Selecting the appropriate rapid prototyping system for an engineering technology program

Journal of Engineering Technology, Spring 2002 by Sriraman, Vedaraman, DeLeon, John, Winek, Gary

Abstract

Modern rapid prototyping (RP) systems can be a valuable tool in an engineering technology curriculum. These systems can range in price from basic configurations that cost approximately $8,000 to more extensive platforms priced over $400,000. These systems also differ in suitability for specific curricular applications, ease of use, safety considerations, and the cost of supplies, maintenance, and installation. To effectively teach the various RP applications used in industry, it is essential that educators select the appropriate technology. This paper will outline a methodology for selecting RP systems for educational use, provide a list of RP machines, specifications and manufacturers, and describe the application of the proposed methodology at

Southwest Texas State University. A summary of RP applications at other institutions is also provided for comparison.

Introduction

Competitive pressures faced by manufacturing companies have led to development of a host of tools and procedures designed to drastically reduce time-to-market cycles, including computer-aided design (CAD), computer-aided manufacturing (CAM), computer-aided engineering (CAE), computer numerical control (CNC), investment casting, virtual prototyping, and rapid tooling.1 These tools, commonly known as time-compression technologies, are based on the concept of rapid prototyping, a broad term used to describe several processes that create physical models directly from a CAD database. RP systems use a variety of techniques to form models, including stereolithography and fused deposition modeling (FDM).2 Detailed descriptions of various RP systems, polymer chemistry, CAD-based requirements, and RP applications are available in the literature.3,4 Charles Hull coined the term stereolithography, or three-dimensional (313) printing, which uses an ultraviolet laser to selectively cure layers of photopolymer. Hull patented the process in 1986 and founded 3D Systems, Inc., which in 1987 developed the first commercially available RP system in the world, the SLA-1.5 Approximately nineteen manufacturers worldwide have since developed RP systems, and products from eight of these manufacturers are commonly available in the U.S.6

The growing importance and acceptance of RP technology in the U.S. is evident in the following statistics. The Rapid Prototyping and Tooling: State of the Industry, 1998 Worldwide Progress Report stated that close to 50% of RP installations worldwide are in North America.7 Several of the most widely sold RP machines are from U.S. manufacturers, and of the 5449 machines sold from 1988 to 1999, 4412 or 81% were from U.S. companies.6

Engineering technology educators play a critical role in providing students with meaningful learning experiences in the tecnologies currently used in industry. In the past, technologies and tools such as solid modeling, CNC, CAE, programmable logic controllers, robotics, and coordinate measuring machines have been successfully incorporated into the engineering technology curriculum. The same must be done for RP. However, selecting the appropriate RP system can be quite a challenge, as educators must choose from among nineteen different RP system manufacturers, various processes and materials, and units priced from $8,000 to over $400,000. This paper establishes a process for selecting a RP system that meets educational goals while considering cost, maintenance, ease of use, and safety.

Curriculum Needs

The curriculum needs of a program should be the single most important factor when considering the purchase of a RP machine. In 1998 it was reported that 28% of all RP models were being used for fit and function applications, 36% served as visual aids for engineering, tooling, quotes and presentations, and 25% were used to make patterns for prototype tooling and metal casting. These technological applications can serve as inputs for determining how RP should be integrated into the engineering technology curriculum, but they should also be reconciled with the special characteristics of an academic environment, such as curriculum need, ease of use, safety, purchase price, and operating and maintenance costs. Thus, several criteria must be adequately addressed before incorporating RP into a curriculum.

It is particularly important to consider the purpose of the RP model, which depends upon the curriculum. A two-year program in engineering design graphics may require only a concept RP machine for form and fit verification, while a four-year program in manufacturing engineering technology may need rapid tooling applications. RP selection also may be influenced by the specific discipline within a curriculum. Thus, the curriculum provides the first essential input to the selection process.

Once the curriculum-based needs have been established, the RP system that best suits those needs can be selected. For example, programs in engineering design graphics or mechanical engineering technology will, in general, use RP models for visualization of form and fit and for limited functional testing. If this is the sole or predominant use for RP, there are several basic systems available for less than $50,000, as shown in table 1. The JP-5 systems from Schroff Development, including 3D modeling software, are priced as low as $7,900. These particular systems offer manual stacking and adhesion of the paper layers, so they may not be as fast or as accurate as other processes. If the program under consideration is manufacturing engineering technology, RP models can be applied over the entire product cycle, from design through manufacturing. In this case, RP will also be used to generate rapid tooling for processes such as metal casting, injection molding, and prototyping tooling. However, system accuracy and material selection must be carefully considered, since prototypes are cast from wax or other materials that are burned out of a mold.