Prototype or product? Rapid manufacturing is closer to mainstream

There is promise of growth in the rapid prototyping industry. RP technologies have immense potential for future applications such as rapid manufacturing. However, materials, speed, and resolution are ongoing challenges.

The potential of rapid prototyping seems limitless when talking to Mervyn Rudgley, 3D Systems? (Valencia, CA) senior director of product management. He speaks of the future of rapid prototyping, when it won?t just be in the office, but at home too. Instead of purchasing products, you will purchase a design and materials, and ?print? your own product on your home rapid prototyping equipment. Sound farfetched? Perhaps, but this type of vision is what has kept rapid prototyping suppliers plugging ahead, even though sales aren?t what was originally anticipated when the technology was first developed.

3-D Printing
The ability to save money in the design stage of product development is a powerful incentive for the rapid prototyping process. Terry Wohlers? Rapid Prototyping & Tooling State of the Industry Annual Worldwide Progress Report 2002 (Wohlers Assoc. Inc., Fort Collins, CO) presents a cost-of-error model. It predicts that for every $1 error not corrected at the modeling stage, the mistakes will cost a manufacturer up to $10 at the mold stage, and up to $100 at the serial production stage.

The most inexpensive and popular rapid prototyping technologies on the market are 3-D printers. 3-D printing equipment is relatively low-cost, easy-to-use, and usually fits on a desktop.

Mary Stanley, Dimension product manager at Stratasys (Eden Prairie, MN), says that 3-D printing is primarily used in the design stage of the product. Recent advances in the technology, such as the Dimension, launched in early 2002, are allowing businesses to create a prototype that can be tested for form, fit, and some function. The Dimension uses durable ABS, has a breakaway support system, and is designed for workstation and network access much like a standard laser printer. It uses Catalyst software and runs on Windows NT, 2000, or XP, and is priced under $30,000.

Craig Wright, an engineer at 21st Century Plastics Corp. (Potterville, MI), a 17-machine custom injection molder, says that the Dimension is a useful tool. When working with a customer on a seating product, Wright says not only did the company provide prototypes quickly, but they also could test for function. ?Our customer had a need for a dampening mechanism designed specifically for its product. The design was modified, and the second prototype was produced and put into testing with the models created using Dimension. These models underwent torsional forces similar to the actual application, and are currently being evaluated for effectiveness,? says Wright.

Z-Corp. (Burlington, MA) offers 3-D printing technology that uses two proprietary powders: one starch-based and one plaster-based. Michael Jahnke, global manager of prototyping resources at Motorola (Libertyville, IL), says the company uses Z-Corp.?s Z406 system primarily to develop cell-phone designs. ?We use the 3-D printer frequently during the early stages of program development, and we?ve found that it allows for greater participation among multiple team members early on.?

In addition to use by design engineers, prototypes are also used for human factor and ergonomic studies, according to Jahnke. The company also has a stereolithography (SLA) machine from 3D Systems and two high-speed CNC machines from Defiance (Defiance, OH). He says once the design ?gets further down the pipe? they turn to these machines, but in the beginning the main advantage is the 3-D printer?s speed and cost. ?The resolution is fine for early development, but you can?t really do fine details and thin-walls. And right out of the box, it?s not as strong as SLA,? Jahnke says. ?But, we use it for what it?s meant to be used for?a quick, cheap study for multiple design iterations.? According to Jahnke, the cleanup for the Z406 is minimal, although a fine dust from the powder does settle on anything nearby during use if the machine is not kept clean.

The Thermojet from 3D Systems is also designed for form and fit but not function. ?The technology is not designed to provide functional materials,? says Rudgley. The Thermojet produces prototypes of a wax-type substance that is part thermoplastic, part paraffin wax. ?The Thermojet has a huge impact on the understanding of a design,? he says. ?Once the design is developed, it?s time to move on to a functional prototype.?

What?s Out There
One of the most well-known prototyping technologies in the industry, SLA is designed to produce high-precision prototypes in functional materials and patterns that can be cast or used to make tooling for short runs of a part. SLA can provide testing for mechanical operation of a mechanism and the ability to withstand heat stresses and show flow characteristics. ?The material is an epoxy, so there are some limitations to the mechanical strengths of the materials,? says Rudgley of 3-D Systems.

Enter the company?s selective laser sintering (SLS) technology. SLS uses nylon materials, which are a better match to injection molded plastic. SLS uses laser energy to sinter powdered material to create a part.

Numerous RP technologies are available. Cubic Technologies (Carson, CA) offers the laminated object manufacturing (LOM) process, which laser cuts layers of adhesive-coated material and bonds layer by layer until a 3-D model is produced. Objet Geometries (Rehovot, Israel) uses a multiple jet technology that applies a special photopolymer material on a build tray. Each layer is cured by UV lighting, eliminating the need for an additional post-modeling curing process. MCP Systems (Fairfield, CT) offers its vacuum casting technology for duplicating plastic, wax, ceramic, and silicone prototype castings from rapid prototype models.

Rapid prototyping service bureaus typically offer the services of more than one kind of equipment. Distrim2 (Marinha Grande, Portugal), a Vangest company, provides rapid prototyping services using two five-axis high-speed milling centers, two three-axis high-speed milling centers, an SLA system, and three MCP vacuum casting machines, and low-pressure reaction injection molding (RIM) equipment.

Victor Oliveira, CEO of Distrim2, says that it constantly tries to update its rapid prototyping equipment to keep up with customer demands, and that it is always in search of the highest quality product. ?We are still limited by the quality of the equipment. Even if the level is extremely good, our goal is perfection, and because we can?t achieve the level of tolerances we have in serial production, we are not satisfied with the available equipment,? says Oliveira.

RP manufacturers are well aware of the demand for high-quality prototypes. ?As companies scramble to remain competitive, they look toward new technologies that will reduce time to market, and lessen the cost of error,? says Daniel Cohen, marketing manager for Objet Geometries.

Stratasys introduced an enhanced fastest-machine-to-date, the FDM Maxum, in March 2002, with increased resolution to .005 inch. This allows engineers to build models with finer feature details and smoother surface finish. The Maxum has the company?s largest build envelope of 600 by 500 by 600 mm (23.6 by 19.7 by 23.6 inches). The machine uses fused deposition modeling (FDM), which applies ABS as a material.

The Maxum?s increased resolution was the result of a collaboration between Stratasys and Fuji Photo Film Co. (Tokyo). Fuji uses the technology to produce compact pocket-camera components that can be functionally tested.

Stratasys also recently introduced an upgrade to its FDM Titan, which builds models from polycarbonate and ABS. The Titan has a build size of 16 by 14 by 16 inches. The upgrade, known as WaterWorks, includes surface-finish resolution and support-removal automation for ABS models. ?The Titan was developed in response to users performing more and more demanding functional tests on their prototypes,? says Stratasys president Scott Crump. ?A carmaker, for example, may want to create a prototype part and bolt it right onto the engine to get performance feedback under realistic operating conditions. There?s a high value to that.?

The Wave of the Future
Rapid manufacturing, as differentiated from rapid prototyping, has long hovered as a possibility that has never quite materialized on a significant scale. According to Terry Wohlers, ?Rapid manufacturing is developing into an intriguing market opportunity. RM may even become the most significant area of growth in this decade.?

Mervyn Rudgley agrees. The company?s SLA technology is increasingly being used to generate patterns for short-run parts or tooling. For instance, if a company needs a short-run of a part, they can produce a soft tool by coating an SLA pattern with silicone rubber, and then pouring a material like polyurethane into the pattern, to produce up to 40 or so parts. As Rudgley points out, ?For some companies, forty parts is the entire production. This could include parts like ATM fronts or casings for certain medical devices.?

There is a significant market for companies that make fewer than 1000 parts in a run. Rudgley cites the aerospace industry as an example. Boeing uses 3D Systems? technology to manufacture air ducts for fighter jets. ?Traditionally, Boeing used rotomolding to make the tubing, but rotomolding requires a tool,? says Rudgley. ?Using our SLS technology, they can make the parts without tooling and with greater complexity.?

According to Wohlers, ?It?s unlikely that RM will ever reach the production capacity of processes such as injection molding, die casting, or sheet metal stamping, but for some companies, this may not matter.?

The consumer increasingly wants ?more customized products, shorter runs, more complex data in a shorter time,? says Rudgley. This trend could create an even larger market for rapid manufacturing.

More Materials Please
Rapid manufacturing seems to be the wave of the future, but one dilemma stands out in both rapid prototyping and rapid manufacturing?material selection. ?In terms of materials, there is still a lot of room for improvement,? says Oliveira. ?Today, this is one of the most important issues.?

?Material is really the key limit,? says Rudgley. ?We only have 15 in our portfolio, and we find that people usually want a material that we don?t have.?

Recognizing this need, 3D Systems has developed some more durable materials to accompany its technology, including DuraForm polyamide and glass-filled polymers that were developed specifically for creating thermoplastic parts that withstand aggressive functional testing. A preliminary Accura LaserForm ST-2000 material is a stainless steel composite developed to produce tooling inserts for injection molding applications. The preliminary Accura SI 40 material is the first SLA material to mimic nylon 6:6, allowing parts to be used in high-temperature applications without brittleness or breakage.

?The number one thing users want is better materials?durable, functional plastics?real engineering plastics used in end products,? says Crump from Stratasys. The company is developing the use of polyphenylsulfone with its FDM prototypes. ?The selection of materials from Stratasys will offer users such performance characteristics as improved impact strength, strength at high temperatures, flame-retardant qualities, sterilization capability, and resistance to oils, gasoline, chemicals, and acids.?

Michael Littrell, president of C.ideas Inc. (Cary, IL), a service bureau, says that the availability of materials, whether it is a proprietary issue, or an availability issue, is a definite limit to the technology. He adds that along with improved materials, faster speeds and higher resolutions are at the top of the list too.

Oliveira sums up the current state of affairs and points to the future. ?More than actual technology improvements, which have been very significant in the last few years, the big difference is in the clients? expectations and perception of what a prototype should be. Today we are expected to produce a component that is actually identical to the final part, faster, cheaper, and with the best material.?