This is the last in our series of excerpts from "Better Be Running! Tools to Drive Design Success" by Dr. Ronald Hollis, President, CEO, and Co-founder of Quickparts.com (Atlanta, GA). Written for business managers, the book focuses on manufacturing processes, tooling choices, and production strategies that can help companies bring products to market faster. To order the book, go to www.betterberunning.com .
Fused Deposition Modeling (FDM) is the strongest, but slowest, of the major solid-based additive fabrication (AF) systems that produce plastic parts from cross-sectioned CAD models. Electronic CAD design data is converted to Standard Tessellation Language (STL) format, and then special software slices the CAD model into thin layers and creates build instructions for the machine. A heated head with two extrusion nozzles builds the part, layer by layer, pressing spools of filament through an industrial "hot glue gun." FDM is a unique two-material process that provides major strength to parts. The first nozzle dispenses melted support material that dissolves in water; the second nozzle extrudes the permanent base material. A plastic physical model is made of many micro layers of melted filament that solidifies immediately upon cooling.
Ideal uses: Conceptual and engineering models; patterns and masters for tooling; fully functional prototypes for design, analysis, and testing; durable, closest to real production parts; and vacuum forming tools.
FDM was developed by Scott Crump in 1988 and commercialized by Stratasys Inc. in 1990. The FDM equipment and materials are marketed exclusively by Stratasys in Eden Prairie, Minnesota. Stratasys also makes the Dimension 3D printer, an office version based on FDM technology, which has sold thousands worldwide.
The good news is that FDM parts and durable and functional. In fact, many FDM parts can be used in real working environments. The bad news is that the FDM process is very slow, which drives up the cost of parts.
Step by Step with FDM
First, the operator uses software to slice a 3D CAD model into thin layers in the z-axis. This data drives the extrusion head of the FDM system. Plastic filament on a spool is fed through a heated extrusion nozzle. The machine traces out the cross section of each layer, laying down a continuous stream of molten material that cools almost instantly. The second filament is fed from an adjacent nozzle for support material, which is used to support undercut or overhanging features. After the entire cross section is outlined with melted material, the build platform descends by one layer thickness to make room for the next layer, The layering process repeats until the 3D part is fully built. The temperature of the build chamber is precisely controlled to remain slightly below the materials' melting point so that only a little extra heat is required to melt the filament.
The innovative two-material process cleverly does away with costly post-processing time and the risk of part damage during cleanup.
FDM Applications – Stop and Smell the Glue
Look around you. Signs of FDM are everywhere. The door handle of your car was tested in prototype stage using FDM. The commercial airplane window frame, also prototyped in FDM, was first tested at 35,000 feet to make sure that all passengers would remain safely inside the plane. Components in your city's fire truck engines were vibration-tested using FDM. Your neighbor's Hyundai was designed using FDM to ensure dimensional accuracy and stability. A number of race cars on the major speedways have aerodynamically tested components using FDM prototypes.
FDM is a sound technology with seemingly nowhere to grow. Innovations in machine design and materials are long overdue. However, the process is still thriving, thanks to its excellent material properties that no other technology can touch. FDM is still the best process for creating the most real production parts without tooling. Unfortunately, the slow pace of the process is a real hindrance to designers on a deadline. Because FDM parts can take weeks to build, service providers can't turn a profit on a slow process that builds only one part at a time on a 2D build platform. Original equipment manufacturers with their own prototyping labs can afford to purchase FDM equipment; they keep it running 24/7 to get the most value.
Stratasys still leads AF equipment sales thanks to its 3D printer, Dimension, a stripped-down FDM system. The difference between the FDM system and the Dimension printer specifications is considerable, while the materials they use are essentially the same. The Dimension – good for concept verification – uses a bigger tip and is less accurate, while the FDM system makes functional, full-strength parts with higher accuracy.
Low-Volume Layered Manufacturing
FDM was critical in introducing the concept of layered manufacturing to the industrial world. Low-Volume Layered Manufacturing (LVLM) is a very powerful, evolving trend that continues to merge the worlds of engineering and manufacturing. The LVLM approach extends the use of the additive fabricated part as the actual end-use part for the product. Since this trend is very new, many names have been associated with it, including rapid manufacturing and Direct Digital Manufacturing (DDM), as recently decided by the Society of Manufacturing Engineers. Regardless of the name, the trend is that product developers are using traditional AF processes to produce end-use parts.
The LVLM approach has been the dream of many pioneers since the early days of AF. The capacity to make end-use parts this way would give these dreamers and doers the acceptance and credibility they longed for in the manufacturing world. These pioneers have wanted to be equal with the injection-molding technologies and their place at the "adult table."
Imaging the flexibility to design a part for its purpose without regard to the many constraints that are imposed by traditional manufacturing. Wouldn't it be nice to not give a damn about draft? How about eliminating the need to have any tooling to manufacture the part? This would be a huge savings in time and money. With this new-found design flexibility, you could also consolidate the many parts of your product into more complex and useful parts. This would reduce the part count, simplify your bill of materials, and make the product work better,
So, Alice, what's wrong with this Wonderland? As with all paradigm shifts, there are the seen and unforeseen challenges. The industry is still learning how and when to apply AF for end-use parts. Currently, one of the biggest obstacles seems to be that the parts from these layered manufacturing systems simply are not injection-molded parts. Duh! This puzzlingly obvious statement reveals a cautionary truth: LVLM parts don't look, feel, or, in some cases, act like their injection-molded cousins. Also, LVLM presents a challenge when secondary finishing is needed. Of course, with flexibility there is accountability, so the ability to makes design changes also requires the ability to manage design versions so that you will know what part is actually being used in the world. Lastly, the accepted quality control methods still need to be adapted to handle the variability that can be introduced in the part. At the end of the day, a part is not a part is not a part.
To really drive the evolution of LVLM, the manufacturers of additive systems need to take a focused role in their development programs to address the inherent shortcomings of their processes. The easy-to-identify actions for Stratasys, 3D Systems, and any newcomers include the development of quality end-use materials, manufacturing processes that emulate injection-molded parts, and further education about how to better apply these approaches to product development strategies. These companies must decide whether they are developing systems to make prototypes or to manufacture parts.
So, when do you, the product developer, use this powerful LVLM approach? Currently, it seems that the best applications are for internal parts that will never be seen or heard. Non-critical parts are also good LVLM candidates, as well as parts that can accept variability in their tolerances. Some of the best uses come from situations where you need to get your product to market and don't have time to wait for tooling or you are not ready to finalize the design. The LVLM approach will provide an option to get parts quickly and economically while you continue to make progress in your design.
What does "economical" really mean? With LVLM, you will need to be sitting down when you get your first quote for 100 units. The part price will be a shocker! Instead of low pricing in cents or dollars, your pricing will be in the tens or hundreds of dollars each. The good news is that you don't have to spend $30,000 for tooling and you still get all of the other benefits as well.
About the Author
Ronald L. Hollis is the President, CEO and Co-founder of Quickparts.com, Inc. He has provided the leadership and execution to build Quickparts into one of the fastest growing companies in the U.S. This was accomplished through innovation and accepting the risks to change the way you buy custom parts with instant online quoting. Dr. Hollis and Quickparts are also the recipient of many awards including Ernst & Young Entrepreneur of the Year finalist; Deloitte Fast 500; Inc 500; and 2004 Catalyst Innovator of the Year. He is a graduate of the MIT Birthing of Giants program and served in leadership positions for YEO and YPO. He earned a BSME, as well as a MSE and Ph.D. with a focus in technology-based business from the University of Alabama. Dr. Hollis is passionate about building businesses that apply technologies to solve problems and drive efficiency.