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Product Disassembly Studies
CHAPTER
Product Disassembly Studies
2
CHAPTER OUTLINE 2.1 2.2 2.3 2.4 2.5
Introduction ...................................................................................................................................11 Outdoor Design: Bus Shelters ..........................................................................................................12 Indoor Design: Domestic Extraction Hood .........................................................................................15 Product Disassembly Studies ..........................................................................................................18 Further Reading ..............................................................................................................................19
2.1 INTRODUCTION This book aims to familiarize you with the main manufacturing processes, as well as their possible applications in all sorts of products. This require a hands-on approach, whereby you actively study the products you encounter in everyday life and ask yourself how they are made. Indeed, most chapters begin with an exercise designed to stimulate you to do precisely this: for instance, Chapter 3 on casting of metals asks you to identify several cast parts and products right from the start. It might be tempting to limit yourself to an image search on the Internet, or even to skip those exercises altogether, but that would be a mistake. It is important to have such products at hand, so you can not only see them from a distance and at just one angle, but look at them closely, from all angles, and literally get a feel for the component. This way, many of the theoretical and practical concepts covered in this book will come much more alive. This chapter is intended to help you make these instructive explorations. Section 2.4 introduces you to product disassembly studies, which basically involve taking products apart, considering how their various components are made, and finding out how they have been assembled together. If you are technically inclined (which every student of design and engineering must be to some extent: otherwise, why choose such studies?), you have probably already taken apart quite a few products during your lifetime, and you can now learn how to take this hobby to the next level. One quick warning: always consider safety, and never put yourself, or others, at risk. Before setting you off on disassembly of products, we show a few exemplars of everyday products and discuss how they were made. As you will see, nearly all of the manufacturing processes covered in Chapters 3 to 12 are encountered in these sample products. Of course, many more could have been included, but because this book aims to be selective, we limit ourselves to just two products: one outdoor application and one typical indoor product, both examples of industrial design.
Manufacturing and Design Copyright © 2014 Elsevier Ltd. All rights reserved.
11
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CHAPTER 2 Product Disassembly Studies
EXERCISE 2.1 Find a product that is ready for recycling or disposal—for example, an old vacuum cleaner, coffee machine, or computer, or perhaps something bigger such as a lawnmower (preferably products that contain mainly metals and/or plastics). Save it for Section 2.4!
2.2 OUTDOOR DESIGN: BUS SHELTERS Bus shelters come in all sorts and sizes. Over the past decades, their design and manufacture has developed to a degree of sophistication that may be surprising at first, but that becomes readily apparent to anyone who gives these objects a closer look—and considering that if you use them you inevitably spend some time in them, we suggest you do so. Here, we present a bus shelter known as “De Gouwe,” designed for various municipalities and provinces in the Benelux region. It is currently manufactured by the company Epsilon Signs in Bree, Belgium, with placement and maintenance done by the company OFN in Buren, The Netherlands. Fabrique Public Design in Delft, The Netherlands, was responsible for its design. All information and illustrations in this section are courtesy of this design bureau, which has been active in bus shelter design since 1993. Figure 2.1 shows an exploded view of one version of De Gouwe with its main components and how it looks in the street. Since its introduction into the market in 2009, more than 4,000 of these shelters have
FIGURE 2.1 Exploded view of the “De Gouwe” bus shelter. (Inset: the “De Gouwe” in real life.) (Images courtesy of Fabrique Public Design, Delft, NL)
2.2 Outdoor Design: Bus Shelters
13
been installed in the Benelux countries, in various versions and color schemes. Manufacturing this shelter involves a variety of processes: aluminum extrusion (support poles, roof frame, various smaller parts), metal casting (various parts of the bench and garbage bin), concrete casting (base plate, with inserts for easy assembly of the other components), and sheet metal forming (roof plates, various parts of bench and bin). It also involves a fair number of standard components that are bought in, such as glass panels and lighting elements. Assembly relies on screws, bolts, and other mechanical fasteners; welding (for the roof frame profiles); and clamping. Finishing involves powder coating (for sheet metal parts, certain extrusions) and anodizing (all other extrusions). In total, the De Gouwe shelter contains 729 parts, 168 of which are uniquely designed and manufactured for this shelter—that is, product-specific parts (of which 12 are custom-made fasteners). In total, it contains 575 fasteners. Some noteworthy details are as follows: •
•
•
All metal castings are made from aluminum using the sand casting method. This requires a modest investment for the casting molds. The method offers a large form freedom and is well suited for the relatively modest production volumes involved (Chapter 3). The castings are cleaned after manufacture and receive a double layer of powder coating (Chapter 13). Like the castings, all extrusions are also made specifically for this shelter. This requires some investment for the extrusion dies, but the benefit is that extrusion allows integration of all kinds of assembly functions into the extruded profile (Chapter 5); Figure 2.2 provides an example. The extrusions are either anodized or powder coated to get the right “look and feel” as well as corrosion resistance (Chapter 13). The sheet metal roof panels are made from galvanized low carbon steel. They are made by first cutting, or “blanking,” the input sheet material into the right cutout shape, then bending its four edges, and finally powder coating. All of this can be done using universal equipment, so no investments are needed for these parts (Chapter 4).
The shelter involves three major sub-assemblies: the advertising box, the bench, and the garbage bin; the latter is shown in Figure 2.3. Note how it combines castings, extrusions, and sheet metal parts. The side panels are decorative only and, like the shelter’s roof frame, can be powder coated in any color as desired. Such combinations of processes are in fact common, with complex parts being cast in metal or molded in plastic, less complex profiles being extruded or roll formed, and simpler parts being made by sheet metal forming or plastic thermoforming.
FIGURE 2.2 Cross section of extruded rear-right side profile, with integrated glass panes and fasteners. (Image courtesy of Fabrique Public Design, Delft, NL)
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FIGURE 2.3 Exploded view of garbage bin, with cast concrete foot. (Image courtesy of Fabrique Public Design, Delft, NL)
As a bus shelter, the De Gouwe is very successful, thanks to a number of key design decisions. First, it has a modular design, which allows a range of shapes, sizes, and color schemes with the same set of basic components. This modularity also allows fast assembly indoors, with a total assembly time of under four hours per shelter by a crew of one. Once assembled, the shelter is ready for placement in the street. Connecting it to the power network can be time consuming, but with an optional PV module and battery to provide electricity for lighting, the shelter becomes fully self-sufficient and can be placed in under 10 minutes. Furthermore, its minimalist design is not only aesthetically pleasing but minimizes the accumulation of street dirt and facilitates maintenance, which in turn keeps operating costs low. Of course, it is not vandal-proof, but cracked windows and other damage can be quickly and efficiently repaired. In fact, with the revenue from the advertisements in its poster frame, the shelter can actually bring in money. Durability helps, too: the design life span is 20 years, thanks to corrosion- and wear-resistant materials. Finally, costs have been reduced not only by the modular design but also by careful optimization of all parts, pushing the manufacturing technology to the limits without impairing quality. For instance, the wall thickness of all extrusions has been minimized, saving weight and, hence, costs. Of course, despite its success, De Gouwe represents only one approach out of many possibilities, and several contemporary alternatives can be found, such as using steel for the main structure instead of extruded aluminum, or using a wooden bench instead of a metal one. The perfect bus shelter simply does not exist. But De Gouwe illustrates very well how various manufacturing processes can be successfully combined. Take a good look at a bus shelter, next time you find yourself in one, and try to see how it was made and which materials and processes were used!
2.3 Indoor Design: Domestic Extraction Hood
15
2.3 INDOOR DESIGN: DOMESTIC EXTRACTION HOOD In most domestic kitchens, you will find an extraction hood mounted on the wall above the stove, placed there to remove fumes generated during cooking. These hoods are usually made of steel and glass, and consequently they are mostly shaped like a flat box: the materials in question do not lend themselves well to more complex shapes, unless used for products made in large numbers, such as cars (more on this in Chapter 4). Installing these hoods is often a challenge, as they are heavy and usually require a tube connection through the kitchen wall or roof to the outside environment. Furthermore, changing the filter requires some time and skill and is therefore often done too late, causing smells to linger in the kitchen. Working for the German kitchen appliances manufacturer Gutmann, the Dutch design bureau Van Berlo came up with an innovative solution. The hood design, shown in Figure 2.4, uses a fan-driven cyclone process to clean the air. Basically, dirty air rising from the stove is sucked into the hood and swirled around at high speed, flinging all vapors and fume particles against the collector vanes. The air is cleaned so well that it can be recirculated into the kitchen, so no connection to the outside air is needed (recirculation also saves energy, as no hot air is blown outside in winter). Thanks to this simpler design, a low overall weight of just under 10 kg, and several smart assembly solutions integrated into the design, the new hood can be installed in well under 10 minutes. The collector itself is easy to remove and can be cleaned quickly, either by hand or by putting it into a regular dishwasher. The product’s overall shape is innovative as well: gently rounded, with a smooth, high-tech look and feel, without a single visible screw. Finally, as for price, the L’Original extraction hood, as it has come to be named, can easily compete against models from the leading brands in the kitchen appliance market.
FIGURE 2.4 Exploded view of L’Original extraction hood (left), and finished product (right). (Image courtesy of Van Berlo, Delft, NL)
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CHAPTER 2 Product Disassembly Studies
This striking and innovative design is possible thanks to a process that plays a vital role in the manufacture of countless products: plastic injection molding. In this process, further detailed in Chapter 8, molten plastic is forced into a metal mold at high pressure and rapidly cooled to shape the final part. The investment for the molds is considerable and the process is therefore only suited for larger production volumes (e.g., at least 10,000/year), but on the positive side, the freedom in forms, details, and materials is huge. This allows double-curved shapes to be made with optimized strength and stiffness, at low weight. Injection molding also enables the designer to integrate all kinds of functionality into parts, such as snap-fit joints and cable guides to allow fast assembly, thereby saving costs. Painting or finishing is not necessary; indeed, the process enables the manufacturer to quickly change the part color by selecting a differently colored plastic. In total, the L’Original hood contains 124 individual parts, including 59 fasteners (screws, clips, etc.) and 22 product-specific parts, 19 of which are made by injection molding. Some noteworthy manufacturing details include the following: •
•
•
For the overall product architecture, Van Berlo separated the structural parts, which carry all forces and act as an assembly base for all other components, from the non-structural, external covers. This allowed the company to select glass-filled nylon (PA66) for the structure, which is strong and stiff but not very attractive to look at, and an unfilled, good-looking ABS for the covers. The joints between the front and side covers were not made with conventional snap-fits, as these inevitably give rise to unsightly “sink marks” on the surface (see Chapter 8 for details). Also, as the higher temperatures above a stove may lead to material relaxation, loosening of snap-fits was a potential risk. Instead, a solution was found using two tiny aluminum extrusions, which simply slide over two rows of hooks on the two parts to be joined, as shown in Figure 2.5. Safety considerations demand that the 44 W motor and fan cannot be accessed while the motor is running. This was made possible by timer actuators that release the bottom mesh plate only when the motor has stopped turning. Also, trip switches have been integrated into the structure precisely where the mesh plate is clicked into place. Because there is no plate and no current, safety is assured (Figure 2.6).
Development of the L’Original extraction hood took roughly 1.5 years from first idea to market introduction at the Living Kitchen industry fair in Cologne, Germany, in January 2013. Up to that point, a significant development budget had been invested to make this product a reality. And with good reason: the hood immediately attracted much attention thanks to its striking design, ease of installation, improved usability and performance, low power consumption, and high filter efficiency. Currently it looks likely that the target production figures of some 50,000 units per year for a five-year production run will be easily reached. As with the bus shelter, there is no perfect design for an extraction hood, and the L’Original is no exception. Market requirements are simply too varied to allow a single product to meet all demands, for all occasions. But the new hood does represent a radical departure from the traditional shape and operation of such products (and of manufacture: consequently, the steel-oriented Gutmann company also needed some time to adapt to the new materials and processes). This begs the question: which other household products that today are still steel-dominated could literally change shape using plastic injection molding? Of course, many products—vacuum cleaners, steam irons, hair dryers—have already made this switch, but not all of them. Take a good look around your house one day, and consider how manufacturing has not only shaped the way things look, but also how they can one day be transformed.
2.3 Indoor Design: Domestic Extraction Hood
17
FIGURE 2.5 Detail of fairing joint with extruded rail (top view). (Image courtesy of Van Berlo, Delft, NL)
FIGURE 2.6 Detail of mesh plate joint with integrated trip switch (bottom view). (Image courtesy of Van Berlo, Delft, NL)
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CHAPTER 2 Product Disassembly Studies
2.4 PRODUCT DISASSEMBLY STUDIES In Exercise 2.1 you were asked to select a product that is ready for recycling or disposal. We now suggest that you disassemble this product, study its parts and components, and complete the exercises that follow. This is not only the ideal preparation for working your way through this book, but it is also an important part of what professional designers do—after all, why design everything new from the ground up when you can learn from existing products, thereby saving valuable development time? (Conducting detailed part and material audits for a product is also a key part of life cycle analysis to assess the environmental impact of products; disassembly studies, as shown in Chapter 14, also play a role in recycling.) Don’t be fussy: since the product does not need to be re-assembled afterward, it is fine to cut through parts of your product to gain access to underlying components, use a power drill to destroy screws or rivets, and so on. But whatever you do, always think about your safety and that of any bystanders first: for instance, never disassemble a product that is plugged in or could be inadvertently powered up. In general, we urge you: be sensible, be safe!
EXERCISE 2.2 How many individual parts did you encounter, including all screws, clips, and other fasteners? Is this more than you expected? Did you sometimes find ambiguity in defining what was a single part and what was actually a collection of parts joined together (i.e., a sub-assembly)?
EXERCISE 2.3 Which parts are product-specific, meaning that they were specifically designed for this product? Conversely, which parts are bought in as standard components and are not product-specific?
For this next exercise, note that product-specific parts can be sub-divided into two categories. The first of these consists of all parts that require dedicated investments, such as the castings and extrusions in the bus shelter discussed in Section 2.2 The second category comprises all parts that require no investments but that do require specific operations to give them the proper shape, dimensions, and look and feel, such as the shelter’s sheet metal roof plates. Non-product-specific (or standard) parts are items such as screws and other fasteners, but also parts such as bearings, bushings, electric motors, LEDs, and other mass-manufactured items. In nearly all everyday products, these standard parts outnumber the product-specific parts by far, but the product-specific parts are the ones that literally give shape to the product.
EXERCISE 2.4 Select three product-specific parts. Which materials are used? How can you tell?
2.5 Further Reading
19
As for materials, the first and obvious distinction to make is among the four main categories of metals, plastics, ceramics/glasses, and hybrids. Next, we can distinguish among different kinds— for metals: plain carbon steel, stainless steel, wrought or cast aluminum, and so on; for plastics: polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyamides (PA), polycarbonate (PC), and the like. (Note that especially with plastics, you will often encounter trade names, such as “nylon” for PA or “Lexan” for PC.) More detailed identification of specific alloys, or plastic grades, will usually require specialist knowledge and equipment. But simple experiments can help distinguish between materials that can look similar, such as zinc and aluminum—for example, you could try measuring the density of a component by using a principle known since Archimedes’ times. To identify metals, it is essential to know that plain carbon steel—the most commonly used metal, thanks to its low cost, good strength, and excellent formability as sheet metal—is nearly always coated for corrosion resistance, with paint, zinc-, chrome- or tin-plate, or a polymer coating. In other words, what may at first sight look like stainless steel is often the considerably cheaper chrome-plated carbon steel. (How can you tell the difference? Austenitic stainless steel is not magnetic, whereas carbon steel is—a huge benefit in sorting mixed metal scrap for recycling.) To identify plastics, a good hint is that in contemporary products, the type of plastic is often designated on the part (e.g., “PP” for polypropylene or “PC” for polycarbonate) or, alternatively, via a number code within a triangular recycling symbol (1 for PET, 2 for HDPE, and so on). (It is not always this easy: in one product disassembly case study, the designation “AS” on a plastic part turned out to be short for “anti-static,” not for some kind of polymer.) And a final tip: if you have access to the Cambridge Engineering Selector (CES) EduPack, note that this database also includes typical applications of each material it contains, and these applications are searchable.
EXERCISE 2.5 For the same three parts, which manufacturing principle (e.g., casting of metals, injection molding of plastics) has been used? What design features or evidence on the product suggest your choice of process?
Unless you have considerable prior knowledge of manufacturing, this last question is, of course, not easy to answer. However, it will become steadily clearer as you work through the book; you will come to recognize why a certain process has been chosen for a certain part and how this choice has influenced both the final material choice and the part’s precise shape.
2.5 Further Reading Another bus shelter design by Fabrique, made for the city of Amsterdam and JCDecaux, was featured in a Discovery Channel episode of How do they do it? (first aired in February 2013). For a video of how the L’Original extraction hood was designed, see www.youtube.com/watch?v¼39wRbgY2I70.
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CHAPTER 2 Product Disassembly Studies
For more examples of exploring the design of everyday products, including exploded views, we recommend the following references: Ashby, M.F., 2011. Material Selection in Mechanical Design, fourth ed. Butterworth-Heinemann, Oxford, UK. (An accessible design-led text covering the selection methodology behind the CES software, but starting with an interesting take on the way that products have evolved to exploit new materials.) Industrial Designers Society of America, 2001. Design Secrets: Products—50 Real-Life Projects Uncovered. Rockport Publishers, Minneapolis, United States. (An excellent book showing how products are designed, with considerable attention to materials and manufacture.) www.ifixit.com. (This do-it-yourself repair site routinely takes apart the latest products, with a certain focus on electronics. Highly recommended!) www.toddmclellan.com. (A one-man venture, but what an effort: this Canadian photographer turns product disassembly into an art form.)
Product Disassembly Studies
2
CHAPTER OUTLINE 2.1 2.2 2.3 2.4 2.5
Introduction ...................................................................................................................................11 Outdoor Design: Bus Shelters ..........................................................................................................12 Indoor Design: Domestic Extraction Hood .........................................................................................15 Product Disassembly Studies ..........................................................................................................18 Further Reading ..............................................................................................................................19
2.1 INTRODUCTION This book aims to familiarize you with the main manufacturing processes, as well as their possible applications in all sorts of products. This require a hands-on approach, whereby you actively study the products you encounter in everyday life and ask yourself how they are made. Indeed, most chapters begin with an exercise designed to stimulate you to do precisely this: for instance, Chapter 3 on casting of metals asks you to identify several cast parts and products right from the start. It might be tempting to limit yourself to an image search on the Internet, or even to skip those exercises altogether, but that would be a mistake. It is important to have such products at hand, so you can not only see them from a distance and at just one angle, but look at them closely, from all angles, and literally get a feel for the component. This way, many of the theoretical and practical concepts covered in this book will come much more alive. This chapter is intended to help you make these instructive explorations. Section 2.4 introduces you to product disassembly studies, which basically involve taking products apart, considering how their various components are made, and finding out how they have been assembled together. If you are technically inclined (which every student of design and engineering must be to some extent: otherwise, why choose such studies?), you have probably already taken apart quite a few products during your lifetime, and you can now learn how to take this hobby to the next level. One quick warning: always consider safety, and never put yourself, or others, at risk. Before setting you off on disassembly of products, we show a few exemplars of everyday products and discuss how they were made. As you will see, nearly all of the manufacturing processes covered in Chapters 3 to 12 are encountered in these sample products. Of course, many more could have been included, but because this book aims to be selective, we limit ourselves to just two products: one outdoor application and one typical indoor product, both examples of industrial design.
Manufacturing and Design Copyright © 2014 Elsevier Ltd. All rights reserved.
11
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CHAPTER 2 Product Disassembly Studies
EXERCISE 2.1 Find a product that is ready for recycling or disposal—for example, an old vacuum cleaner, coffee machine, or computer, or perhaps something bigger such as a lawnmower (preferably products that contain mainly metals and/or plastics). Save it for Section 2.4!
2.2 OUTDOOR DESIGN: BUS SHELTERS Bus shelters come in all sorts and sizes. Over the past decades, their design and manufacture has developed to a degree of sophistication that may be surprising at first, but that becomes readily apparent to anyone who gives these objects a closer look—and considering that if you use them you inevitably spend some time in them, we suggest you do so. Here, we present a bus shelter known as “De Gouwe,” designed for various municipalities and provinces in the Benelux region. It is currently manufactured by the company Epsilon Signs in Bree, Belgium, with placement and maintenance done by the company OFN in Buren, The Netherlands. Fabrique Public Design in Delft, The Netherlands, was responsible for its design. All information and illustrations in this section are courtesy of this design bureau, which has been active in bus shelter design since 1993. Figure 2.1 shows an exploded view of one version of De Gouwe with its main components and how it looks in the street. Since its introduction into the market in 2009, more than 4,000 of these shelters have
FIGURE 2.1 Exploded view of the “De Gouwe” bus shelter. (Inset: the “De Gouwe” in real life.) (Images courtesy of Fabrique Public Design, Delft, NL)
2.2 Outdoor Design: Bus Shelters
13
been installed in the Benelux countries, in various versions and color schemes. Manufacturing this shelter involves a variety of processes: aluminum extrusion (support poles, roof frame, various smaller parts), metal casting (various parts of the bench and garbage bin), concrete casting (base plate, with inserts for easy assembly of the other components), and sheet metal forming (roof plates, various parts of bench and bin). It also involves a fair number of standard components that are bought in, such as glass panels and lighting elements. Assembly relies on screws, bolts, and other mechanical fasteners; welding (for the roof frame profiles); and clamping. Finishing involves powder coating (for sheet metal parts, certain extrusions) and anodizing (all other extrusions). In total, the De Gouwe shelter contains 729 parts, 168 of which are uniquely designed and manufactured for this shelter—that is, product-specific parts (of which 12 are custom-made fasteners). In total, it contains 575 fasteners. Some noteworthy details are as follows: •
•
•
All metal castings are made from aluminum using the sand casting method. This requires a modest investment for the casting molds. The method offers a large form freedom and is well suited for the relatively modest production volumes involved (Chapter 3). The castings are cleaned after manufacture and receive a double layer of powder coating (Chapter 13). Like the castings, all extrusions are also made specifically for this shelter. This requires some investment for the extrusion dies, but the benefit is that extrusion allows integration of all kinds of assembly functions into the extruded profile (Chapter 5); Figure 2.2 provides an example. The extrusions are either anodized or powder coated to get the right “look and feel” as well as corrosion resistance (Chapter 13). The sheet metal roof panels are made from galvanized low carbon steel. They are made by first cutting, or “blanking,” the input sheet material into the right cutout shape, then bending its four edges, and finally powder coating. All of this can be done using universal equipment, so no investments are needed for these parts (Chapter 4).
The shelter involves three major sub-assemblies: the advertising box, the bench, and the garbage bin; the latter is shown in Figure 2.3. Note how it combines castings, extrusions, and sheet metal parts. The side panels are decorative only and, like the shelter’s roof frame, can be powder coated in any color as desired. Such combinations of processes are in fact common, with complex parts being cast in metal or molded in plastic, less complex profiles being extruded or roll formed, and simpler parts being made by sheet metal forming or plastic thermoforming.
FIGURE 2.2 Cross section of extruded rear-right side profile, with integrated glass panes and fasteners. (Image courtesy of Fabrique Public Design, Delft, NL)
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CHAPTER 2 Product Disassembly Studies
FIGURE 2.3 Exploded view of garbage bin, with cast concrete foot. (Image courtesy of Fabrique Public Design, Delft, NL)
As a bus shelter, the De Gouwe is very successful, thanks to a number of key design decisions. First, it has a modular design, which allows a range of shapes, sizes, and color schemes with the same set of basic components. This modularity also allows fast assembly indoors, with a total assembly time of under four hours per shelter by a crew of one. Once assembled, the shelter is ready for placement in the street. Connecting it to the power network can be time consuming, but with an optional PV module and battery to provide electricity for lighting, the shelter becomes fully self-sufficient and can be placed in under 10 minutes. Furthermore, its minimalist design is not only aesthetically pleasing but minimizes the accumulation of street dirt and facilitates maintenance, which in turn keeps operating costs low. Of course, it is not vandal-proof, but cracked windows and other damage can be quickly and efficiently repaired. In fact, with the revenue from the advertisements in its poster frame, the shelter can actually bring in money. Durability helps, too: the design life span is 20 years, thanks to corrosion- and wear-resistant materials. Finally, costs have been reduced not only by the modular design but also by careful optimization of all parts, pushing the manufacturing technology to the limits without impairing quality. For instance, the wall thickness of all extrusions has been minimized, saving weight and, hence, costs. Of course, despite its success, De Gouwe represents only one approach out of many possibilities, and several contemporary alternatives can be found, such as using steel for the main structure instead of extruded aluminum, or using a wooden bench instead of a metal one. The perfect bus shelter simply does not exist. But De Gouwe illustrates very well how various manufacturing processes can be successfully combined. Take a good look at a bus shelter, next time you find yourself in one, and try to see how it was made and which materials and processes were used!
2.3 Indoor Design: Domestic Extraction Hood
15
2.3 INDOOR DESIGN: DOMESTIC EXTRACTION HOOD In most domestic kitchens, you will find an extraction hood mounted on the wall above the stove, placed there to remove fumes generated during cooking. These hoods are usually made of steel and glass, and consequently they are mostly shaped like a flat box: the materials in question do not lend themselves well to more complex shapes, unless used for products made in large numbers, such as cars (more on this in Chapter 4). Installing these hoods is often a challenge, as they are heavy and usually require a tube connection through the kitchen wall or roof to the outside environment. Furthermore, changing the filter requires some time and skill and is therefore often done too late, causing smells to linger in the kitchen. Working for the German kitchen appliances manufacturer Gutmann, the Dutch design bureau Van Berlo came up with an innovative solution. The hood design, shown in Figure 2.4, uses a fan-driven cyclone process to clean the air. Basically, dirty air rising from the stove is sucked into the hood and swirled around at high speed, flinging all vapors and fume particles against the collector vanes. The air is cleaned so well that it can be recirculated into the kitchen, so no connection to the outside air is needed (recirculation also saves energy, as no hot air is blown outside in winter). Thanks to this simpler design, a low overall weight of just under 10 kg, and several smart assembly solutions integrated into the design, the new hood can be installed in well under 10 minutes. The collector itself is easy to remove and can be cleaned quickly, either by hand or by putting it into a regular dishwasher. The product’s overall shape is innovative as well: gently rounded, with a smooth, high-tech look and feel, without a single visible screw. Finally, as for price, the L’Original extraction hood, as it has come to be named, can easily compete against models from the leading brands in the kitchen appliance market.
FIGURE 2.4 Exploded view of L’Original extraction hood (left), and finished product (right). (Image courtesy of Van Berlo, Delft, NL)
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CHAPTER 2 Product Disassembly Studies
This striking and innovative design is possible thanks to a process that plays a vital role in the manufacture of countless products: plastic injection molding. In this process, further detailed in Chapter 8, molten plastic is forced into a metal mold at high pressure and rapidly cooled to shape the final part. The investment for the molds is considerable and the process is therefore only suited for larger production volumes (e.g., at least 10,000/year), but on the positive side, the freedom in forms, details, and materials is huge. This allows double-curved shapes to be made with optimized strength and stiffness, at low weight. Injection molding also enables the designer to integrate all kinds of functionality into parts, such as snap-fit joints and cable guides to allow fast assembly, thereby saving costs. Painting or finishing is not necessary; indeed, the process enables the manufacturer to quickly change the part color by selecting a differently colored plastic. In total, the L’Original hood contains 124 individual parts, including 59 fasteners (screws, clips, etc.) and 22 product-specific parts, 19 of which are made by injection molding. Some noteworthy manufacturing details include the following: •
•
•
For the overall product architecture, Van Berlo separated the structural parts, which carry all forces and act as an assembly base for all other components, from the non-structural, external covers. This allowed the company to select glass-filled nylon (PA66) for the structure, which is strong and stiff but not very attractive to look at, and an unfilled, good-looking ABS for the covers. The joints between the front and side covers were not made with conventional snap-fits, as these inevitably give rise to unsightly “sink marks” on the surface (see Chapter 8 for details). Also, as the higher temperatures above a stove may lead to material relaxation, loosening of snap-fits was a potential risk. Instead, a solution was found using two tiny aluminum extrusions, which simply slide over two rows of hooks on the two parts to be joined, as shown in Figure 2.5. Safety considerations demand that the 44 W motor and fan cannot be accessed while the motor is running. This was made possible by timer actuators that release the bottom mesh plate only when the motor has stopped turning. Also, trip switches have been integrated into the structure precisely where the mesh plate is clicked into place. Because there is no plate and no current, safety is assured (Figure 2.6).
Development of the L’Original extraction hood took roughly 1.5 years from first idea to market introduction at the Living Kitchen industry fair in Cologne, Germany, in January 2013. Up to that point, a significant development budget had been invested to make this product a reality. And with good reason: the hood immediately attracted much attention thanks to its striking design, ease of installation, improved usability and performance, low power consumption, and high filter efficiency. Currently it looks likely that the target production figures of some 50,000 units per year for a five-year production run will be easily reached. As with the bus shelter, there is no perfect design for an extraction hood, and the L’Original is no exception. Market requirements are simply too varied to allow a single product to meet all demands, for all occasions. But the new hood does represent a radical departure from the traditional shape and operation of such products (and of manufacture: consequently, the steel-oriented Gutmann company also needed some time to adapt to the new materials and processes). This begs the question: which other household products that today are still steel-dominated could literally change shape using plastic injection molding? Of course, many products—vacuum cleaners, steam irons, hair dryers—have already made this switch, but not all of them. Take a good look around your house one day, and consider how manufacturing has not only shaped the way things look, but also how they can one day be transformed.
2.3 Indoor Design: Domestic Extraction Hood
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FIGURE 2.5 Detail of fairing joint with extruded rail (top view). (Image courtesy of Van Berlo, Delft, NL)
FIGURE 2.6 Detail of mesh plate joint with integrated trip switch (bottom view). (Image courtesy of Van Berlo, Delft, NL)
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CHAPTER 2 Product Disassembly Studies
2.4 PRODUCT DISASSEMBLY STUDIES In Exercise 2.1 you were asked to select a product that is ready for recycling or disposal. We now suggest that you disassemble this product, study its parts and components, and complete the exercises that follow. This is not only the ideal preparation for working your way through this book, but it is also an important part of what professional designers do—after all, why design everything new from the ground up when you can learn from existing products, thereby saving valuable development time? (Conducting detailed part and material audits for a product is also a key part of life cycle analysis to assess the environmental impact of products; disassembly studies, as shown in Chapter 14, also play a role in recycling.) Don’t be fussy: since the product does not need to be re-assembled afterward, it is fine to cut through parts of your product to gain access to underlying components, use a power drill to destroy screws or rivets, and so on. But whatever you do, always think about your safety and that of any bystanders first: for instance, never disassemble a product that is plugged in or could be inadvertently powered up. In general, we urge you: be sensible, be safe!
EXERCISE 2.2 How many individual parts did you encounter, including all screws, clips, and other fasteners? Is this more than you expected? Did you sometimes find ambiguity in defining what was a single part and what was actually a collection of parts joined together (i.e., a sub-assembly)?
EXERCISE 2.3 Which parts are product-specific, meaning that they were specifically designed for this product? Conversely, which parts are bought in as standard components and are not product-specific?
For this next exercise, note that product-specific parts can be sub-divided into two categories. The first of these consists of all parts that require dedicated investments, such as the castings and extrusions in the bus shelter discussed in Section 2.2 The second category comprises all parts that require no investments but that do require specific operations to give them the proper shape, dimensions, and look and feel, such as the shelter’s sheet metal roof plates. Non-product-specific (or standard) parts are items such as screws and other fasteners, but also parts such as bearings, bushings, electric motors, LEDs, and other mass-manufactured items. In nearly all everyday products, these standard parts outnumber the product-specific parts by far, but the product-specific parts are the ones that literally give shape to the product.
EXERCISE 2.4 Select three product-specific parts. Which materials are used? How can you tell?
2.5 Further Reading
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As for materials, the first and obvious distinction to make is among the four main categories of metals, plastics, ceramics/glasses, and hybrids. Next, we can distinguish among different kinds— for metals: plain carbon steel, stainless steel, wrought or cast aluminum, and so on; for plastics: polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyamides (PA), polycarbonate (PC), and the like. (Note that especially with plastics, you will often encounter trade names, such as “nylon” for PA or “Lexan” for PC.) More detailed identification of specific alloys, or plastic grades, will usually require specialist knowledge and equipment. But simple experiments can help distinguish between materials that can look similar, such as zinc and aluminum—for example, you could try measuring the density of a component by using a principle known since Archimedes’ times. To identify metals, it is essential to know that plain carbon steel—the most commonly used metal, thanks to its low cost, good strength, and excellent formability as sheet metal—is nearly always coated for corrosion resistance, with paint, zinc-, chrome- or tin-plate, or a polymer coating. In other words, what may at first sight look like stainless steel is often the considerably cheaper chrome-plated carbon steel. (How can you tell the difference? Austenitic stainless steel is not magnetic, whereas carbon steel is—a huge benefit in sorting mixed metal scrap for recycling.) To identify plastics, a good hint is that in contemporary products, the type of plastic is often designated on the part (e.g., “PP” for polypropylene or “PC” for polycarbonate) or, alternatively, via a number code within a triangular recycling symbol (1 for PET, 2 for HDPE, and so on). (It is not always this easy: in one product disassembly case study, the designation “AS” on a plastic part turned out to be short for “anti-static,” not for some kind of polymer.) And a final tip: if you have access to the Cambridge Engineering Selector (CES) EduPack, note that this database also includes typical applications of each material it contains, and these applications are searchable.
EXERCISE 2.5 For the same three parts, which manufacturing principle (e.g., casting of metals, injection molding of plastics) has been used? What design features or evidence on the product suggest your choice of process?
Unless you have considerable prior knowledge of manufacturing, this last question is, of course, not easy to answer. However, it will become steadily clearer as you work through the book; you will come to recognize why a certain process has been chosen for a certain part and how this choice has influenced both the final material choice and the part’s precise shape.
2.5 Further Reading Another bus shelter design by Fabrique, made for the city of Amsterdam and JCDecaux, was featured in a Discovery Channel episode of How do they do it? (first aired in February 2013). For a video of how the L’Original extraction hood was designed, see www.youtube.com/watch?v¼39wRbgY2I70.
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CHAPTER 2 Product Disassembly Studies
For more examples of exploring the design of everyday products, including exploded views, we recommend the following references: Ashby, M.F., 2011. Material Selection in Mechanical Design, fourth ed. Butterworth-Heinemann, Oxford, UK. (An accessible design-led text covering the selection methodology behind the CES software, but starting with an interesting take on the way that products have evolved to exploit new materials.) Industrial Designers Society of America, 2001. Design Secrets: Products—50 Real-Life Projects Uncovered. Rockport Publishers, Minneapolis, United States. (An excellent book showing how products are designed, with considerable attention to materials and manufacture.) www.ifixit.com. (This do-it-yourself repair site routinely takes apart the latest products, with a certain focus on electronics. Highly recommended!) www.toddmclellan.com. (A one-man venture, but what an effort: this Canadian photographer turns product disassembly into an art form.)