by J Horvath · Cited by 2 — 3D printers and the open source software that runs them. he field is changing metaphor you will see in this book is that 3D printing is about as complex
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vContents at a Glance About the Author .. xviiAbout the Technical Reviewer . xixAcknowledgments . xxiIntroduction xxiiiPart 1: Open Source 3D Printers . 1Chapter 1 : A Brief History of 3D Printing .. 3Chapter 2 : The Desktop 3D Printer . 11Chapter 3 : Open Source .. 21Part 2 : The 3D Printing Process 31Chapter 4 : Making a 3D Model . 33Chapter 5 : Slicing a 3D Model .. 47Chapter 6 : Driving Your Printer: G-code .. 65Chapter 7 : Material Considerations .. 77Chapter 8 : Case Studies .. 89Part 3 : 3D Printing Meets Traditional Prototyping .. 111Chapter 9 : Moving to Metal . 113Chapter 10 : Large Prints and Post-Processing . 129Chapter 11 : Troubleshooting . 137www.it-ebooks.info
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CONTENTS AT A GLANCE vi Part 4 : Using Your Printer . 149Chapter 12 : Printers in the Classroom .. 151Chapter 13 : Scienti˜c Visualization 165Chapter 14 : Futures . 175Appendix A: Typical Printer Settings .. 183Appendix B : Links and Resources 189Index 193www.it-ebooks.info
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xxiii Introduction 3D printers have been around for about 30 years, but you would never know that from the current explosion in both 3D printers and the uses for them. Although some of the more extreme hype in the ˚eld will go away in due course, 3D printing really does enable some new ways of thinking about creating products, particularly custom ones. What is new is the availability of low-cost 3D printers (costing from a few hundred to a few thousand dollars). ˜ese lower-cost machines have the promise of making the front of the product-development process much more e˝cient and enabling distributed manufacturing. ˜is book focuses on these consumer-level printers and their applications. In particular, the emphasis is on open source 3D printersŠmachines whose software and hardware designs are freely shared online. 3D printing can be de˚ned pretty simply: creating an object by building it up layer by layer, rather than machining it away, the way you would by making something from a block of wood, or squirting something into a mold, as you would for injection-molded plastic parts. Its ˙exibility and the sheer magic of seeing something built from nothing have captured people™s imaginations, and it is clear that surprising applications will continue to pop up for years to come. ˜is book is intended for several audiences. First, it is meant to be a self-contained tutorial on consumer 3D printers and the open source software that runs them. ˜e ˚eld is changing very rapidly, though, and as such you should expect that the details of the software and hardware will shift away from the book™s descriptions. A recurring metaphor you will see in this book is that 3D printing is about as complex as cooking. In cooking terms, you will ˚nd that this book has a bias that shies away from providing recipes to follow exactly and instead leans toward teaching you how to cook over the long haul. ˜is book also is intended to be used as a text for a semester-length class or university extension certi˚cate series covering 3D printing, its applications, and its place in manufacturing innovation. It might be paired with an in-depth class on 3D computer-aided design (CAD) software for students interested in engineering and industrial or product design applications. Similarly, it might be paired with in-depth instruction in one of the sculptural 3D-modeling programs for students developing skills in 3D animation or ˚ne art. Part 1 (Chapters 1Œ3) of the book gives background on the history of these printers, talks about how the hardware works, and gives some insight into the open source and do-it-yourself movements that nurtured the propagation of the consumer 3D-printer industry. Part 2 (Chapters 4Œ8) is the nitty-gritty tutorial on the work˙ow of using a 3D printer: developing a 3D model, slicing it into layers that the printer will create one at a time, and controlling the printer in real time. Part 2 also reviews available materials and walks through some case studies. Part 3 reviews how you can take your 3D print and post-process it to improve the surface ˚nish, create larger projects, or even cast a metal part from your printed one. Part 3 covers troubleshooting, too, just in case you got a little too ambitious for your printer™s linking . Finally, in Part 4 you will read about how educators, scientists, and others are using 3D printers, and where the ˚eld may go in the future. If you are just starting your exploration of the ˚eld, welcome. Hopefully, this book will be a good guide for you, and you will ˚nish it ready to take on challenges and try to help build this new frontier along with us. www.it-ebooks.info
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PART 1 Open Source 3D Printers The first part of this book introduces you to open source 3D printers. A user makes a number of tradeoffs choosing an open source, fihackablefl design, and these tradeoffs and the design rationale behind them are the focus of the first three chapters. Chapter 1 is a brief history of 3D printing, with a focus on consumer printing. Chapter 2 talks about how these printers work and why there is a sudden blooming of interest in the technology. Chapter 3 rounds out this section with a discussion of the open source philosphy and the pros and cons of being a part of an open source 3D-printer community. www.it-ebooks.info
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CHAPTER 1 A BRIEF HISTORY OF 3D PRINTING 4As it gets longer and wider the shell gets thicker, too, so that it does not become fragile. The shell is secreted and condensed out of materials in the creature™s en vironment instead of laid down with a nozzle like t he printers you will read about in this book, but the results can still be pretty remarkable. For more details, see www.scientificamerican.com/article/how-are-seashells-created/. Similarly, many rock formations in the southwestern United States were laid down when ancient oceans built up layers of silt. The resulting sandstone has since been carved away by wind, rain, and plant roots. Figure 1-2 is an example of the final result of the processes that first build up material one layer at a time and then erode some of it away. Figure 1-1. Seashells are a product of natural fi3D printingfl Figure 1-2. Another example of natural 3D printing in Cave Valley, Zion National Park. Photo courtesy of Niles Ritter www.it-ebooks.info
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CHAPTER 1 A BRIEF HISTORY OF 3D PRINTING 5When people watch a natural process (like the ones resulting in the shells in Figure 1-1 or the sandstone in Figure 1-2), a few might have been inspired to create a fabrication process that will work the same way. Next, let™s look at some traditional manufacturing processes that foreshadowed 3D printing. Historical Additive Manufacturing 3D printing is a form of additive manufacturing . Additive manufacturing starts with nothing and builds up parts by laying up material on some sort of build platform. A lot of conventional manufacturing is subtractive, meaning that you start with a block of material (like metal or wood) and start cutting away material until you have the part that you want plus a pile of sawdust or metal shavings. The rock formation in Figure 1-2, as we noted, was a bit of both. Some types of additive manufacturing have been around for a long time. A very simple example is the humble brick wall. A brick wall is built up one brick at a time, with the addition of a bit of mortar, based on either a formal plan drawn by an architect or engineer, or perhaps just built out of a contractor™s head, if the job is routine enough. All the steps you will see in 3D printing are there in building a brick wall: designing a desired end product, planning out how to arrange the layers so that the structure will not fall down while it is being built, and then executing the product one layer at a time. 3D printers add the elements of robotic control to this process of building an object up a layer at a time. Types of 3D Printers Conceptually, 3D printers work similarly to making a brick wall (although they are a lot more flexible in what you can build). One way or another, 3D printers start with a computer model of an object and then use that model to control a robotic device that uses one of three technologies to lay up an object. Broadly speaking, there are three categories of additive manufacturing: selective binding, selective solidification, and selective deposition. Typically, people refer to these technologies by the acronyms SLS, SLA, and DLP, as discussed in this section. We are defining these three categories here to keep the sheer number of technologies understandable and to organize them a little. Selective binding technologies make a 3D printed object from a powder (metal and gypsum are common materials) by applying binding agents or heat to fuse the powder™s particles together. An example is SLS (selective laser sintering) in which a laser is used to fuse one layer of powdered material at a time. The first layer is fused to a platform, and then another thin layer of powder is added above the first, and so on as the model is built up. The powder acts as a supporting medium for the print, so that very complex and delicate prints can be created. The fine powder can be hard to deal with, though, and the printers tend to be expensive. Selective solidification makes a solid object from a vat of liquid by selectively applying energy to solidify the liquid a layer at a time. Again, typically a first layer is created on some sort of build platform, which then moves down into the liquid (or, in some cases, a build platform pulls up out of the liquid). One example is stereolithography (SLA), which uses UV light to solidify a resin with a laser, or sometimes a digital light projection (DLP) imager, to harden a whole layer at a time. Either way, the model often needs to be cured afterwards, and the resin can be messy to deal with. Desktop SLA printers are starting to come onto the market now but are more expensive than the filament-based printers described next. Selective deposition techniques only place material where you want it. The filament-based printers we focus on in this book work this way, by melting a filament and then placing the melted plastic to create an object precisely. There are also 3D printers that inkjet-print liquid resin, which then is UV cured. Printers that use a powder mixed with a binder are arguably a hybrid of selective binding and selective deposition. Which technology makes the most sense for you to use depends on several things: your budget, the model™ s complexity, and the finest detail that is necessary. B y and large, cheaper technologies produce less-detai led results, although all the technologies are evolving rapidly. This book focuses on the lower-cost end of the spectrum: printers that melt a filament and then deposit the material. The other technologies typically are not appropria te for the average home user because of cost and materials-hand ling issues, although this may change over time in t his rapidly evolving field. www.it-ebooks.info
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CHAPTER 1 A BRIEF HISTORY OF 3D PRINTING 6Tip If you need high resolution for your final project, you might choose to have a consumer printer at home to develop prototypes and iterate a design. You can then send a print to a service bureau to be printed on an expensive machine for you elsewhere and then shipped.The term 3D printing is actually a bit misleading because people tend to think of their 2D inkjet consumer printers and make extrapolations that are not really accurate. In reality, a 3D printer is a small robot factory. You start the manufacturing process, and (with luck!) a part emerges after a while without any human intervention. However, there are many steps involved in preparing that print; you are not just ficlicking Print.fl Those steps and associated design decisions are the focus of Chapters 4 through 7. The rest of this book will primarily focus on consumer-level printers that melt plastics and then extrude the plastic a layer at a time. The next section briefly reviews the evolution of these printers over the last 30 years or so. To distinguish the printers developed over the last 30 years from the more general additive manufacturing, we will use the term robotic 3D printers . This is not commonly used terminology, however, and after the next section we will simply call them 3D printers , assuming the clams (and bricklayers) of the world will not object to being excluded. Tip This chapter reviews the history and technologies of 3D printing very briefly. If you want more detail, Christopher Barnatt™s book 3D Printing: The Next Industrial Revolution (CreateSpace, 2013Šavailable from www.explainingthefuture.com) contains good reviews of the various technologies, their histories, and how they work. The Early Days of Robotic 3D Printers Charles W. (Chuck) Hull is generally credited with developing the first working robotic 3D printer in 1984, which was commercialized by 3D Systems in 1989. These machines were SLA systems (described earlier in this chapter), and many large commercial machines still use this technology. Other early work was taking place at the Massachusetts Institute of Technology (MIT) and University of Texas. A flurry of patents followed in the early 1990s for various power-based systems. These systems squirt a binder very precisely on the surface of a vat of powder to create layers (again, with a downward-moving platform). Alternatively, a laser can be used to fuse the powder together (in SLS, as explained earlier in this chapter). SLS patents became the basis for Z Corp, another early printer company that created large industrial printers. Z Corp is now part of 3D Systems. Meanwhile, S. Scott and Lisa Crump patented fused deposition modeling (FDM) in 1989 and co-founded the printer manufacturer Stratasys, Ltd. This technology (more generically called FFF, for fused filament fabrication) feeds a plastic filament into a heated extruder and then precisely lays down the material. When key patents expired in 2005, this technology became the basis of the RepRap movement described in the next section. There are 3D printing technologies that can print at the molecular level (called two-photon polymerization , which uses femtosecond pulsed lasers to fuse a powder). These are documented mostly in scientific literature at the moment. At the other extreme, it is possible to print large concrete structures ( contour crafting, developed at University of Southern California and described at www.contourcrafting.org). Researchers are printing food and even human organs. Chapter 14 covers more advanced technologies. The pace of development in the field is very rapid; new methodologies are being invented both by commercial companies and by academics, and it can be a real challenge to keep up with it all and distinguish between a new capability and a dubious idea. www.it-ebooks.info
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CHAPTER 1 A BRIEF HISTORY OF 3D PRINTING 7The RepRap Movement When some of the key patents expired on the FDM printing method, it occurred to Adrian Bowyer, a senior lecturer in mechanical engineering at the University of Bath in the United Kingdom, that it might be possible to build a filament-extruding 3D printer that could create the parts for more 3D printers (besides readily available electronic and hardware-store components.) Furthermore, Bowyer published the designs for the parts for his 3D printer on the Internet and encouraged others to improve them and in turn post the improved versions. He called this open source concept the RepRap project and obtained some initial funding from the UK™s Engineering and Physical Sciences Research Council. Bowyer™s team called their first printer Darwin (released in March 2007) and the next Mendel, released in 2009 (for more details, see http://en.wikipedia.org/wiki/RepRap_Project). The printers were named after famous evolutionary biologists because they wanted people to replicate and evolve the printers. Files to make the plastic parts were posted online, freely available, with alterations and improvements encouraged. Necessary metal parts were ideally available at a hardware store or able to be made in a garage. In practice, nozzles were available for online purchase pretty early on for people without access to machine tools to make one, and stepper motors were commodity items. The early printers were difficult to put together and to get to print well. In the Czech Republic in 2010, Josef Prusa released a design now called the Prusa Mendel. It simplified the original Mendel design, and after that there was an acceleration in printer designs as people tried out the open source designs, modified them, and posted their own. A fifamily treefl of this period can be found at http://reprap.org/wiki/RepRap_Family_Tree.Then there was a transition from making files for printer parts downloadable to making whole printer kits available for purchase. One of the better-known kits was the MakerBot Cupcake CNC, which started shipping in April 2009. It was superseded by the MakerBot Thing-O-Matic in 2010. These were mostly made of lasercut wooden parts with some 3D-printed parts (plus, of course, motors and electronics). Eventually, MakerBot became one of the earlier commercial consumer printer companies and was purchased by Stratasys in 2013. What really caused a blossoming of different designs, though, was crowdfunding Šwebsites that allow entrepreneurs to put out early stage products and take contributions from the public to fund development and early production. Because key patents for the core technologies underlying filament-based 3D printing had run out, entrepreneurs typically did not have any type of proprietary technology, which made traditional startup funding difficult to obtain. In the next section, you will see how the availability of crowdfunding enabled 3D-printer entrepreneurs to launch their startups. The Rise of Crowdfunding By 2009, 3D-printer development largely split into two camps: those supplying large, industrial printers (typically with some proprietary technology) and a big informal network of people working on open source RepRap or similar filament-based consumer printers. On April 28, 2009 the Kickstarter crowdfunding platform launched ( www.kickstarter.com). Kickstarter is one of many crowdfunding platforms that allow an entrepreneur to post a project and ask people to support the endeavor. Various crowdfunding platforms have different rules about the type of projects that are acceptable, and open source 3D printers are a very good fit for crowdfunding because most crowdfunding sites require a clearly defined project. Developing a 3D printer is a project with a natural endpoint, and often a printer is the reward the donor gets for supporting the development. Tip To see the vast variety of technologies on the crowdfunding platforms, go to their sites and search on fi3d printerfl for printer projects and fi3d printingfl for ancillary technologies and design projects on Kickstarter (www.kickstarter.com) and Indiegogo (www.indiegogo.com). This material literally changes every day, and watching projects posted on these platforms is a good way to see what is being invented on the entrepreneurial side of the 3D-printing ecosystem.www.it-ebooks.info
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