Additive Techniques Come to Low-Volume Manufacturing

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December 14, 2011

Additive manufacturing (AM) techniques produce low volumes of complex products with high quality and precision. These products typically include medical and dental prosthetics and implants. With engineering-quality materials, aerospace and automotive components can also be fabricated.

As a form of AM, 3D printing techniques have long been used for rapid prototyping. Some of these low-cost printers help speed the design process. Low-volume AM differs from 3D model and prototype printing in how parts are used and the number of parts produced. Volumes tend to be in the tens, hundreds, or even low thousands. Techniques include laser sintering (LS) and fused deposition modeling (FDM). Materials are generally thermoplastics, but some metals are sintered.

"Unlike models and prototypes, end-use production parts often must endure extreme temperatures, humidity, direct sunlight, and sometime abusive handling," Terry Wohlers, principal consultant and president of Wohlers Associates, told us in an interview. "They must hold up over a period of years, maybe even decades, such as in aerospace."

Standard subtractive manufacturing techniques and injection molding don't always make sense in some industries and applications. The high cost of injection molding tools must be amortized over several thousand units. AM can be competitive when producing only 2,000 units, and injection molds cost a lot, making the unit cost for tooling alone very high, says Bryan Crutchfield, managing director for Materialise USA. "With AM, you also have the flexibility to make a design change in CAD data, so you don't have to also change the hard tooling, and you can build on demand."

Injection molding processes run a huge batch at once, necessitating stockpiles of material, but AM saves on material obsolescence costs. Crutchfield says the process needs several hours to build up a part layer by layer, versus three to 40 seconds of cycle time per part in high-volume manufacturing. "But if you take into account all the costs -- including tooling, materials, and investment for shorter runs -- that's when you can favorably compare AM to traditional manufacturing. Stamping dies and injection molds are very expensive to produce up front and much more difficult to change."

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