Rapid Manufacturing

Using additive fabrication to make customized parts and limited production runs without tooling is fast becoming the single most important application for the technology. Much more detailed information is provided in the Rapid Manufacturing section concerning the methods and long-term potential. The Rapid Tooling & Metal Parts section covers numerous processes for making parts out of metals. While there's obviously a lot more ground to cover, it's still possible to provide some rules of thumb as a starting point.

Plastic Parts

Selective laser sintering (SLS) is frequently used today to directly manufacture both plastic and metal parts for high-value-added applications. It's the method that comes closest to the intrinsic properties of engineering plastics.

However, fused deposition modeling (FDM) is rapidly increasing its market share for these high-value parts, and in addition is addressing many more mundane applications, as well. This is true for several reasons, not the least of which is that more than 2,000 FDM machines are now being sold each year. Quite simply, this has led to a huge increase in the number of locations where rapid manufacturing using them can be done. The relatively low cost of the systems and their ability to economically build a few, or even just one small part at a time are two added important reasons. To be economical, expensive technologies that use a build chamber full of material have to be kept busy by populating that volume with numerous parts during a single build cycle. In contrast, there's no big pot of material used in FDM, and lower costs permit less efficient use. An additional reason is provided by the properties and choice of materials used in the FDM process. The use of robust, durable ABS and other true thermoplastics provide predictable and stable results.

Stereolithography and related photopolymer-based processes are also used as a manufacturing method for some applications. They have the advantage of better accuracy and finishes, but on the negative side the materials only emulate engineering thermoplastic properties and some of them are unstable over time. Also, most of the systems are expensive which means that they are best for high-value-added applications. Improving material choices and properties will likely increase the number of rapid manufacturing applications for the technology, but it's an uphill battle to gain ground against other technologies. Stereolithography is most often used to manufacture small parts such as hearing aid shells at the present time.

Metal Parts

[SLM]

While a large fraction of applications for additively-fabricated plastic parts may be covered with today's material choices - limited though they may be - the same can't be said for metal parts. As one example, a polypropylene dust cover will still function adequately if made from another plastic such as ABS. In contrast, metal parts are nearly always highly-functional, and the required properties are generally not as easily substituted. An adequate substitute metal might also be prohibitively more expensive.

Metal material choices available with additive technologies today are mostly the result of system vendors addressing specific applications for their equipment. As a result, it's easiest to select a technology for a metal rapid manufacturing application by examining the list of materials available for each method. If you need titanium for an aerospace or medical application, that will immediately eliminate some technologies and equipment vendors. If you need gold, you can eliminate all but one vendor. Be aware that at this stage of technology development it may simply not be possible to accomplish your intended application. There are a lot of choices, but there are plenty of things missing from the engineer's customary armamentarium.

The most popular method of additively fabricating metal parts is selective laser sintering (SLS). It offers a reasonable selection of materials and it's widely available. Processes which are similar, such as selective laser melting (SLM) and electron beam melting (EBM) offer the advantage of fully-dense parts and an equally-wide, if not wider, material selection. The choice among all these methods can largely be based on availability, cost and materials because of their high degree of similarity.

Laser Engineered Net Shaping™ (LENS ) and other laser powder forming technologies are being used to fabricate parts for aerospace applications and injection molds. The technologies lend themselves to making very large parts and they can also be used to repair parts or molds. The resulting parts may even have better properties than those made from intrinsic materials.

Impellers for an aerospace application directly fabricated by selective laser sintering (SLS).	Titanium engine valves fabricated by LENS ® technology.
(Courtesy, On-demand Manufacturing.)	(Courtesy, Optomec.)

Three dimensional printing (3DP) has been used to make ceramic gas and liquid filters, structured medications and medical implants. It's also being further developed to make ceramic and metal parts.

Solidica has developed a lamination object manufacturing (LOM) method called Ultrasonic Consolidation™ that is based on CNC cutting of thin, metal strip material. The strips are subsequently bonded together ultrasonically to form the final part. The process can be used as a manufacturing method to make composite materials, or to imbed fiber optics in metals for smart structures and communications applications.

MicroTEC GmbH (Germany) offers two proprietary stereolithography-like processes appropriate for manufacturing very small objects and systems. The company says these photopolymer-based methods are capable of batch fabrication rates to hundreds of thousands of parts per hour.

FUJIFILM Dimatix, Inc. makes inkjet-based systems that can be used for diverse additive manufacturing applications at the micro- and meso-scale.

Microfabrica Inc. offers the electrochemical fabrication process (EFAB) which can produce very small metal parts and complex assemblies in large volumes. The materials offered at present are nickel-cobalt and rhodium alloys, but the technology can potentially accommodate any material that can be plated. The process was introduced commercially in 2002 and it was developed at the University of Southern California.

CAM-LEM offers a process similar to laminated object manufacturing (LOM) that can fabricate complex ceramic parts.

Numerous additional technologies are being developed covering a wide range of applications. Some are for specialized fields such as nanotech, microfluidics and electronics, but they have more general applications, as well. Much of this work is described in the Rapid Manufacturing section.

A tiny micro-gripper, including magnetic components, fabricated by microTEC out of photopolymer.	An inductor assembly fabricated using EFAB.	A metallic, multilayer toroid fabricated using EFAB.
(Courtesy, microTEC GmbH, Germany)	(Courtesy, Microfabrica Inc.)	(Courtesy, Microfabrica Inc.)