Wohlers Associates, Inc.
This paper was presented in December 1999 at EuroMold in a conference titled "Rapid Tooling's Strategic Benefits & Risks."
Technologies for rapid product development continue to evolve and improve. Applications of rapid prototyping (RP) and freeform fabrication in organizations now span from early concept development to the manufacture of final production parts. The many ways in which the technology is being applied throughout product development, tooling, and manufacturing has fascinated observers worldwide.
The interest in rapid tooling (RT) is fostered by the potential to slash both cost and time in the development of tooling and the production of parts. Companies are recognizing opportunities to apply methods of RT to prototype, bridge, short-run, and production tooling. Under the right circumstances, some methods of RT work well for some parts. Meanwhile, developers are faced with a number of problems associated with dimensional accuracy, flatness, surface finish, mold life, size, and even build speed. Unless they can sufficiently address these problems, RT will encounter difficulty in becoming a mainstream alternative to conventional methods of tooling.
Industry consultant Terry Wohlers is president of Wohlers Associates, Inc., a firm he founded in 1986. The company provides technical, marketing, and strategic consulting on new developments and trends in product development, prototyping, and tooling. Wohlers' highly sought after views and opinions come from years of collecting and analyzing market data, coupled with his work as an advisor to major organizations in the U.S., Europe, Asia, and South America. He has authored more than 230 books, articles, reports, and technical papers on engineering and manufacturing automation. In 1992, Wohlers led a group of 14 individuals from industry and academia to form the first association dedicated to rapid prototyping. Last year, he co-founded the Global Alliance of RP Associations (GARPA) involving 14 member nations around the world. Wohlers is the chairman of the conference titled Rapid Tooling's Strategic Benefits and Risks at Euromold '99.
Some believe that RP is best suited for "3D printing" applications. The idea is to quickly and inexpensively "print" models for design evaluation and validation early in the design cycle when engineering changes are inexpensive. Three companies—3D Systems, Stratasys, and Z Corp.—have developed 3D printing systems.
Others believe that RP must ride the tooling wave—a $65 billion industry according to some industry estimates. The RP industry has unofficially adopted "rapid tooling" as the name used to describe methods in which stereolithography, laser sintering, and other freeform fabrication technologies are used to produce core and cavity mold inserts for plastic injection molding.
Still others believe that RP processes can and will be used for the direct fabrication of production parts that go into end-use products, especially parts that are complex and difficult to manufacture any other way. Many are calling this "rapid manufacturing." Because of the way RP systems build parts layer by layer, it is possible to fabricate almost any geometry of any complexity.
With parts stored as solid models, it becomes almost trivial to produce highly complex structures with 3D printing. Furthermore, companies can produce these models in a day or less instead of weeks. In recent years, RP has had a dramatic effect on reducing the time needed to move the design from the digital and paper phase of development, to prototyping and testing. 3D printing is helping to accelerate this movement. Many companies have reported the development of complete models and prototype parts without a single engineering drawing.
Models from conventional RP systems are often built as the first physical manifestation of a CAD model. After the model has been built, the CAD data changes, and it often changes quickly. The designer discovers something in the physical model that he did not see in the computer version of the model. The RP cycle—as fast as it is—is not as fast as it needs to be to keep pace with a good designer. This lag in time, coupled with the cost of an RP model, discourages designers from building expensive RP models for concept modeling. Due to cost and speed advantages offered by 3D printing, chances are good that it will take over a significant percentage of RP models now being built for design review and visual inspection. Enhancements to 3D printers will further improve the return on investment, making it difficult to justify the higher prices and hassles associated with high-end RP. Could this cause RP systems, as we know them today, to fade into extinction?
The breadth of materials available, coupled with much better part quality, gives high-end RP systems an edge over 3D printers for demanding applications. Presently, 3D-printed parts do not match the strength, accuracy, and surface finish of high-end RP parts. For now, that will help justify the higher prices. Even so, the manufacturers of these systems are being forced like never before to enhance the price/performance ratio. 3D Systems, for instance, replaced its Actua 2100 system with ThermoJet, a system that is three times faster, offers stronger material, and costs about $15,000 less.
Many companies are pursuing the development and commercialization of RT because of its market potential. In 1998, the secondary rapid prototyping (RP) market segment, which includes RP-driven tooling and core and cavity inserts created directly from RP processes, grew 17.5% to an estimated $376.7 million, according to a study conduced by Wohlers Associates. Japan's Ministry for International Trade and Industry (MITI) estimates that tooling worldwide is $39 billion. Meanwhile, Shoichi Kuroda, president of Kuroda Precision Industries in Kawasaki, Japan, estimates that the mold and die industry is $65 billion worldwide.
Two broad categories of rapid tooling (RT) have developed. One category involves indirect approaches that use RP master patterns to produce a mold insert. Examples of indirect methods include aluminum-filled epoxy tooling and 3D Keltool from 3D Systems. The second category is a direct approach, meaning that an RP machine builds the actual core and cavity mold inserts. RapidTool from DTM and Direct Metal Laser Sintering from EOS are examples of direct methods.
Many of the approaches to RT are developing behind the scenes in closed laboratories in the U.S., Europe, Asia, and other parts of the world. Companies are developing RT methods for in-house use with no intention of licensing the technology or making it available commercially. These efforts are directed at the development of an approach that offers a strategic advantage over their competition.
The interest in RT is fostered by the potential to slash both cost and time in the development of tooling and the production of parts. Opportunity abounds for prototype, bridge, short-run, and production tooling. RT also offers a potential benefit that one cannot realize with conventional machined tools. With RT, you can optionally embed conformal cooling lines in the mold. Conformal cooling lines are copper tubing or channels fabricated directly into the mold. These channels conform to the geometry of the mold cavity, thus removing hot spots in the mold and reducing injection-molding cycle times. Research indicates that cycle time reduction using conformal cooling has a significant impact on part cost and production rates.
More than 20 RT developments have been announced to date. Each of them comes with a unique set of strengths and limitations that typically cater to niche applications, although few of them are ready for broad-based, commercial use. Yet, because of their possible impact, these developments are causing a flurry of inquiries from companies in developed regions around the world.
Many manufacturing companies are trying to determine if now is the time to consider one of these new approaches. Some of the methods listed in the previous table are in a developmental phase or on the verge of commercialization. Processes such as 3D Keltool, Direct AIM, DMSL, and RapidTool have been commercialized. Aluminum-filled epoxy, cast kirksite, laminated tooling, RTV silicone rubber, and sprayed metal tooling are available, but are not necessarily vendor-specific.
Most of these methods are relatively new, although not all of them. Aluminum-filled epoxy and Keltool, for example, have been available for more than 20 years. The fast production of RP patterns has made these two processes more viable today because both are pattern-based. Some RT processes will become commercially successful, if they have not already, while others will fail miserably in the market place. Most technologies require years, if not a decade or more, to fully develop. If we become impatient and do not support these methods, they will surely disappear. If we instead have a positive outlook and encourage their development and application, there is a chance that organizations—possibly yours—will benefit from them in the future.
In the short term (3-6 years), the indirect approaches are most likely to succeed. In fact, some of them have already proven to work very well for the molding of certain types of parts. In the long term (7-12 years), direct approaches will become a more viable option due to the potential time-savings that they offer. Direct methods of RT provide the opportunity to reduce the number of steps, thus improving turn-around time.
Methods of RP are developing at both ends of the product development spectrum. At the front end, 3D printing for concept modeling has a lot of promise. At the back end, the technology is evolving from prototyping and tooling to rapid manufacturing.
Indeed, rapid manufacturing (RM) may be the next frontier. Already, some companies are beginning to use RP-driven processes to manufacture end-use products, albeit in relatively low quantities. It’s unlikely that RM will ever reach the production capacity of processes such as plastic injection molding or sheet metal stamping, but for some companies, this may not matter. Not all manufacturers produce and sell in volumes of millions, or even hundreds of thousands. Consider, for example, companies that produce replacement limbs and other prosthetic devices. Also, consider companies that manufacture products for space exploration.
An interesting trend is the growing desire for product variety among consumers. As a result, companies must design and manufacture a higher number of products in a given product family, but at lower quantities. Another dynamic is the movement toward mass customization, where ultimately, a production run will consist of a single product. For some product lines, such as inexpensive disposable razors and ballpoint pens, this is unlikely to happen, but for expensive products with relatively long life cycles, it is almost inevitable.
As the idea of product variety and "customerization" develops, RP technology will play an important role. Not only will it help companies streamline the design and prototyping process, but it will help produce one-off manufactured parts—an inherit strength of RP. While the mechanical properties of RP materials are not suitable for all products, some of the newer epoxy resins, and certainly nylons, ABS plastic, and composite materials, offer impressive strength. There's no question that some products will be much too demanding, but for others, one or more of the growing list of RP materials will be more than adequate for the task.
Some may question the surface finish of RP parts when considering them for use as production parts. The stair steps are getting smaller as the thickness of the layers decrease, but they are still noticeable. Consider, however, that many parts in a product are hidden from view, such as those found inside an electronic enclosure, office machine, or the panel of a car door. This eliminates any negative impact of the part's appearance.
In addition to mechanical properties and surface finish, cost of the manufacturing process is a consideration. RM may not be practical for large parts, but for small ones, there is compelling evidence that RM is less costly than traditional manufacturing approaches, for relatively small volumes of parts.
Professor Philip Dickens of De Montfort University in the UK performed an interesting study in 1997. One of its purposes was to compare the cost of traditional plastic injection molding to that of RM using methods of RP. To make the comparison as authentic as possible, Dickens worked with Flymo, a manufacturer of lawn mowers. Dickens and the company selected an impeller, hub, and blade to use in the study.
Flymo carefully determined the cost of producing the injection-mold tooling and molding a given number of plastic parts. Dickens worked with others to produce the three parts on several RP systems. This gave him the information needed to calculate the cost of producing these three parts in volume.
The break-even point for the biggest part, the impeller, was 315 parts. In other words, the cost to produce 315 impellers was the same using both injection molding and RM. So, if there was a requirement for less than 315 parts, RM would be the least expensive of the two. The cost of the injection molding included the design and production of the mold.
The numbers look even better for RM when producing smaller parts. The break-even point for the hub was 2,800 parts. The break-even point for the blade, which is much wider but not nearly as tall, was 6,150 parts.
The cost of RP systems is expected to decline over time, so Dickens estimated what the break-even points might be in five years. He believes that they may be in the range of 1,750, 22,000, and 46,500 for the impeller, hub, and blade, respectively. Even if these cost improvements do not occur, RP is affordable today to manufacture small parts in quantities of thousands.
RM provides other benefits, too. Using RM, you do not have to wait weeks or months for tooling. Today's RP systems permit you to build parts as soon as the design data is complete, enabling you to deliver them to the customer the same week. Another benefit of RM is the ability to more easily make engineering changes up until the product is in production or even after it is in production. A change would require sending a new version of the STL file to the machine—that's it. With injection molding, engineering changes are typically expensive, both in money and time.
The idea of RM is fascinating, but it will take time to develop. One consideration is the cleaning of the parts after taking them out of the machine and removing the support structures, for those systems that require them. Stereolithography and FDM require support structures, so for some shapes, RM may not be practical. In August 1999, Stratasys introduced a new system, the FDM3000, which uses a new method of support structures called WaterWorks. It is a "hands free" approach to removing support structures by immersing the part in a water-based solution. Powder-based processes such as Z Corp's Z402 system and laser sintering from DTM and EOS, do not require support structures.
And finally, the speed of fabricating production parts using an RP process will be critical to the success of RM. In 1997, injection molding was about 100 times faster than most RP processes, according to Dickens. In the early 1990s, an RP system could process about 16 cubic centimeters of material per hour. Today, a fast RP system can process more than 1,000 cubic centimeters per hour—an improvement of 60 times. As system developers work to further enhance the speed of their systems, it's likely that we will see additional speed improvements over the next few years.
Where does CNC machining fit in? For many applications, it will remain the technology of choice. It is a proven and widely accepted option that offers a wide selection of materials. RP technology has improved over past several years, but so has CNC software and hardware. For large metal parts and mold inserts, CNC delivers and many companies will continue to use it successfully. As 3D printing, rapid tooling, and rapid manufacturing develop and mature, progressive organizations will look to them for solutions that give them an edge over the competition. Moving at the right time and to the right technology will be the key for thousands of companies around the world.
Note: Some of the information presented in this paper was excerpted from Rapid Prototyping & Tooling State of the Industry: 1999 Worldwide Progress Report. To learn more about the 221-page report, contact Wohlers Associates, Inc. at wohlersassociates.com. This web site also provides access to more than 73 articles, papers, reports, and other documents on RP, RT, CAD/CAM, and reverse engineering. It includes links to more than 182 RP system manufacturers, CAD/CAM vendors, service bureaus, universities, and other organizations focusing on rapid product development.
Copyright 1999 by Terry T. Wohlers