Issue 32 – October 2011
3D printing, also known as additive manufacturing (AM) or rapid manufacturing RM) was introduced over 2 decades ago in the form of rapid prototyping (RP). As it enters mainstream manufacturing, AM signals a move from mass production to mass customisation and personalisation in the creation of many goods. It could also herald more energy-efficient and cleaner manufacturing processes, and significant changes in manufacturing.
Manufacturing, as we know it today, dates back to the late 1890s and early 1900s. It is essentially based on the mass and efficient production of large volumes of goods, resulting in economies of scale and cheaper products. Return on capital investment is a determining factor. Most modern manufacturing is still firmly anchored in this model.
Mass production is often based on subtractive manufacturing, where the production methods dictate the design of products for optimal workflow. Inputs, such as metals or plastics, are processed and shaped into oversized products through moulding, pressing, or die-casting before layers of excess material are removed by machining (drilling, trimming, and so on) or other methods to get a finished result. Modern manufacturing using computer numerical control (CNC) machine tools has greatly improved the efficiency of such 'destructive' processes, but it still produces large amounts of waste material that need recycling, and require cleaning and replacement of machining equipment.
Fresh solutions drawing on new technologies are needed to face current and future industrial and economic challenges.
From making models to manufacturing
There is a prototype behind every manufactured product. From concept to function, models are needed to define the shape, feasibility, functionality, and other parameters of a product, and to test potential customers' reactions.
The introduction of computer-aided design (CAD) in the mid-1960s, followed by computer-aided manufacturing (CAM), and their use with CNC machine tools, greatly enhanced and sped up the design and production of prototypes, and ultimately of manufacturing.
A new process for making prototypes comparatively cheaply emerged in the late 1980s. Taking data from three-dimensional CAD drawings, a machine lays down very thin coats of material, usually plastics, in powder, liquid, or resin form and hardens them to create a model rapidly, earning this technology the name of rapid prototyping. RP enabled companies to send designs of parts to their subsidiaries in different countries and continents instantly and have the parts reproduced locally, rather than having to ship them.
Within a few years rapid tooling (RT) was introduced to create moulds quickly or to fabricate tools for a limited volume of prototypes. The first RT machines were expensive but reduced the cost and time spent on making moulds, preparing tools, or finishing incomplete models.
This additive method eventually led to AM, enabling objects to be produced following the same process: adding nanometre-thick layers of various materials and using lasers to fuse them (a process also called sintering) or ultraviolet light to cure certain resins.
International Standards are central to future of AM
IEC Standards will be essential to the expansion of additive manufacturing. One area likely to expand is that of 3D printers: systems that use a wide array of electric and electronic components, including switches, relays, servo motors, ultraviolet lights, and different types of lasers. Among the many IEC Technical Committees (TCs) preparing Standards for such components is TC 76: Optical radiation safety and laser equipment. TC 76 is the leading body on laser standardisation, including for high-power lasers used in industrial and research applications, and will play an important role in AM's expansion here.
3D printing/AM opens up new perspectives in manufacturing, especially the cost-effective production of high-tech items or very complex products in relatively low volumes in a single process and not requiring long lead times. Another area lies in the costly manufacture and assembly of different parts which are often very small and made up of different materials. This is an important consideration in new technology sectors, such as aircraft or satellite production, where some parts are not needed in large volumes and have to be manufactured in complex steps.
'ATKINS: Rapid Manufacturing a Low Carbon Footprint', a Zero Emission Enterprise Feasibility Study from Loughborough University, United Kingdom, gives several examples of potential environmental and economic benefits. For instance, it is not unusual to find 15kg of expensive alloys being used to produce just 1kg of high-value aerospace components. Excess material must be recycled and waste and chemicals, such as shavings, contaminated lubricants, and slurries produced in the machining process have to be treated at substantial additional cost, consuming still more energy.
By contrast, in a single procedure and using only the raw material needed, RM can produce highly complex items. These may include latticed microstructures and variable density surfaces or cavities. When the process is complete, the part is removed, excess material that has not been sintered is cleaned and can be reused almost entirely (in the case of metal sintering) or partially (in the case of polymer sintering). The volume of waste residue is cut drastically.
Unlike conventional manufacturing, in which a multitude of machines and processes are required to cast, press, shape, trim, and polish products, AM can create a wide assortment of items from the same device when similar material is employed – machines used for metal sintering cannot process plastics, for instance. No retooling is needed between tasks, only new 3D CAD data, resulting in much shorter lead times and significant production savings.
Hi-tech quickly at relatively low-cost
Complex parts, such as a swirler (fuel injection nozzle) for gas turbines have been produced in a single manufacturing step from a cobalt chrome alloy using a direct metal laser-sintering system from Electro Optical Systems (EOS). In spite of its complexity, the 10 – 15 cm swirler was made in a single manufacturing step and did not require complicated and costly machining or the welding of some 10 separate parts, always a potential source of weak spots and cracks. Aircraft manufacturers such as Boeing or European Aeronautic Defence and Space routinely use AM to manufacture more reliable aircraft parts and drastically cut production cost and weight.
Scientists and students from Southampton University, UK, designed and made a 1.2 metre wingspan UAV (unmanned aerial vehicle) using 3D printers. Southampton University Laser Sintered Aircraft (SULSA), which has a range of 45 km and can fly at up to 140 kph, was designed in 2 days and printed in 5. This short lead time between design and manufacturing allows designers to test out new ideas and prototypes quickly. Some of the benefits mentioned by the SULSA team are complete structural freedom for the designer at no cost and where the complexity of the design has no impact on manufacturing costs, a parametric design that can be stretched or resized, and a complete separation of design and construction with 'print where you need' possibility.
AM is still a nascent technology, used mainly in high-tech or niche environments, for the low-volume production of small to medium size and complex parts, for which it is cost-effective. However, AM will find its way into mainstream manufacturing and will lead to mass production, giving way to mass customisation and on-demand production in many domains.
AM could herald another industrial revolution. Speaking to the BBC in July 2011, Neil Hopkinson, a senior lecturer in the Additive Manufacturing Research Group at Loughborough University, said that AM 'could make off-shore manufacturing half way round the world far less cost effective than doing it at home. Rather than stockpile spare parts and components in locations all over the world,' he argued, 'the designs could be costlessly stored in virtual computer warehouses, waiting to be printed locally when required.'
Evidence of the growing success of AM can be found in a May 2011 report by Wohlers Associates, an independent consulting firm on new developments and trends in additive manufacturing. Wohlers indicates that 'the compound annual revenue growth rate produced by all AM products and services was an impressive 26.2% for the industry's 23-year history'. Wohlers Associates conservatively forecasts industry-wide revenues to grow from USD 1.3 billion in 2010 to USD 3.1 billion in 2016. The report also predicts the industry will ship 15 000 3D systems a year by 2015. The relatively low and falling price of RM equipment (sales are largely driven by machines selling for between USD 5,000 and USD 25,000) means the return on large capital investments is no longer the constraint it is in traditional manufacturing.
Although 3D printers are relatively small – EOS' largest DMLS system, the EOSINT M 280, has a footprint of 2.4 m2 and weighs 1 250 kg – advanced AM machines are not yet 'just round the corner at a 3D print shop on the high street', as Hopkinson is forecasting they will be.
Summarised from IEC e-tech August/September 2011.