Versatile 3D printing broadens its appeal

Paul Boughton

3D printing, in all its different forms, is now an exceptionally versatile process, capable of creating models and actual components for a variety of diverse applications. Paul Stevens reports on some of the latest developments relating to 3D printing machines and materials.

From its early beginning, as a technique to make prototypes that could only approximate the shape and properties of the part being represented, 3D printing has come a long way. The concept - which encompasses a range of techniques - uses layering to build up complex parts. It is still used to make prototype parts but, increasingly, 3D printing is being used to make the final, fully functional components.

Industry consultancy Wohlers Associates says that sales of rapid prototyping and additive manufacturing technologies bounced back in 2010. According to Wohlers Report 2010, demand for products and services using additive-manufacturing (AM) technologies grew by an estimated 13.9 percent in 2010. In contrast, compound annual growth rate (CAGR) had slowed to 3.3 percent over the previous three years.

Nevertheless, the last 12 months has seen many interesting developments in the field of 3D printing. Terry Wohlers, the principal author of the report and president of Wohlers Associates, states: "Using AM for part production is considered the next frontier, with opportunities beyond measure. Corporations, entrepreneurs, investors and researchers are considering ways in which AM can be used to manufacture an exciting array of products in quantities of one to several thousands."

Two distinct markets are developing for products made by additive manufacturing: one is the professional market, which includes the medical, dental, aerospace, automotive and motorsports industries; the other is the consumer market, for products such as home accessories, toys and fashion accessories.

Entry-level 3D printers

Clearly the optimum 3D printer for a given application will depend on the type of application but, in terms of purchase cost, towards the bottom end of the market Z Corporation recently launched the ZPrinter 350. This machine converts 3D data into monochrome physical models in a largely automated process (Fig. 1). Using the ZPrinter 350 to create a model is said to be almost as easy as printing a document on paper using a conventional printer. Over the past year or so, other companies introducing new 3D printers for use in an office environment have included Objet Geometries with its multi-material Connex350, Stratasys with its Dimension uPrint Plus for true multi-colour, desktop 3D printing, and Solido3D with its low-cost SD300 Pro 3D printer that is said to be the only desktop 3D printer to use Laminated

Object Manufacturing (LOM) technology

While equipment has played an important part in the development of 3D printing, specialist materials have also been instrumental. For example, Huntsman's SL 7870 stereolithography (SLA) resin is claimed to offer glass-like appearance, high component strength and properties that are comparable to those available from moulded ABS (acrylonitrile-butadiene-styrene). The material is also dimensionally stable in humid environments.

Another high-performance material has been developed by 3D Systems. Its Accura Peak Plastic is an SLA material for optimal performance, accuracy and stability during prolonged exposure to elevated temperature and humidity. It is aimed at demanding applications that require high levels of strength, stiffness and thermal and humidity stability. 3D Systems says the material can be used for high-definition master patterns, fixtures and jigs, thermoforming tools and functional models requiring accuracy and dimensional stability over time. Steve Hanna, 3D Systems' director of materials sales and marketing, comments: "This is a breakthrough material tailored for extreme operating environments for our growing base of automotive, motorsports and aerospace users."

DSM Somos has recently introduced Somos Next, an SLA resin that is claimed to approach 'true thermoplastic performance.' Parts made from this material combine stiffness and toughness, but also benefit from high feature detail, dimensional accuracy and good aesthetics.

DSM Somos' marketing manager, Vince Adams, says: "This is a material you need to hold in your hand to fully appreciate. The stiffness/toughness combination produces a look and feel that is so like a thermoplastic - people are really surprised that it is actually stereolithography." Parts made from this resin can be used in functional testing applications and low-volume manufacturing applications where high toughness is required. Target markets include aerospace, automotive, consumer products and electronics. The material can also be used to make functional end-use performance prototypes including snap-fit designs, impellers, duct work, connectors and sporting goods. Adams adds: "The unique combination of mechanical properties is what gives Somos Next its key advantage compared with all previous SL resin options. We beta tested this material among a group of demanding professionals. They agree that Somos Next represents a generational step forward in producing prototyped SL parts."

New supplier

One company that is a newcomer to 3D printing is HP, which launched its HP Designjet 3D at the recent Subcon show. In fact these printers are manufactured by Stratasys and incorporate its patented Fused Deposition Modeling (FDM) technology. Stratasys chairman and chief executive officer, Scott Crump, believes the time is right for 3D printing to become mainstream. According to HP, the Designjet 3D allows designers to achieve faster time-to-market and cost savings during product development (Fig. 2). It is also claimed to set a new standard for automated 3D printing, office integration and reliability.

HP has launched two Designjet 3D printers, with prices starting around EUR13,000. The HP Designjet 3D printer creates accurate models in ivory-coloured ABS, while the HP Designjet Color 3D printer produces parts in eight colours. Santiago Morera, vice president and general manager of HP's large-format printing business, says: "The affordability of the HP Designjet 3D printers means that businesses that choose these products are likely to see a return on investment very quickly. If they are outsourcing just five to ten models per month, the printer can pay for itself in one year and, if only one error is detected before tooling, it can potentially save them thousands."

The new machines also feature the HP Designjet 3D Removal System, which removes excess model material within a normal office environment. In addition, the 3D printers produce models that are ready-to-handle without gloves, and the printing and post-processing of the models is automatic, requiring no manual finishing. Built from ABS, the models are durable and functional.

Researchers at De Montfort University (DMU) in the UK are looking to develop a machine that will produce complex plastic parts on demand, using laser printers and powder. DMU's Rapid Manufacturing and Prototyping Group is part of a £750,000 (approximately EUR900,000) project, part-funded by the UK's Technology Strategy Board, called Selective Laser Printing of High Performance Polymers (Sprint). Parts produced this way could be used in industries such as aerospace and automotive.

As well as the Technology Strategy Board, other partners include rapid manufacturing specialists MTT Technology, Renishaw and Parker. The Sprint project team intends to develop a compact, energy-efficient machine, together with a range of compatible polymer materials. The machine will precisely deposit powder using an adapted industrial laser printer before the entire layer is fused by infrared radiant heater.

Jason Jones, who leads the project, comments: "Selective laser printing has the potential to compete with conventional manufacturing techniques without the requirement for expensive moulds." DMU's Professor David Wimpenny adds: "The machine we are developing will produce parts with outstanding mechanical properties because every layer is fused using controlled heat and pressure. The process also has high processing speeds and excellent resolution."

Tutankhamun's mummy

3D printing is now an extremely versatile process, with applications far beyond the creation of parts for product development purposes. For example, Materialise, the Belgium-based rapid prototyping bureau, has recently used stereolithography to create a replica of King Tutankhamun's mummy for the Discovery Times Square exposition in New York. The operation was led by natural history and prehistoric model maker Gary Staab, of Staab Studios.

The process began by importing CT (computed tomography) scans of the Tutankhamun mummy into Materialise's Mimics software to create an exact 3D model of the mummy. From there, 3-matic software hollowed the model. Hollowing is important because it reduces the amount of material used, speeds the build and makes the final product lighter. Once the digital model was ready, the team used its Magics software to fix the file and make the model 'watertight' - which is a crucial step in 3D printing.

Materialise used one of its very large Mammoth stereolithography machines to build the model (Fig. 3). Because the build material is a liquid resin, the part must be supported as it is built; Materialise's e-Stage software automatically generates these supports, but they are easily removed afterwards during the post-processing stage (Fig. 4).

From Materialise's facility in Belgium, Tutankhamun's model was transported to the Staab studio in Missouri, where Gary Staab added detail, colour and texture to make the replica appear identical to King Tutankhamun's mummy.

While the mummy model is an extreme example of what 3D printing can achieve, companies wishing to implement 3D printing in an office or research and development environment can today take advantages of the latest generation of machines that are characterised by being faster, more user-friendly, and cheaper to buy and run, with the resultant models being robust and durable (Fig. 5). In many cases, the machines' resolution can challenge that offered by rapid prototyping and manufacturing machines that, not long ago, were considered to be the state of the art. Indeed, today the boundaries between 'office' 3D printing and these other 'high-end' technologies are now becoming blurred. Furthermore, the ability to print with multiple materials offers users significant functional and aesthetic advantages.

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