often survive unnoticed in digital models for weeks and only appear when a project approaches production. One project, for example, was held up for a month when someone finally detected that a late-stage change made to internal components would force a rerouting of the wiring and cause a onemonth delay. This problem existed in the digital data for weeks but was only found when the project went to late-stage modeling. If the rewiring conflict were caught earlier, the delay could have been avoided completely.

Sometimes it's the end customer who finds amistake late in the process. On a design projectfor a handheld medical device, the basic grip design was tested by several nurses late in theprocess. The grip turned out to be extremely uncomfortable if held for several hours, a long butnot unusual period of use for the tool. This leftthe design team to choose between delaying theproduct release for weeks or going to marketwith a product that would appeal to only 75% ofthe target market.

Three-dimensional prototypes put engineers, managers, manufacturing staff and marketers on equal footing in evaluating designs. All the interested parties can see, touch, and handle the design, just as the ultimate customers will.

Some companies take the extra step of including end users in the process by using prototypes. One product developer, for example, prototyped 12 different concepts of a handheld device in one day then convened a test panel of likely users to evaluate the design. They identified the best features from each, and the company quickly created a hybrid that captured them.

Prototypes also clarify communication, spanning distances and disciplines. For example,Graco Children's Products, a leading manufacturer of child-safety products, uses RP to communicate between its design facility inPennsylvania and its production facility inChina. A leading automotive company uses RPto communicate between engine designers andthe foundry.

Adidas uses concept models to rapidly create new sole designs and then immediately broadcast these models around the world to sister facilities. They e-mail CAD data and prototypes are "printed" at the remote sites, creating a "3D fax" capability.

Prototypes are also effective project-management tools. On a recent project, a sensor designcompany produced prototypes after each designiteration. They sent copies to the marketers,management, and a focus group of end usersseveral times each month. This let designersstay close to the customers' needs while lettingmanagers closely monitor the project'sprogress. Management and marketing met toreview options and establish a given directionfor designers, along with goals for the next review. Regardless of technical training or accessto specific hardware, each member of this design effort had the same information at thesame time in the form of the 3D prototype.

Prototypes also are handy at design reviews.The prototype need not embody all of the product's final qualities; it is only important themodel convey information clearly. At a recentdesign review for a component on an upcomingMars lander, for example, a working prototypequickly drew attention to problem areas such asa piece not thick enough to survive the landingimpact.

Other companies, like ExpressCAD, a designservices firm, use RP to force a project along. Inone instance, ExpressCAD used RP to go frominitial concept for a skateboard wheel assemblyto finished parts in just 10 days. They placedthemselves on the regimen of a model a day,and at the end of each day, new models were delivered to the client. The client sent back theirreactions and gave ExpressCAD an idea ofwhere to focus the next day's activities.

Most companies can't see final designs inproduct form until tooling is produced. Newconcept-stage RP technologies can providedozens of snapshot views of the final product ata fraction of the time and cost of traditional RPsystems. This lets designers watch as the product evolves and lets them take more chancesand be more creative as less time, effort, andego are invested in each model.

For example, engineers at Giostyle, aEuropean housewares manufacturer, use RP tofully explore a wider range of possibilities."Many other companies are trying to reach thesame customers we are, and some have farlower labor costs. If we are to succeed, we mustgive the customer products that are clearly better and to do so we must be more daring thanthe rest. Concept modeling helps us do that,"says a company spokesperson.

A major company in the handheld communications market also uses RP to accelerate creativity. Rather than following the normal practice of prototyping only until the major design direction is established, they begin by turning out 10 prototypes representing ten different design approaches. They solicit feedback on these and select the best features of each, and then turn out a new series of hybrid designs in just a few days. As they describe it, they give themselves "the luxury of presenting customers with a variety of possible combinations and gaining early insight into niche-focused concepts." Rather than taking leaps of faith toward their customer's preferences, they pursue what they call "the scientific process of design."

The examples above only scratch the surface of what can be done with RP to improve and shorten product development. Here are some suggestions for helping other companies change their design styles to take full advantage of RP:

Every prototype should be aimed at aspecific question that needs answering.When RP was expensive and slow, engineerscould only afford to use prototypes that testedseveral ideas at once. Now they can afford totest ideas individually, then mix and matchlater. Consequently, to assimilate this new behavior, explicitly plan to use each prototype totest only one idea or assumption. It's good scientific practice to test hypotheses independently, and now engineers can afford to do it.

Prototypes should be only elaborateenough (strength, surface finish, etc.) toanswer this question. In later stages of development, where models have traditionallybeen cost justified, designs were mature andwell refined, so refined models seemed appropriate. When models are used early in the product-development process, such refinement iswasteful. Engineers should build prototypeswith just enough detail to answer the specificquestion at hand. When you have this answer,toss the prototype away and move on. This prevents money and time from being wasted polishing models in ways that won't move the project forward.

Be advised that everyone, including the accountants, will have to get used to seeingwastebaskets full of models that have servedtheir purpose. To help you with this, you mightconsider the much-ballyhooed paperless society that computers were to bring us. So far, paper usage is actually rising. Why? Because wecan produce high-quality documents more easily and at much lower cost than ever before,and these documents help us run the businessmore effectively.

If you think of multiple alternatives, build multiple prototypes in parallel. Everyone is aware of the speed advantages gained by proceeding on multiple activities in parallel. Now we can afford to do it with models. If designers or engineers think of alternative ways to solve a design problem, make prototypes of each option rather than presupposing the best solution and modeling only one. With prototypes of the alternatives, new combinations may become apparent.

Make decisions as questions are answered. Don't wait until the final prototype appears. This is probably the most difficult habit to change, but it is also the most crucial. This change will affect others in the organization, such as marketers, people in manufacturing, and top management.

The trick to progressing quickly with RP is tomove forward incrementally with small butsound steps. But if the final decision makerscontinue to wait until the final, "perfect" prototype appears before making any commitments,there will still be lots of second guessing, indecision and rework. And there will be no real improvements in the process. This behavioralchange is essential if RP is ever to grow beyondthe "cute toy" stage.

The faster you can make prototypes, the faster you can develop the product. Making the best use of RP is predicated on making small but sound steps quickly. Thus, the process accelerates to the extent technology will let us make and assess models more quickly. But it won't work if a company still makes conceptual prototypes by sending them out for processing at service bureaus, still ships prototypes to decision makers the same way they used to, or management still takes as much time to make decisions as before. Success depends on the ability to shorten the iterative product-development loop.

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