Rapid prototyping

The earliest use of 3D printing was in producing digitally designed objects as prototypes of new designs (see Figure 3-1). The advantages of rapid prototyping with additive manufacturing include the following:

• Evaluating a design while it’s still in the computer
• Creating a solid prototype that can be handled and operated
• Comparing the printed prototype with components of existing systems to ensure correct fit and function

Creating a solid object for consumers to evaluate speeds the rate at which new designs can be compared. 3D-printed versions of alternative designs can be reproduced and compared much faster than individual examples of each design can be turned out, saving weeks in the production schedule.

Often, a prototype doesn’t need the material strength of the final object, so manufacturers can use a plastic or resin design to test an object before investing in the cost and materials required for final reproduction. Jewelers, for example, can test their designs in wax or biodegradable plastic at a cost of a few cents and create their final models in gold, silver, or other valuable materials after the client approves the fit and function.

3D-printed prototypes can also illustrate additional details for product evaluation by means of color and other indicators; information such as stress load or thermal measure within a structured object can be clearly represented for nontechnical review. This same capability can illustrate the visual impact of different artistic or coloring options and build marketing materials to allow early review by test audiences.

Direct digital fabrication

Creating prototypes via additive manufacturing speeds the stages of the design process, but creation doesn’t stop there. In metal fabrication systems, additive manufacturing can create final products and designs rather than just plastic prototypes. Details such as serial numbers, branded marketing designs, and even interlocking and joined structures, such as a chain or zipper, can be included in the physical structure of the product, with no tooling steps needed beyond the 3D-printed output.

Producing a single unique design (called a one-off) or another limited-production run for a specialty product, such as those used in racing, medical, and space technologies (see Figure 3-2), can be costly in traditional manufacturing. Because the same mold or tooling is used only a few times, or possibly once, no opportunities exist for efficiencies of scale that bring down per-item costs in mass manufacturing.

Direct digital manufacturing also allows updates in the middle of a production cycle without the need to retool the production line. When the digital model is modified and uploaded to the 3D printer, all future items include the change automatically. General Electric has started using this capability in the design of its future aircraft jet engines. Rapid updates keep the line in operation and save time in the production of high-precision engine components because multiple components can be combined and printed at the time. This technique doesn’t require the traditional methods of brazing and welding to combine individual assemblies.

Restoration and repair

Additive manufacturing can be used to re-create objects that have been removed from available inventory stocks to make room for new models or that have become largely obsolete.

Components such as a compressor cover for a steam-powered car or a replacement flipper for a pinball machine (see Figure 3-3) are long gone from the corner store, whether or not they were ever available to the public. (See Figure 3-4.) By scanning the broken bits of an existing design or creating a new replacement part from measurements and CAD design, additive manufacturing can bring new life to outdated designs. NASA, for example, used this technology to create new examples of the massive hand-welded Saturn V engines that once allowed humans to reach the moon.

By creating designs that can take the place of original equipment, manufacturers can improve on the originals, making the repaired item better than new. You can use new materials, add reinforcements, and make any modifications entirely within the computer before creating a part. And when you create the part in lightweight, inexpensive plastic, you can test its fit and make further adjustments before creating the final object in the desired material.

This new parts-management technique means that manufacturers no longer need to store copies of all possible parts in warehouses and other locations. Instead, they can simply download the design of the appropriate component and print its replacement when needed. Instead of waiting days or weeks for a replacement part for your car to be shipped to a local dealership, you could call the mechanic to schedule a recall item replacement, and the mechanic would print the part to have it ready when you arrive. A complete warehouse full of individual parts could be replaced by a small shop stocking only raw materials and a bank of 3D printers. No items will be out of stock, and options could include different materials for special needs or personalized designs based on standard fittings or connectors.

Household goods

Today, you might 3D-print a hammer to use to hang a photograph on your wall. The photograph itself could be 3D-printed in full color as a single object that includes a frame, as well as a cover pane of transparent plastic that gives the photo the same look and feel as a traditional framed picture. As more materials and complex assemblies are created through additive manufacturing, new products can be fabricated with the same color, shape, and function as the originals (see Figure 3-4).

As additive manufacturing technology improves in sophistication — to the point of printing complex, multiple-material objects such as integrated electronics and composite interlocking structures — the range of printable objects will expand. Eventually, you’ll be able to 3D-print many items that you commonly use around the house — and the house itself!

Buildings

Soon, much larger 3D printers that extrude concrete may fabricate complete structures, like the one shown in Figure 3-5, intact. Human contractors wouldn’t be required to assemble individual components and affix those assemblies to a foundation; the final structure would emerge from the printer.

Emergency shelters created for use after natural disasters such as hurricanes, earthquakes, and tidal waves could be replaced by solid shelters formed from natural materials present in the local environment, such as the open structural framework in Figure 3-6. This illustration is a small-scale creation formed by focusing concentrated sunlight on sand, found on beaches and in deserts around the world. The 3D printer merely moves the focal point across the sand to fuse individual granules into solid structures.

Additive manufacturing techniques also allow the creation of complex interior spaces to accommodate wiring, plumbing, and insulation. This process is quicker and more efficient than creating such spaces in traditional concrete slabs poured in wood frames. Figure 3-7 shows the creation of a corrugated concrete wall. This wall could retain its empty air pockets, or those gaps could be filled with materials such as foam or dirt to provide greater thermal protection. This process provides the same structural support capacity as traditional construction but uses far less material and doesn’t generate scraps, cutoffs, and leftover material. Eventually, even plumbing and wiring will be fabricated directly into the structure itself.

Even now, the industry is on the verge of printing homes — or entire high-rise buildings — by using 3D printers that climb up the buildings that they’re creating, lifting themselves to build one floor at a time (see Figure 3-8). This model is constructed much as the ancient Egyptians constructed the Pyramids at Giza, but such printed buildings could have complex curved walls instead of traditional stick-frame construction.

Bridges

Overseas, the Europeans are building bigger designs such as walls and bridges. A pair of robotic arms can print a full-size bridge in its intended location (visit http://mx3d.com/projects/bridge/ for more information) rather than pieces and parts to be assembled. The bridge can be completed in less time than traditional manufacturing would take. Printing a single unit also produces far fewer spare parts that would have to be sold or discarded.

Lost-material casting

3D-printed materials such as thermoplastics and extruded wax designs can be used for lost-material casting, a process that’s commonly used to create precious-metal jewelry. After the final design is created in a computer, the object can be printed with additional material to form basins, sprues, gates, and runners as a single object. This object is embedded in casting clay. When the clay has set, the cast mold is heated, allowing the plastic or wax to evacuate the casting mold cavity.

Sintered metal infusion

Manufacturers can make artistic metal objects by sintering inexpensive granular material such as steel into solid form. Because sintering doesn’t involve melting, the resulting object is a porous mesh of steel particles bound into the desired shape. The object may be quite fragile, depending on the technique used to sinter the granular material. Embedding these objects in casting clay allows the introduction of a more artistically desirable material (such as bronze) into the mold, filling the void defined by the steel granules. After polishing, the resulting metal amalgam can produce an alloy with desirable artistic or material traits. Such processes can bind materials with dissimilar properties — impossible in traditional alloy injection molding.

Medical implants

Perhaps the most specialized application of additive manufacturing is the creation of medical implants, which must fulfill a function while performing in harmony with the organic structures of the body (see Figure 3-9).

3D printing is limited only by the size of an object. Thus, the object’s interior geometry can be solid, hollow, or complex. Objects can be created quickly, with optimum balance between strength and weight and minimal materials cost and waste. Metals are often used in medical implants because they’re not reactive to the body’s natural processes. Titanium is popular but has such a high melting temperature that most designs are cast as solid models. This approach is costly for the patient and raises the possibility of postoperative damage from vibration and movement of the implant against biological materials such as bone.

Figure 3-10 shows a titanium artificial hip implant created by a 3D printer via selective laser sintering (SLS). This implant’s highly complex metal geometry allows bone to grow into the implant itself, forming a bond that’s much stronger than traditional screws and adhesives can provide.

Biological implants (organs)

3D printers can print materials other than plastic and metal, of course. Biological materials can be used to print replacement organs and tissues that can be implanted without rejection. These implants can be fabricated from the recipient’s own cells, so no rejection occurs and a perfect match is made with the patient’s unique biology.

Item personalization

Personalization isn’t restricted to material objects such as cellphone cases. A far more specialized application is biological prosthetics for reconstructive purposes or for replacement of missing limbs.

After a patient suffers massive facial injury, for example, 3D printing can re-create that person’s features from old photographs or via modeling based on remaining body elements. This technique can return the ability to eat and drink normally to people who have suffered facial injuries or diseases. It can also provide a new ear for a person born with a functional inner ear but no external ear. Researchers are using 3D bioprinters to test bioengineered ears, using collagen and living cells to form a new structure that can be implanted to restore proper function.

External prosthetics have traditionally been little more than solid forms with as much articulation as their designers could provide. For example, one company creates custom coverings, called fairings, designed by creating a 3D model from a scan of the remaining limb. By mirroring the existing limb, the design integrates artistic designs with a balanced appearance created by an artist working with the recipient. Fairings can be created in plastic, or even chromed metal, using 3D printing to create a look that fits the recipient’s unique personalized preference. (See Figure 3-11.)

Clothing and textiles

Artists are developing new materials such as 3D-printed artificial leather and flexible lattices for use in clothing and footwear fitted to the recipient’s form.

Designer Michael Schmidt and architect Francis Bitonti teamed up to create a 3D-printed gown custom-fitted to fashion model Dita von Teese, as shown in Figure 3-12. This dress was created from a curved latticework design based on the Fibonacci sequence, a mathematical relationship that defines many of nature’s most beautiful shapes. Applying the lattice to a scan of the model’s body allowed the creation of a 3D-printed mesh complete with interlocking flexible joints.

The designers added Swarovski crystals to enhance the gown’s appeal on the catwalk, but advances in multiple-material printers may make that treatment unnecessary in the near future. If this technology becomes more common, customers will step into a scanner and select the desired material to create custom-fabricated, 3D-printed pants that won’t bunch at the waist or fall down on the hips.

Military operations

The U.S. Navy operates ships for extended periods far from land, and these ships sometimes need parts or modifications that aren’t readily available. Some ships employ onboard additive manufacturing systems for prototyping modifications and fabricating components.

Eventually, additive manufacturing will allow in-place repairs of equipment that currently can’t be done outside a service yard. Metal cladding, for example, can use this process to add material to an existing metal object, allowing damaged or corroded mechanical equipment to be repaired. Submarines may be equipped with specialized 3D printers that crawl along the spaces between the inner and outer hulls, making repairs that are currently impossible.

The U.S. Army created the Mobile Expeditionary Lab, a 20-foot shipping container packed with rapid-fabrication systems that can be used by soldiers in the field who don’t have access to parts shops and metalworks. Early successes of this lab include creating new brackets to make equipment fit on local vehicles and small covers that prevent soldiers’ flashlights from being turned on accidentally during maneuvers. Bringing this capability to the location where the object is being used makes it possible to identify needs and test designs that fit the locale (a desert, say, as opposed to a jungle). Currently, the Army can get a new product, component, or update into use within days. Designs created at the lab are uploaded to a location where they can be reviewed, updated, or sent for full-scale fabrication, shortening the supply chain between the troops and their gear.

Space

Few environments provide a greater challenge than in space. If the only wrench that fits a spacecraft’s radio mast gets lost during repairs, for example, it’s exceptionally difficult to have a replacement delivered. No wonder NASA and other space-flight services are investigating additive manufacturing. Being able to make what astronauts need in flight and en route, using basic materials and a 3D printer that can work without gravity or in a vacuum, is potentially a vital feature of future spacecraft.

The cost of lifting anything off the Earth is still (pardon the expression) astronomical. For missions to other planets, the use of native materials such as lunar soil and solar energy will be very appealing. As discussed earlier in this chapter, we’re already able to use sand and dirt in additive manufacturing. If we can adapt the same systems used here on Earth so that they can be used on the moon, then we can send robotic systems ahead to print out roads and structures to house our astronauts without further cost for lifting materials to orbit and to the escape velocity beyond that. (See Figure 3-13 and Figure 3-14.)