RP Past and
Rapid prototyping are words used to describe a particular phase of fast product development. Usually, it refers to the modeling, simulation or physical prototyping of a new design early in the design cycle. Over the past few years, industry groups, the media and others have labeled RP to mean rapid prototyping of mechanical components. Examples are plastic injection molded parts and metal castings that go into everything from copy machines, computers and cellular phones to automobile dashboards, aircraft subassemblies and medical diagnostic equipment.
Developers of software interfaces and printed circuit boards also use RP technologies and strategies. Their tools are different from those used for mechanical design, but their purpose is to speed the design process and enhance communication. The information presented here focuses on RP for mechanical design, although most of the benefits apply to other types of RP.
RPís increase in popularity
RP for mechanical component design began to expand significantly in 1994, and it continues to grow. The reason for this growth, first and foremost, is that manufacturing companies are becoming familiar with what the technology has to offer, an educational process that has taken years. Second, the range of RP processes that is commercially available has improved. Today, it is possible to produce relatively accurate parts in materials such as epoxy resins, ABS plastic and glass-filled nylon.
Third, companies are finding that they can justify the cost of RP on the basis of improving design quality and avoiding expensive mistakes. Receiving a physical model of a proposed design early in the design cycle permits them to make improvements when changes are inexpensive, thereby helping them to catch design errors long before production tooling. Oversights at this phase can cost tens, even hundreds of thousands of dollars, and can delay product shipment, giving the competition an advantage. A decade ago, firms could get away with delays of weeks or months, but this is no longer an option, especially with products that have a life of only a year or two.
Advances in CAD solid modeling have contributed to the growth of RP. Without a CAD model, it is impossible to produce an RP part, with the exception of data from CT and MRI scanners and 3D digitizing systems. Note that they represent a small percentage of the data driving RP machines. So when referring to RP as an aid for mechanical design, almost all parts are built from a CAD model, and nearly all of them are solid models. For this reason, the growth of the RP market is tied to the growth of CAD solid modeling.
RP and CAD solid modeling are complimentary technologies, so they help to justify one another. Many companies have purchased solid modeling systems, but not until they made the decision to integrate RP. Companies are also buying solid modeling systems because it secures them a future path to RP. So they really do help sell one another. Some companies view the solid model as the soft (virtual) prototype and the RP part as the hard (physical) prototype.
Systems for mechanical design
RP systems for mechanical part design started in 1988 with Stereolithography (SLA) from 3D Systems, a process that solidifies layers of UV-sensitive liquid polymer using a laser. In 1991 came Laminated Object Manufacturing (LOM) from Helisys, Fused Deposition Modeling (FDM) from Stratasys, and Solid Ground Curing (SGC) from Cubital. LOM bonds and cuts sheet material using a computer-guided laser. FDM extrudes thermoplastic materials in filament form to produce parts layer by layer. Also working with UV-sensitive liquid polymer, SGC solidifies whole layers at once by illuminating a flood of UV light through masks created with electrostatic toner on a glass plate.
Selective Laser Sintering (SLS) from DTM became available in 1992, followed by Direct Shell Production Casting (DSPC) from Soligen in 1993. Using heat from a laser, SLS fuses together materials in powder form. Using an inkjet mechanism, DSPC deposits liquid binder onto ceramic powder to form shells for use in the investment casting process. MIT invented and patented the process and licensed it to Soligen. Model Maker (MM) from Sanders Prototype became available in 1994, and Ballistic Particle Manufacturing (BPM) from BPM Technology in 1995. Both MM and BPM deposit wax materials using an inkjet print head.
Other technologies and companies have come and gone over the years. Quadrax developed the Mark 1000 stereolithography system, introducing it in 1990. Patent litigation led to the absorption of the technology by 3D Systems in 1992. DuPont developed stereolithography technology that it called SOMOS, and licensed it to Teijin Seiki in 1991 for exclusive distribution rights in parts of East Asia. Then, in 1995, DuPont licensed it to AAROFLEX for distribution rights in North America, with an option to acquire distribution rights in other countries. Companies such as Light Sculpting, Sparx AB and Laser 3D have developed and introduced versions of RP, but they have not had a commercial impact on the RP industry.
Paper lamination systems (Kira Corp of Japan and Kinergy of Singapore) and as many as seven stereolithography systems are available from Japanese companies. SLA products from CMET, Denken, D-MEC and Teijin Seiki represent the lionís share of the RP systems sold in Japan. Also available for sale are stereolithography products from German companies EOS and Fockele & Schwarze. EOS also offers a system based on laser sintering that competes with DTM in Europe. Note that none of these foreign machines are available for sale in the USA.
The primary RP market grew by 49 per cent to an impressive US$295.1 million in 1995. This figure includes revenues generated worldwide from product sales and services. The secondary market segment was estimated at US$176.1 million for 1995, bringing the annual total to more than US$471 million. The secondary market includes secondary tooling created from RP patterns, and castings and duplicate parts produced from this tooling.
An estimated 526 RP systems were sold in 1995 by 15 system manufacturers located in the USA, Germany and Japan. 3D Systems, Inc led the market in unit sales again, but the margin is narrowing. As the leading supplier of stereolithography machines, 3D Systems sold 130 units, while fast-growing Stratasys, Inc sold 121 of its FDM systems.
Service bureaus make up a large and vibrant part of the industry. The 1995 service bureau market was estimated at US$135.5 million, representing annual growth of almost 43 per cent. Meanwhile, a new market is beginning to unfold as US system manufacturers roll out less expensive, office-friendly systems targeted at product designers.
New technologies, products and applications have led to a new level of excitement in the RP industry. These developments, coupled with strong growth in product sales and services, present a very optimistic view of the RP industry and its future. Soon, the RP industry will be measured in billions of dollars.