This technical information has been contributed by
Prototypes Plus Inc.

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Rapid Prototyping Firm Gears up for Aerospace Growth

Rapid Prototyping

Laser sintering is key to the company's plans for serving high-tech markets.

Complex, precision parts that integrate multiple functions in a single design are high on the list of needs of aerospace manufacturers. Prototypes Plus Inc., a full-service rapid prototyping company based in Menlo Park, California, is looking to expand its role in helping aerospace OEMs meet this need, as well as others, with a laser sintering process that doesn't require tooling or assembly. The ISO 9001:2000-certified company recently announced the launch of a new production facility--nearing completion at an undisclosed location--that will focus on laser sintering and digital manufacturing for the aerospace and other high-tech industries.

Prototypes Plus maintains a 12,500-square-foot headquarters facility in Menlo Park, where it offers stereolithography (SLA) and RTV tooling and casting, in addition to laser sintering. To meet growing demands for functional prototypes and short-run production, the company offers precision CNC machining, as well as secondary CNC milling and turning. Prototypes Plus also offers finishing services that include custom masking and painting, color matching, EMI shielding, custom graphics, pad printing and silk screening, and plating and polishing.

Design-2-Part Magazine's David Gaines spoke with Prototypes Plus President George Dukes recently about the company's value proposition, the advantages and limitations of laser sintering, and the recent emergence of laser sintering as a viable, low-volume digital manufacturing process.

Q: What are the benefits of laser sintering?

A: In the past, in order to get some of the plastic properties you wanted, you would use stereolithography (SLA), and make an RTV tool, and then cast a urethane material. If you can skip those processes and go to laser sintering (LS), you're not only saving time, but you're saving RTV tooling costs and the labor of doing an RTV casting. There's very little labor in producing an LS part, and any geometry can now be laser sintered. It's very applicable to the aerospace industry, where the volumes are low, but they need very precision parts with complex geometry. There are several parts for fighter jets -- like the F-18, F-22, and F-35 -- that are being designed specifically with laser sintering in mind.

Q: Can you describe how your manufacturing technology is used?

A: We handle short-run production for high-end consumer, military, and aerospace parts that are for R & D or special operations. We also offer stereolithography (SLA). We have the largest SLA machine in the U.S., the Sony 9000D. We still offer the SLA process and RTV urethane castings for some applications. We sometimes use SLA for beta units for the medical industry, and urethane cast parts for aviation applications, [using] basically a low-pressure liquid injection molding process. Instead of using steel tooling, we use silicone molds made with our laser sintering technology. Sometimes we pull them off of SLA master patterns, or CNC machining master patterns. We use this technology to make beta units and prototypes. We make things like dental carts, medical carts, enclosures for blood monitoring systems, and DNA testing equipment.

Q: How does the urethane casting process compare with laser sintering?

A: The urethane castings are produced with a higher level of cosmetic finish. They can be molded in color with specific textures, and for the most part, they resemble an injection molded part. We may have machined some of the components in a multi-component assembly, maybe out of polycarbonate, Delrin®, or even nylon that may have been produced in a urethane casting. With laser sintering, we can produce these parts a lot cheaper and get similar properties. They can be built with more combined parts, creating a more complete mechanical device, and maintain a structural aspect.

Q: Can you tell us about the parts you manufacture for aircraft and automobiles?

A: There are components that we do for unmanned aircraft that are fairly complex and [the customer] might only want three or four parts. These three or four parts might be integrated into a single component that can be digitally manufactured using laser sintering. It's a very durable material and has a reasonably nice smooth finish. The end uses for these parts can be very sophisticated and high-end, and have been certified by the aerospace industry and, in some cases, the automotive industry.

A lot of very high-end custom vehicles, or test vehicles (such as a Corvette or a Chrysler project),  will utilize the laser sintering process because of the heat deflection temperatures and high tensile strength relative to the more traditional SLA process. They will use the LS process over an SLA part, since the nylon parts are much stronger, and the LS parts can be plated, painted, and printed on as well. In the past, you would have to use aluminum or mild steel tooling that had to be machined so that you could make a headlight assembly that would withstand the environments that these cars would be put through. The machining of complex tools can now be eliminated with LS.

We skip the whole tooling process when we use laser sintering. To us, laser sintering is digital manufacturing because of the material properties. Some people claim that SLA has properties that can be used as an end product, but I'm not of fan of that. But I think those properties are prevalent with the nylon LS parts.

The aerospace industry and Daimler-Chrysler have signed off on the LS process because it is precise enough for their sophisticated parts. With the SLA process, you have limited structural integrity. There are concerns about heat and warping, and the parts don't take impact very well. LS is being adopted for these concept cars and test cars because it can withstand higher heat and limited impact testing, and it has many of the same properties of an injection molded part.

Q: Are there any limitations to laser sintering?

A: I think right now the only limitations to laser sintering are the available materials that are primarily nylon-based. But there are fire-retardant nylon materials available, and nylon materials that we can add glass and aluminum to. There are also materials in the works that will allow the automotive racing industry to start adopting this process. I think that new materials will eventually come online outside of the nylon chemical makeup, and then the industry will take another jump into even more diverse end products. As materials get better and more and more of these machines are in the manufacturing stream, prices will start to come down. And you'll eventually see simple parts, like wiring harnesses, gauge enclosures, louvers, and air ducting, becoming more complex and integrated into mainstream manufacturing.  
 

Q: Are OEMs becoming more aware of the advantages of using laser sintering?

A: There is no doubt that laser sintering is a growing industry, even though there are still very few digital manufacturing facilities that can meet the stringent specifications of the aerospace or automotive industry. We are one of only about three in the U.S. that have these capabilities. Over the past five or six years, the technology and materials have gotten better for laser sintering, which is allowing it to now move into the realm of low-production digital manufacturing. It is no longer considered just a prototyping process, but a viable manufacturing process by several large aerospace companies, one being the Boeing Corporation.

Q: What unique applications are becoming prevalent with laser sintering?

A: The parts can even have articulating points built in. Say, for example, you want to incorporate a hinge onto an air duct. In the past, you had to use a separate hinge and attach it to the air duct. Nowadays, they are designing the hinge and the air duct as one piece for laser sintering. This is similar to what's happening to the louvers on an air duct. Typically, the louvers are two or three individual components and someone then has to assemble them onto the duct. With laser sintering, the individual louvers can be made as one piece. So these are the articulating points that are now built into the parts.

Q: How would you sum up the major advantages of using laser sintering versus other processes?

A: There are a number of inherent advantages to the laser sintering technology, none greater than the elimination of hard tooling. Having the ability to go directly from 3D CAD to a completed prototype or production part literally overnight allows engineers to be very aggressive in their part design. If redesign is required, it can be accomplished with electronic changes to the 3D file, and [the part can be] built again that same day without the concern of having to use obsolete hard tooling, falling behind in schedule, and exceeding budget requirements.

If continuous improvement is a stated goal, then the need to roll part revisions and change designs goes hand in hand. Presently, all industries must look at this in two ways: part improvement and cost impact. Decisions are made in most cases on cost impact, because of the cost of building new tooling and, subsequently, storing the original tooling for years to come to produce the original part. In LS technology, no hard tooling is necessary, and the subsequent part revisions can be rolled to incorporate the latest changes. Original designs are stored in electronic format that can be rebuilt as required. LS technology is the ultimate in "Just in Time" manufacturing.

Q: How is the laser sintering process able to produce parts with virtually any complex geometry?

A: Laser sintered parts are built in very thin layers--generally, 0.004 inch to 0.006 inch (0.1mm to 0.15mm)--and only that portion of the part in the 3D model is built. The powder surrounding the laser sintered part remains a powder while the part area is liquefied and then begins hardening in the desired shape. Additional powder is deposited in the part bed and the process repeats itself until the entire part has been built. The remaining powder within the build chamber holds the sintered part (self-supporting) together until it has hardened to the point that it can be handled without harm. At that point, the powder is removed, leaving the completed part.

The complex geometries are available because the powder is easily removed from areas that normally would be formed by hard tooling and, in very complex shapes, there would be no way to remove the tooling from the finished part. We are now able to build exactly what the designer has conceived without the restraints of conventional manufacturing techniques.

Q: What other high-tech industries, in addition to aerospace, do you anticipate that your new facility will serve?

A: The medical industry is the other area we are looking to serve. With the facility being AS9100B compliant, it is a short step to comply with FDA requirements. We are looking at implantable devices, as well as surgical instruments. The laser sintering technology is a natural for this industry not only because of its ability to build uniquely shaped parts for limited applications, but because many of the materials used already hold a USP Level VI certification. Traditional tooling is not an option because of both the cost and long lead times, but in our case, we can build multiple iterations in a short time as required for any particular procedure. Medical and aerospace components are cutting-edge technologies, and we feel laser sintering is, as well, which is why we are establishing an independent digital manufacturing facility to produce parts at the highest level possible.

For more on Prototypes Plus, visit www.prototypesplus.com

SLA is a registered trademark of 3D Systems, Inc.

Delrin is a registered trademark of DuPont.

This technical information has been contributed by
Prototypes Plus Inc.

Click here to find suppliers

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