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issue: July 2008 APPLIANCE Magazine

CAD/CAM and Rapid Prototyping
When Speed Is of the Essence

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by David Simpson, Contributing Editor

Advances in rapid-prototyping technologies and CAD/CAM are speeding product development and even enabling low-volume rapid manufacturing.

This Alias software image by Montgomery Design International was the forerunner of a series of room air-conditioners produced by Amana and sold under the Amana brand and as an OEM product under the Kenmore brand. It is an early example of digital prototyping that was capable of showing various features of the unit as well as the overall styling and design. In some customer reviews it was morphed into a natural setting to give a more realistic product view.

Accelerating product development cycles are being pushed by factors such as global markets and fickle customers. But product development acceleration is also being pulled by the available development tools. Fifteen years ago, 3-D computer-aided design (CAD) and rapid prototyping (RP) were in their infancy. These tools were not widely used in the appliance industry and tended to be expensive and to have limited capabilities.

Fast-forward to 2008, and an entirely different scenario presents itself. RP models that used to be brittle and monochromatic can now be made in multiple colors or with properties that even allow functional testing. CAD and CAM (computer-aided manufacturing) capabilities are also much improved, thanks to years of software development and the harnessing of ever-cheaper computer technology.

These kinds of product development tools are becoming the norm. Their usage presents opportunities for OEMs to speed up design cycles, while reducing the risk of last-minute tooling revisions. But they can be seen as something of a double-edged sword, since they also increase competitive pressures to accelerate development. Even if your company does not use them, your competitors may.

New 3-D Growth

CAD systems are a central component in faster product development. Today there is widespread penetration of 2-D CAD systems. Meanwhile, advanced parametric 3-D CAD systems, first introduced around 1990, are becoming more common. A 3-D system enables the design of solid models that can be rotated on a computer screen. While a 2-D CAD system relies on the user to enter dimensions, a 3-D system works with parameters, such as curves or holes, and automatically updates properties and dimensions. This parametric capability speeds product design and improves software ease of use. In addition, a 3-D CAD system can interface with rapid prototyping machines by putting designs in the STL file format. This transforms the design into virtual thin cross sections that can be progressively produced in an RP machine.

“We see 3-D CAD as already accepted by innovators, early adopters, and some of the early majority,” observes Greg Milliken, CEO of Alibre Inc. (Richardson, TX, U.S.; www.alibre.com). “But there is a huge potential market segment not yet being served. A major barrier to growth is the high cost per 3-D CAD seat. A lot of companies aren’t willing to spend what might be $5000 to $7000.”

To break down the barrier, Alibre markets a low-cost suite of 3-D software. And, rather than offering it only through limited distribution, the company allows the software to be downloaded from the Internet. “Our software focuses on features people use every day,” says Milliken. “We say we provide 80% of the functionality at 20% of the cost. For a large proportion of the market, our software meets 100% of their needs. We are not going to focus on the top part of the pyramid, but on mainstream mechanical design.”

The company’s Design Xpress is a free 3-D version. It has been downloaded some half-million times, with a current rate of about 10,000 downloads a month. According to Milliken, the software is quite a rich product, permitting functions like printing and data import and export. Where it is mainly limited is in the number of parts allowed in an assembly.

Another way the company aims to increase the 3-D CAD market is with personal 3-D CAD. “When CAD first came out, it was put on mainframe computers and was strictly controlled. Seats were expensive and access was limited,” recalls Milliken. “Today, personal computers have taken over the work environment, much as we think 3-D CAD will take over. We encourage engineers to obtain their own copies of our 3-D CAD, even the free version. We’ve seen many cases where engineers have used their own 3-D CAD on company projects that would normally be done on company 2-D software. Often the company has then upgraded to 3-D CAD. We see a model in which engineers own their own software, much like carpenters owning their own tools.”

Smarter RP

Black & Decker (Towson, MD, U.S.; www.blackanddecker.com) makes use of a Z Corp. Z510 color printer in its industrial design prototype shop. The printer outputs Black & Decker and DeWalt power tool appearance models for the industrial design department. “We’ve had the printer for less than a year,” notes John Reed, master prototype specialist. “We previously used a Z310 model, which had a smaller build capacity and printed in monochrome. The color capability of the new printer saves a lot of time, and produces very realistic models. This is especially important since we are using more colors and more fine color details in our Black & Decker designs. Previously we needed to mask and paint color schemes. Now we are able to produce a fully colored model in less time. It’s also helpful in making a realistic-looking model for our DeWalt line, which has less color differentiation.”

Reed points out that the equipment saves considerable time compared with CNC milling. “Once the data are created, we can machine a model from a block of material on a milling machine. But we then need to mask and hand-paint afterwards. Overall, the process can take about 40 man-hours. Producing a full-color model on the Z510 is usually a matter of less than 8 man-hours.”FONT>

“We help our customers use CAD and RP to compete against companies anywhere in the world,” observes William Cesaroni, president of Cesaroni Design (Glenview, IL, U.S., www.cesaroni.com). The company’s core business is taking a product from concept to a functional prototype. “In countries with less-expensive labor, competitors can put a multitude of people on a project. In order to succeed, we need to be smarter, faster, and more efficient. Not only is RP fast, but it lowers the risk. It can be a window to the future that can protect your company from mistakes resulting in higher tooling costs.

“Rapid prototyping has radically changed since it was first introduced,” he adds. “In the early days, stereolithography (SL) parts were brittle and less durable than production materials like ABS. The equipment was too expensive for most manufacturers to have in-house, but was found mostly in job shops.

“Today, SL parts are much more durable. Engineers can also choose from several other technologies, each with its own advantages. For instance, fused-deposition modeling (FDM) makes parts out of real production materials like ABS. At the same time, smaller, more affordable RP equipment has enabled in-house use by manufacturers. With its own RP equipment, a company can produce a part on the spur of the moment. Until you hold a part in your hand, it’s hard to visualize everything you need to know about it.”

Some prototype suppliers make use of a variety of technologies to bring products to market in short time frames. One example is Rapid Product Development Group Inc. (RPDG; San Diego, CA, U.S.; www.rpdg.com). “Rapid prototyping technologies have improved in terms of part accuracy, surface finish, and material durability,” notes Tony Moran, CEO. “The ‘old school’ technologies (CNC, stamping, tooling, etc.) have improved mainly in terms of speed.”

For instance, Rapid Tooling from the supplier is ready in as little as a week for simple parts, to about six weeks for a large, complex tool with slides/lifters. “Our Rapid Tooling is made via traditional CNC machining and EDM,” says Moran. “But we take advantage of advanced CAD tools, high-speed machining, proprietary mold bases, and around-the-clock teams.”

Low-Volume Production

Cast prototype urethane parts have been around for a number of years, but material upgrades have improved capabilities. In casting, the first step is typically to produce a part via a machining process or with an additive rapid-prototyping process like stereolithography. The part is placed in a box and liquid silicone RTV is added. The solidified RTV is taken from the box and cut, and the part removed. The RTV acts as a master mold to produce another part or parts using thermoplastic polyurethane.

“When I started in this business 10 years ago, parts could be held and placed into position in a product, but they weren’t functional,” recalls Bill Molitor, technical sales representative with Innovative Polymers Inc. (St. Johns, MI, U.S.; www.innovative-polymers.com). “Today’s thermoset polyurethanes are functional about 90% of the time. Our chemists have succeeded in making materials that are closer in physical properties to the plastics they are trying to replicate. We either look at our customers’ materials and try to emulate them, or work to obtain the properties our customers want.”

With this improved functionality, Molitor is seeing more use of this process for limited production runs. “In one case, a company needed a housing for a medical MRI (magnetic resonance imaging) coil. But it produced only 300 a year. Instead of going to the expense of getting tooling and making injection-molded parts, the parts are made by RTV molding. This saves hundreds of thousands of dollars in tooling costs.”

Another molded-urethane part use is for bridge runs until full injection molding production begins, says Molitor. “While this molding process might produce only a fraction of the parts per day that an injection molding machine would make, parts can be made weeks before tooling is available. This can significantly drive down the time to market.”

More companies have started using RP parts for end-use applications, says Tim Thellin, product manager at Red Eye RPM (Minneapolis, MN, U.S.; www.redeyerpm.com), a Stratasys business unit. Stratasys is a supplier of fused-deposition modeling (FDM) RP equipment, which can produce parts made of production thermoplastics. Red Eye has the capacity to run low-volume production orders, typically in lots of 500 to 5000, depending on the type of part (size and geometry). This approach is called direct digital manufacturing (DDM) or rapid manufacturing.

“We find that many start-up organizations are using us to ramp up their production before they transition to tooling,” observes Thellin. “Medical devices, business machines, automotive, and many other industries have used this technology for limited production. In fact, even Stratasys started using its own machines to build parts for its new MC series.”

One-Day Response

A new high-performance stereolithography material was strong enough to permit Vita-Mix Corp. (Olmsted Falls, OH, U.S.) to test its prototype blender jar. The material, RenShape SL photopolymer from Huntsman Advanced Polymers (Los Angeles, CA, U.S.), is clear, allowing engineers to see how the model blended, while the clear look mimicked the final jar appearance. In the past, the company had used SL parts for appearance only. The company also used the new material in its blender base prototypes and found the clarity useful during testing. Prototypes were built by The Technology House (Solon, OH, U.S.).

“Customers can choose from over 100 different stocked resins (or they can provide their own), pick the desired turnaround time, and see the price change interactively. Once customers are ready, our sales staff works with them to finalize the order. At that point, our compute-cluster based software algorithms complete the design of the mold and generate the toolpaths that will be used to machine the mold components. The mold is then assembled, mounted on a standard injection molding press, and the molded parts are shipped to the customer. And all of this can happen in as little as one business day.”

Cytori Therapeutics (San Diego, CA, U.S.; www.cytoritx.com) made use of Protomold’s rapid injection molding. In Cytori’s Celution System, clinicians are able to double the number of stem cells in a volume of adipose tissue (fat). This allows doctors to successfully use that tissue to fill the void left after a breast resection, restoring contour and volume and potentially reversing damage due to radiation therapy.

The system consists of a reusable drive mechanism and single-use therapeutic sets. One of the key challenges in designing the system was development of the largely plastic therapeutic set. “We needed to produce a cage-like component that would be lined with mesh to capture tissue,” says development engineer Bobby Byrnes. Cytori identified First Cut Prototype as a solution. “We were expecting to find the usual additive prototyping processes like stereolithography, and were a little surprised to find a prototyping option that would give us real injection-molded parts quickly and at an affordable price.”

Byrnes and his group determined early in the process that they would use polycarbonate for the system’s disposable plastic components. Based on the expected sterilization process and operation of the system, they wanted a material that was strong, that had high heat and chemical resistance, and that wouldn’t leach out plasticizers as some resins do. They needed to develop a prototype and then roll smoothly into production for product verification and validation (V&V).

The overall goal of the V&V process is to make sure that the device is safe and effective. “We test a lot of different aspects of the device,” says Byrnes. “Besides withstanding the sterilization process and making sure that it can handle heat, cold, and humidity, we have to make sure it’s biocompatible, that it performs the way it should in operation, and that it can stand up to the rigors of international shipping even after sitting on a warehouse shelf for an extended period of time. Then there are the separate approval processes for regulatory bodies in the United States, Europe, and Japan, all of which require validated parts. You can see why it’s important to have both real parts that perform up to production standards and approved vendors that meet our rigorous quality standards.

“Working with Protomold, we submitted our CAD design to the ProtoQuote online quoting system. Basically, our design worked, but we’re not mold engineers so the design modifications ProtoQuote requested for better moldability were a big help. After making the changes, we requested and got three-day turnaround on the prototypes. To date, we’ve had five different components of our disposable set made by Proto­mold. These parts have worked so well that we were able to go right into production for the clinical trials. It’s been a big help in moving our development and approval process forward.”

Testing SL Parts

DSM Somos (Elgin, IL, U.S.; www.dsm.com) a division of DSM Desotech, reports it issued five new stereolithography (SL) materials last year and two more this year. Included is a new ultraclear material for lenses or see-through parts such as refrigerator drawers. The company has developed a chemistry platform for its stereolithography materials, with a related manufacturing facility investment. Parts made from the new materials have both high stiffness and high impact properties, a combination that the company says was previously unavailable. With the new materials, the company sees more of a market for limited-production stereolithography parts. It is working to obtain long-term stability data so design engineers can specify them with confidence in more applications.

As an indication of how SL materials have changed, a mower manufacturer looking to produce a discharge chute came to The Technology House (Solon, OH, U.S.; www.tth.com).

For a durable part such as this, a typical rapid-prototyping approach is to use a cast urethane. But this process involves multiple steps, including building a master pattern, creating an RTV silicone mold, and mixing and pouring cast urethane. Instead, Technology House suggested producing the part directly on an SL machine using DSM Somos’ new DMX-SL 100 material. This resin has a notched Izod impact resistance of 70 J/m, similar to laser sintered materials.

Built on an SLA 7000 from 3-D Systems Corp, (Rock Hill, SC, U.S.; www.3-dsystems.com), the discharge chute was created in two pieces and glued together. It was used on a mower that was operated for two days on a grass field and survived, providing the design feedback needed by the customer.

For stereolithography parts that need to be especially durable, DSM Somos suggests they be metal plated. “Plating can make a part several times stronger,” points out Jim Reitz, business manager. “Plating can also be done selectively inside a part to provide EMI shielding.

“Metal plating of prototypes has been done on a limited basis for about four years. Now we market the MC2 (metal clad composite) plated-parts concept through service bureaus, which we certify. An engineer can simply call the bureau and request a type of metal-clad structural construction. They don’t need to know all the technical details, but will just specify what the part should do. The service bureaus, in conjunction with metal platers, can quickly have low-volume parts to the customer, at half the cost of producing machined parts.”

Emulating Paper Printing

Z Corp.’s 3-D printers build physical models by depositing a binder solution through an ink-jet printhead onto layers of an engineered plaster-composite powder. Unused powder is recycled. With this method, a part can be printed in full color at the rate of 25–50 mm (1 to 2 in.) vertical per hour. This is reportedly five times faster than competing models. In addition, multiple parts can be printed simultaneously, resulting in increased throughput. Prototype parts can be turned around in hours.

Roger Kelesoglu, director of supplies, service, and support at Z Corp. (Burlington, MA, U.S.; www.zcorp.com) sees companies using the technology much like they use paper printers. “Because our 3-D printing is fast and inexpensive, it makes sense for the end-users to have the technology in-house, much as they do with paper printers. Some engineers will print several prototypes before even showing one to another engineer. Of course, with paper copies there are times, such as when you have a lot of copies to make, when it makes sense to go to Kinko’s. Similarly, end-users can sometimes take their 3-D printing to a service bureau.”

Continuing the paper-printer analogy, 3-D printers can operate in a draft mode, for fastest operation. Different powders or binders can be used, depending on the desired part properties. Parts, which are porous when printed, are dipped in a resin upon completion for additional strength. The user can choose the appropriate resin to optimize certain properties.

Creativity Still Needed

Using today’s advanced software to achieve digital prototyping, manufacturers can better conceptualize, model, and test designs before they are ever built, observes Gregg Montgomery of Montgomery Design International (Westmont, IL, U.S.; www.montgomerydesign.com) “Using full integrated tools to develop a digital model brings together design data from all phases of the development process into a single digital prototype. Designers and engineers can then use this model to better visualize and optimize concepts that appeal to consumer tastes and reflect their brand image.”

But he adds that technology isn’t everything. “One potential downside to this improved way of working is that anyone who is capable of producing a digital model can produce a photorealistic product image. Some believe this might supplant the need for a qualified designer. This reflects a misunderstanding of the designer’s complete role in the process, and overstates the ability of the software. CAID (computer-aided industrial design), CAD, rapid prototyping, and CAM are simply the new tools of the design process. They save time and effort, and ensure accuracy, but they have yet to replace the creativity that still resides with the human mind.” 



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