Introduction
Many of the world’s agricultural and construction companies depend on the heavy-duty agricultural and construction equipment manufactured by CNH America LLC of Lake Forest, Illinois, USA. Every part, regardless of size, must be precisely made to ensure the reliability and durability of the machinery as well as operator safety. At CNH, that high level of precision begins with cast metal prototypes and low-volume production parts produced from sand casting patterns made on its SLS® system in DuraForm™ material, purchased in 1998 from 3D Systems. The Rapid Prototyping Department is located in one of CNH’s main engineering sites at New Holland, Pennsylvania, USA.

The Challenge
CNH needed to find an efficient and cost-effective alternative to outsourcing its prototype sand casting pattern-making work to service bureaus, none of which were using selective laser sintering (SLS™) technology. CNH was often disappointed in the results--patterns and parts that were dimensionally unstable and susceptible to moisture. Casting patterns get pushed in and out of sand numerous times, so they must be resistant to the chemicals in the sand and to the moisture that can cause the patterns to swell or change shape. Since CNH typically needs 20 to 50 of each cast metal prototype part to complete testing for function and durability, the time spent sending defective parts back for re-casting slowed down product development and production. In addition, the service bureaus’ priorities often caused CNH to "wait in line" for its parts, sometimes behind its competitors. These quality and time-to-market issues compelled CNH management to consider acquiring an in-house solution for rapid prototyping.

"Our main goal was to find a system that would help us streamline the creation of sand casting patterns," says Luke Nolt, casting specialist at CNH. "We also wanted a system that we could use for a variety of other applications. That led us to the SLS system and DuraForm material from 3D Systems."

The Results
Using the SLS system, CNH cut the time it took to make casting patterns by 50 percent, and even more in some cases. Instead of spending three or four weeks, engineers can complete the process in just a few days. Nolt says that having the DuraForm material prototypes and patterns also makes working with the foundries more efficient during the prototype casting phase.

"Developing the perfect casting process for a part now begins immediately with the prototype," Nolt says. "When we say we need 5,000 parts, the foundry already knows the requirements for the casting process because they’ve previously made the prototypes. They can often use the same process with no changes. It’s a distinct advantage." With low annual requirements and design changes minimized, there is also a push to use the prototype Duraform pattern as a production tool. To date, CNH has put numerous patterns into production making more than 1,000 castings each annually, with some patterns in service over four years showing no appreciable wear.

Based on the benefits of creating sand casting patterns with DuraForm material, CNH began to expand the use of the SLS system to make investment casting patterns with CastForm™ material. "Investment casting has allowed us to cast steel parts quickly, which opened up a whole new world of simulated forged parts," Nolt says.

Indeed, the SLS system has opened up a new world of broader functionality over the years as CNH continues to discover new ways to use it. According to Peter Haldeman, rapid prototype engineer at CNH, the SLS system has run 24 hours a day/7 days a week since its installation in 1998 and is used for everything from parts prototyping to low-volume manufacturing. The system has given CNH the capabilities to simulate forgings as well as injection, RIM, Roto, and blow-molded parts. Also, creating marketing displays, and providing communication tools for suppliers have been functions beyond CNH’s initial concept of using the system for making casting patterns.

Haldeman explains that he operates the system to make a diverse assortment of prototype parts. These components range from very large agricultural equipment parts such as shielding, which he has to segment and then re-assemble once the components are made in the SLS system, to the smallest parts. He notes that creating prototype parts in the SLS system enables CNH to respond quickly to the need for test runs on specific parts without first investing in tooling. Haldeman recently made a coolant over flow bottle for engine systems that can be coated and waterproofed so that functional testing can be performed.

"One of the big benefits of having the SLS system is that we can build parts in it with such exceptional durability and integrity that we can run coolant through them and demonstrate on the factory floor or the field how the parts and systems actually function when assembled," Haldeman says. "It’s very impressive, and it helps us get testing done in rapid time."

Haldeman says that using the SLS system has also shortened lead times and reduced time-to-market for CNH. "We’ve cut our lead time at least in half for cast metal parts," Haldeman says. "Also, by confirming the integrity of the part design early in the process, we have been able to reduce time-to-market by ensuring that any type of parts our engineers start with are right and won’t have to be sent back for re-tooling."

Haldeman notes that the SLS system also enables CNH to respond more quickly to design changes and customer requests. "We were testing a casting part and saw that it needed a mirror image added to make the system function correctly," Haldeman says. "Because we had rapid prototyping capability with the SLS system, we could make the new component quickly and incorporate it into the product. We saved an entire testing year, and we were able to get the product out on time."

Another important benefit of the SLS system is the ability to do cost-effective low-volume manufacturing of replacement parts for equipment that has been in the field for many years. "Being able to supply service parts for older equipment is a big factor in providing a high level of customer service," Haldeman says. "Plus, not having to create the tooling for these low-volume runs is a huge benefit. It could cost anywhere from $2,000 to $5,000 to re-tool a run of 10 pieces, but by making the parts in the SLS system we don’t have to make that investment. Also, it’s difficult to find suppliers that will even consider running such a small volume, so the benefits go beyond money. It’s all about time savings, practicality, and customer service."

The SLS system delivers the following benefits to CNH

• Eliminates long lead times for casting patterns and prototypes, resulting in faster time-to-market
• Reduces time to make sand casting patterns by 50 percent or more
• Enhances customer service by enabling low-volume manufacturing of parts
• Improves efficiency and communication with foundries and suppliers
• Enables the live demonstration of the durability and integrity of parts for faster testing