Chapter 2
How It Works
The technology of 3D printing is a bit like cooking. You have a technique or process (Italian or Chinese cooking) that influences the specific materials (pizza dough or rice) used and dictates the hardware (pizza oven or wok). It has software (a recipe) and a file format (cooking instructions, such as the oven temperature and time), all of which you use to make something to eat. In 3D printing, the technique or process dictates the materials, hardware, software, and file format you will use to make the object you want. And just as with cooking, the hardware is a lot bigger if you cook for hundreds of people rather than for just you and your family. Some 3D printers would barely fit in your living room, while others are small enough to fit in your backpack.
The Basics
Like cooking, 3D printing relies on a set of instructions to create a final product using specific materials and tools. And like cooking, it is something you can do at home.
The ingredients of any 3D-printed object include a process, materials, hardware, software, and file format. How do these ingredients interact in 3D printing? With the software, you create a digital image of the object you want to create (the recipe). You then save the digital image in a 3D printing file format (the cooking instructions). The file format does two things: it slices your digital object into thin horizontal slices, or layers, like a deli worker slices cheese from a large cheese block. The file format then provides instructions to the hardware—the 3D printer—for how to add each layer on top of the previous layer so the printer can build the physical object you designed on your computer. Depending on the 3D printing process, the printer will squeeze melted material out of a nozzle (like a baker squeezing icing out of a cake-decorating tube). Or a laser will harden and deposit material layer by layer (like chocolate sauce that instantly hardens when it hits your ice cream).
The Process
The FDM process falls in the squeezer category. SLA and SLS processes are hardeners. (Reminder: fused deposition modeling, FDM, is also known as fused filament fabrication, FFF, when the process is used by a non-Stratasys company.) FDM uses strands of brightly colored thermoplastic filaments coiled around spools like thick thread. The printer melts the filaments strand by strand, and the nozzle deposits, or squeezes, the melted filament onto the printer platform layer by layer to build the object. Engineers, designers, and hobbyists use FFF for a variety of purposes, including prototypes and finished products. Other squeezer printers include laminated object manufacturing (LOM), bioprinters, and printers of electronics.
SLA relies on a vat of resin, a syrup-like liquid. The printer’s UV laser cures, or hardens, the resin, one layer at a time, into a specific shape. The curing is somewhat like flash freezing syrup. The shape appears to emerge from the vat of resin. Engineers and other professionals use SLA to create finished products as well as prototypes in a variety of fields, including aerospace, automotive, medicine, dentistry, arts and entertainment, culinary, architecture, and energy.
SLS requires a vat of powder, something like a tub of fine sand. High-powered lasers melt the powdered particles together. They then form a hardened, solid mass. With SLS, you actually pull your creation out of the remaining powder as if you were pulling a toy out of sand at the beach. Engineers and designers use SLS to create objects with complex shapes and highly durable parts and molds in plastic, ceramic, glass, and metal. SLS works for a variety of fields including aerospace and engineering. Other hardener printers include digital light processing (DLP) and selective laser melting (SLM).
SLS technology 3D prints objects in a bed of powdered material. A laser beam sinters (heats) or melts certain areas of the powder to build the object layer by layer. As it is printed, the rest of the powder supports the piece. Manufacturers then use an air nozzle, a sand blaster, or a simple brush to remove the powder support when the piece is finished.
Multi Jet Fusion
In the early twenty-first century, several creators of ink-jet printers—the types of printers we use to print words or images on a page—have also developed new 3D printing processes. In 2014, along with its ink-jet printers, HP revealed its new 3D printing process, called multi jet fusion. Industry reports, along with HP, claim that the multi jet fusion technology works ten times faster than the fastest 3D printers.
Multi jet fusion also falls in the hardener category. First, the printer deposits a layer of material onto a platform. Then it drops additional material at thirty million drops per second to build the object, layer by layer. In some cases, the printer builds multiple objects at a time. Finally, it fuses the materials and then heats and cools the object exactly where it needs to make a smooth-edged, well-defined object.
HP provides this technology to aerospace, automotive, medical, dental, life sciences, and a variety of other industries. What material can you use? HP says anything. Companies work with HP to print their materials, including electronic, multi-material, and multicolor structures.
The Materials
FDM printing uses plastic filaments such as these. Specialty or composite 3D printer filaments combine thermoplastics with metal powder, carbon fiber, wood, and glow-in-the-dark compounds to create hybrid materials for printing.
The three most common 3D-printed materials are thermoplastic filaments, UV curable resins, and anything that can be made into a powder (metal, ceramic, or plastics). As 3D printing becomes more common, people want to use a wider variety of materials. These include metal and plastic combinations, carbon-fiber and plastic composites, clay, plants, human cells, and even chocolate to name just a few. And 3D technology can use recycled materials. Organizations such as ProtoPrint, the Plastic Bank, and the Perpetual Plastic Project collect and convert plastic waste (such as milk jugs and water bottles) into 3D printer filament. Or you can recycle your 3D plastics with products such as ReDeTec’s ProtoCycler. Meanwhile, innovators are looking for more ways to recycle materials other than plastic for 3D printing.
The Hardware
The 3D printers that you’ll find in industrial settings are usually large and expensive. They cost about $100,000 to more than $1 million. Smaller, more affordable printers for home or office cost about $1,000, sometimes more. The 3D printing industry began with the larger industrial printers for manufacturers.
The size of the printer determines the size of what you can print. So the geometric shape of the object can’t be larger than the 3D printer itself. If it is, you’ll need to find a larger printer or do multiple print jobs and then assemble the printed parts. The maximum length, depth, and height that the printer can print is called the build volume. The build volume is expanding as innovators come up with new ideas. For example, robot printers, such as Arevo Labs’s Robotic Additive Manufacturing Platform (RAMP), released in 2015, can print anywhere, any size. For engineers, RAMP offers more design possibilities and larger sizes for printed objects because the robot is not limited to the dimensions of a conventional 3D printer.
Autodesk and other companies are experimenting with 3D printing systems that use multiple printing heads to help a manufacturer make a large object in one print job. Autodesk is working on the software for this hardware in hopes that manufacturers of 3D printers for engineers, professionals, and the home market will jump on board to build these multiple-printhead printers. The software breaks up large designs into multiple sets of instructions that can then be sent to multiple printheads simultaneously. The benefits to this approach include printing larger objects, taking less time to print small objects, and doing multiple jobs at once by swapping out printheads for other tools. A robotic hand, for example, could help the printer by repositioning parts of the object being printed to allow the printer to continue printing.
The Software
The software for 3D printing started with CAD tools that required advanced engineering skills to use. In the twenty-first century, anyone with a computer can use CAD, freeform modeling, sculpting, and 3D immersive design tools. CAD tools such as SketchUp and Tinkercad use geometric shapes to build 3D models. Freeform modeling tools allow designers to create many different shapes. Anything you can draw, you could potentially 3D print using freeform modeling software such as 123D Creature or Blender. Sculpting tools work like clay, allowing a designer to push, pull, pinch, and grab elements to form 3D models digitally. Sculpting software includes 123D Sculpt and Leopoly. Immersive design tools include software and hardware that combine 3D scanning, modeling, and printing to move between reality and digital 3D worlds almost seamlessly. One popular immersive tool is HP Sprout.
You can play with many of these software tools for free. Check out resources such as the 3D Printing for Beginners website for descriptions and links to download the software. The more you play, the more you can add your voice, innovations, and skills to the 3D manufacturing revolution.
With CAD software, users can design just about anything for 3D printing. The hardware fits easily on a desk or tabletop.