Manufacturing

Move your Art to Part

1 Mar, 2000 By: Bill Stephens,Mark Huxley,Steven Weisberg

Moving from concept to digital manufacturing


One of the great attractions of adopting 3D solids-based CAD software in design and manufacturing companies is the promise of passing digital design files seamlessly among industrial design, engineering, analysis, and manufacturing applications. Art-to-part—the process of taking a design from concept through production in an entirely digital environment—becomes an increasing reality as technology and software continue to improve.

Manufacturing companies have pursued the art-to-part Holy Grail for more than 20 years, although use of the practice is in its relative infancy. One sobering estimate states that 85% of CAD work is still done solely in 2D. We will show that the digital process, when implemented properly, offers numerous benefits over traditional methods and only minor drawbacks.

The traditional product design generally consists of:

• sketching a concept and creating dimensioned
drawings,
• passing these to an engineer who interprets the drawings and creates engineering documentation of the part, and finally,
• handing the documentation off to a manufacturer who reinterprets and recreates the part.

This process often results in a final product that doesn’t reflect the original design intent. By creating and working with one digital 3D model from the initial design concept through manufacturing, you can drastically reduce overall time to market, eliminate unnecessary duplication of work, and maintain design integrity.

The digital model can shrink time to market by eliminating laborious drawings, letting you analyze and test the product earlier in the design cycle, and providing visualization and analysis tools not available in the traditional process.

To illustrate how this process can work successfully, we’ll describe how Volan Design , an international product development firm in Boulder, Colorado, recently helped to develop an oral healthcare product (figure 1) for Waterpik Technologies (www.waterpik.com), formerly known as Teledyne Waterpik. Volan Design was responsible for the industrial design of the product and also provided Waterpik with a 3D solid model for use in its engineering and CAD/CAM (computer-aided design and manufacturing) systems.

Figure 1. The art: A rendering of the finished Teledyne Water Pik Flosser and combination wall charger and stand.

Once Volan Design delivered the model, Waterpik engineers made final modifications to the design and passed it downstream to the manufacturing team.

Tools of the trade
For more than a decade, software vendors have offered product suites that claim to streamline and eliminate tedious development tasks. The newest software offerings from several vendors show great promise in making art-to-part a viable and seamless process. A software suite typically refers to a related, integrated group of applications, each of which offers a unique set of tools. These packages are rapidly evolving into more powerful toolsets that enable designers and engineers to improve the entire product development process. Such a suite, geared toward injection-molded plastic parts, might include:

• an electronic conceptual sketch pad
• an ID (industrial design) package
• a solids-based CAD package
• a FEA (finite element analysis) program
• a mold flow analysis package
• an injection mold design program
• a CAM (computer-aided manufacturing) program

These mainstream tools are further bolstered by packages that use the same solid model data to produce photorealistic images for use in marketing, create and show animated assembly or maintenance sequences, compute tolerance analyses, perform remote design reviews, and other useful functions.

To date, software vendors follow two approaches in software suite development. Some develop all of the applications themselves, which can negate the need for data translation. This tight integration is helpful, but can sometimes overburden development personnel. As a result, such software products often don’t evolve as efficiently as they should. Some software companies opt to provide an open API (application programming interface) that supports seamless integration among applications, masking the fact that several independent companies actually produce pieces of the underlying code.

Some product design companies have tried art-to-part but then shied away for reasons such as poor initial implementation, immature software, excessive capital expenditure, and insufficient training or the difficult learning curve for new users. Interestingly, Volan Design several years ago purchased an integrated product suite and found it too cumbersome. The integration simply was not mature enough to accomplish the required tasks. Volan Design now uses separate packages for ID and engineering, and the results are remarkable.

Design steps for sculptural products
A successful product development process requires accurate 3D visualization of the design early in the process. In the case of the Water Pik Flosser, Volan Design had to devise a method to allow universal access to the 3D design. Several transfers of the model data between Volan Design’s designers and engineers—as well as Waterpik Technologies’ design and manufacturing engineers—were scheduled to take place during the course of the project. Volan Design established a process whereby:

• (Art stage, part 1) The industrial designer created sketches, hand drawings, and rough foam models for initial concept generation.
• (Art stage, part 2) The industrial designer created a basic 3D computer model based on the foam models. It incorporated a specified drivetrain envelope provided by the client’s engineers.
• (Part stage) The mechanical engineer imported the designer’s 3D model and, using the ID surfaces as a template, created a detailed, manufacturable solid model for transfer to the manufacturer.

Industrial design modeling programs such as Alias|Wavefront, Unigraphics Studio for Design, and PTC’s CDRS are typically used in the second step because they let you generate models in a fraction of the time required by an engineering-class CAD system. Volan Design’s industrial designers typically use 3D modeling software created specifically for industrial design, not engineering software. Industrial design software tends to emphasize surface flexibility and accurate visualization more than time-consuming, mathematically precise engineering packages.

Users of ID packages don’t have to worry about radii, exacting locations, and similar issues. You can easily create and modify curves, surfaces, and shapes without suffering the repercussions of model history and parent-child relationships found in some CAD packages. In the early phases of design development, these features are better suited to the work. Once the model is transferred to the engineer, engineers use the strengths of the CAD programs to their fullest extent—namely, feature-based parametric design and integration with FEA and CAM.

Design goals and challenges
Dentists strongly advocate dental flossing as a critical regimen for maintaining healthy teeth. Yet research shows that only 1% of the population flosses regularly. Waterpik Technologies and Dane Robinson, D.D.S., set out to create a flossing product that people would find more appealing than dental floss and thus use frequently. The product was defined as a battery-operated flosser and released in January as the Teledyne Water Pik Flosser. The designers defined three design goals for the Water Pik Flosser. First, it had to be just as effective and easier to use than conventional floss and other flossing products on the market. Second, it needed a modular design that enabled custom product configuration for different markets and price points. Third, the device had to operate in a simple and intuitive manner for a wide range of people with varying dental requirements.

These goals presented a few design challenges. The flosser’s shape had to permit easy access to all areas of the mouth to accommodate children, elderly people, and those with special dental issues such as orthodonture. The product had to allow sharing among family members without compromising proper hygienic practices. Finally, the design team had to determine how the flosser would be stored, transported, recharged, and cleaned. A typical design requirement was that the shape of the flosser could not allow the flossing tip to touch the counter on which it rested.

Sketches and foam models lead the way
Waterpik Technologies and Volan Design conducted market research to help define the flosser’s specific features and functions. Industrial designers generated line drawings and sketches of the product that were used to make numerous handmade form study models (figure 2). The product development team then selected the most promising models for review in focus groups, which further narrowed the direction of the product design.

Figure 2. Designers experimented with various shapes before settling on the final choice.

At this stage, enough user information was available for Volan Design’s industrial designers to begin modeling the product on a computer, using the popular industrial design program Alias|Wavefront Studio. Designers downloaded internal component models of the motor, drivetrain, switch, battery, connectors, etc., from manufacturers’ Web sites, created them from specification sheets, and imported them from other CAD systems. The engineers adjusted the tolerances for Alias Studio to accommodate later data transfers to Pro/ENGINEER, the CAD program used by both Volan Design and Waterpik Technologies. They then created initial surfaces in Alias using the foam models as a guide.

Some complex projects, especially those where a team of designers and engineers work together, require that CMM (coordinate measuring machines) scan the model. This procedure, referred to as reverse engineering, ensures that each team member works from identical data. Designers can use the data as a guide or starting point in the industrial design and CAD packages. An individual or team can then work on any given portion of the project with the assurance that the controlling data points are maintained.

Volan Design then divided the form of the design model into pieces designed to accommodate molding and assembly requirements—a handle, with an over-molded soft-touch grip, to house the battery; two middle body pieces; and a snap-on hygenic sleeve (figure 3).

Figure 3. All elements of the Teledyne Water Pik Flosser assembly appear here in an exploded product view.

To help visualize the internal components, the model surfaces were viewed as translucent. Designers also used diagnostic tools within Alias Studio to ensure accurate geometry, tangency, and smooth curvature and to prevent interference with internal components (figure 4).

Figure 4. This rendering details the packaging of major product components.

The engineers then created preliminary renderings for design reviews that involved all of the people in the product development process. They exported preliminary surfaces in a format that Volan Design and Waterpik Technologies’ engineers could use with Pro/ENGINEER to study initial design feasibility. This approach let them start to refine and develop the assembly’s internal geometry. The initial engineering interpretations were used to build and test a prototype of the design. Because overall dimensions and estimated unit sales were known at this point, the design of the assembly line and packaging began. This work took place while the final external shape of the unit was still in development stages.

Design refinement
Volan Design and Waterpik Technologies incorporated design changes and refinements throughout the process. At one point, the decision was made to switch from two AAA batteries to a single AA battery to meet performance requirements and increase the duration of time between charges. However, the change also required a complete revision of the design. Designers modified and imported internal component models from their respective sources and digitally resized the product in less than one day. A change of this magnitude late in the development process would cripple a traditional 2D project.

Designers also used Alias Studio to create other related accessory components, including a wall charger for a rechargeable product version, a countertop stand, and a cartridge for replaceable flossing tips. Each of these accessories went through similar design processes and design reviews covering all aspects of their development.

In preparation for product design appearance renderings, designers generated appropriate background scenes, including bathroom tiles, a sink, and other bathroom products, to provide context and a sense of scale for the flosser. Designers imported product graphics and logos into the model and mapped them onto the appropriate model surfaces to provide a realistic depiction.

So that the marketing team could study a variety of colors, textures, and finishes, designers generated a detailed set of renderings. Alias Studio made it possible to modify each color and finish option in seconds and rerender them in minutes. This efficiency allowed dozens of aesthetic alternatives to be evaluated in a single day.

On approval of the forms, designers exported the surface models generated in Alias to Pro/ENGINEER. Transferring model data between systems typically involves some trial and error. However, once you develop standard practices, file import and export usually work quite well. Two standards normally govern this transfer: IGES (Initial Graphics Exchange System) and STEP (Standard for Exchange of Product Data). Both of these protocols have strengths and weaknesses, but both work well.

Once designers turned the surface model into a solid, they used Waterpik Technologies’ rapid-prototyping wax STL (stereolithography) machine to produce several physical models (figure 5). These models were an important step in the process because they let the designers evaluate a very accurate representation of the overall size, shape, and appropriateness of the product. These physical models were circulated to confirm that the final design was acceptable to everyone.

Figure 5. Rapid prototype wax models helped determine the optimal flosser shape.

Subsequently, Waterpik Techologies’ engineers split the model into its moldable component parts. They designed internal features to hold the motor, switch, battery, sealing features, etc. When they completed the internal component placement, the engineers produced additional prototype parts to troubleshoot and further enhance the design. Once the engineers were satisfied, they worked with Waterpik Techologies’ manufacturing department, which was responsible for the design and production of the plastic injection molds.

The manufacturing department used PTC’s Pro/NC, CAM software to program CNC (computer numeric control) machines to cut the steel for the molds. Finally, the molds were tested and tuned to produce the finished production parts.

Art-to-part disadvantages
The art-to-part process does have some drawbacks. Solid model creation can be time consuming. Occasionally, final details of the model may take an inordinate amount of time to create. File sizes can also get very large and slow down even the fastest of today’s PCs. The initial price and ongoing maintenance cost for industrial-strength PCs and software are also potential roadblocks to implementation.

A learning curve is certainly involved with the software programs used in this process. Obviously, the further along this curve the users are, the less time is wasted in experimentation. Another danger is that some software provides only basic or limited functions. This can tie the designer and engineer’s hands, making the job more difficult.

One potential pitfall is that photorealistic images created early in the design process can lead many clients to believe the design is farther along than it may actually be. Often, every photorealistic detail is taken literally, which can actually hamper the progress of the design process. Also, these images cannot address the ergonomic issues and touch-and-feel aspects of the product. To date, no substitute exists for building physical prototypes to prove out the design; however, in conjunction with accurate prototyping, 3D design software is the fastest, most accurate, and most powerful design tool currently available.

Art-to-part advantages
Despite the challenges encountered, a number of benefits make it worthwhile to use art-to part on a project such as this one.

Interactive 3D design. Flexible interactive manipulation of curves and 3D surfaces allows rapid exploration of design solutions and aesthetic forms that isn’t possible in 2D. The designer can manipulate the model by pushing and pulling directly on the surfaces in real time 3D. This is a critical advantage when working with today’s complex sculpted and ergonomic forms. Working in 3D also lets significant changes take place late in the design cycle.

Accurate visualization. Rapid photorealistic renderings give a preview of even the smallest details (surface textures, reveals, parting lines, etc.) much earlier in the process than was previously possible. These images tend to generate excitement about a product right away. The ability to rotate and zoom in on the model, rendering it from any angle, at any point in the design process, gives a much more accurate description of the product concept than even the best traditional 2D designer can provide. This improves communication among product development team members.

Detail manipulation. Easy slider-type controls let users manipulate colors, textures, and finishes to rapidly generate a wide variety of design options.

Diagnostic tools. Once the solid model is created, you can perform mold flow analysis, FEA (finite element analysis), tolerance analysis, animated assembly procedures, and more. Each of these tools can help produce better, more cost-effective products faster.

Design integrity. Because the product’s design surfaces are exported directly from the designer’s 3D model to the engineer’s software, the design intent and all subtleties of the form are included in the final product. In contrast, it’s difficult to accurately describe the complex, sculptural forms of today’s products using traditional 2D drawings.

Reduced time to market. This digital, 3D process helps relieve many of the frustrations inherent in traditional design and engineering. With this process, you can draft the sketches used to create the geometry. This reduces the amount of drafting time significantly because the person designing the parts is the one drafting the sketches.

The drawings and any subsequent changes are highly automated. Because the solid model can contain all the information manufacturing might need (fully dimensioned geometry, tapped hole details, surface textures, tolerances, etc.), fully detailed drawings are not necessary. If drawings are necessary, you can simply show the dimensions the engineer uses to constrain the sketches in a drawing. This could occur when the manufacturer who is awarded the contract needs a fully detailed drawing or when engineers must produce control and critical-to-function drawings.

This process reduces the time from concept to production and minimizes the inaccuracies of design interpretation that often frustrate designers and engineers. Though software companies have made claims of seamless integration between disciplines in the past, only with recent software innovations has this process become realistic for real world day-to-day product development efforts.


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Lynn Allen

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