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Posted: February 21, 2008
Nanotechnology makes a big difference to rapid prototyping and manufacturing
(Nanowerk News) Leading suppliers of materials for rapid prototyping and rapid manufacturing are finding that nanoparticles can dramatically alter the properties of finished components. Paul Stevens looks at what is available on the market and how another nanotechnology-based process is enhancing the properties of parts built from standard materials.
Nanotechnology is now finding applications in numerous consumer products, ranging from sunscreen and cosmetics to sporting goods and guitar strings. In the field of rapid prototyping and rapid manufacturing, nanotechnology is also now offering advantages to new product development teams.
In this article we will look at materials for tooling and model building, as well as an innovative technology that improves the performance of standard materials used for rapid prototyping and rapid manufacturing.
Heavily filled with non-crystalline nanoparticles, Nanotool resin is one of the Protocomposite materials available from DSM Somos. When cured, it is a ceramic-like material with a flexural modulus of 10,500 MPa, a heat deflection temperature of 260°C (at 0.46 MPa after thermal post-cure), a Shore D hardness of 94 and very low linear shrinkage.
DSM Somos says the resin also offers excellent side wall quality, which reduces the amount of finishing time required and makes it attractive for applications that requiring highly finished parts. As well as being suitable for rapid tooling used in injection moulding applications, Nanotool is also suitable for the production of high-quality models for wind tunnel testing and parts that can be metal-plated as prototypes for cast metal components.
Nanotool can be used with the stereolithography process to create tooling inserts capable of moulding hundreds or, in some cases, thousands of parts from thermoplastics such as polyethylene, polypropylene, thermoplastic elastomers, high-impact polystyrene, ABS, polycarbonate and glass-filled nylon. These moulded parts would typically be used for performance testing or marketing studies, though the quality and structural integrity of the parts mean that they can also be suitable as production parts for short-run applications, provided the relatively long moulding cycle time of 60–120 s is acceptable. For tooling that would traditionally require extensive electro-discharge machining, the rapid tooling process is likely to be more cost-effective than machined metal tooling. In addition, turnaround times can be very short, with moulded parts available in as little as three to five days.
As a guideline, DSM Somos suggests that Nanotool should be used for components up to approximately 100 mm in size with ribs no less than 1.6 mm thick due to the relatively brittle nature of the material. A minimum draft angle of 2 degrees is recommended and, although sharp corners can be produced, the company cautions that this can reduce the life of the tool. For complex components, hand loaded cores can be used, and metal inserts remain an option for tall or thin-walled features that would be difficult to tool in Nanotool.
So far we have discussed the use of Nanotool for rapid tooling, but the other application for which this material is proving popular is known as Metal Clad Composite (MC2) production. By coating a Nanotool part with a base layer of copper then a greater thickness of nickel, properties very similar to die cast or investment cast components can be created - but at a fraction of the cost. A metal-to-resin ratio of 20-30 per cent is said to result in a tensile strength similar to metals such as aluminium, zinc and magnesium. Alternatively, a coating of nickel just 0.05 mm thick can be sufficient to provide good shielding against electromagnetic interference. In both cases, MC2 components are being used successfully for testing and real-world applications.
DSM Somos says that MC2 parts can be three or four times less expensive than parts that are investment cast or machined from solid, depending on the size and complexity. Furthermore, MC2 parts can be created in as little as one week.
Prior to launching Nanotool, DSM Somos was already marketing Nanoform 15120, which is another material taking advantage of nanotechnology. Similar in some ways to Nanotool, Nanoform 15120 is a composite stereolithography material that incorporates non-crystalline nanoparticles to enhance its physical properties. In particular, Nanoform 15120 offers high stiffness, heat deflection temperatures of 265°C or more, exceptional dimensional stability and low moisture absorption.
DSM Somos is not alone in using nanotechnology to develop improved materials for rapid prototyping and manufacturing; 3D Systems proclaimed that its Accura Bluestone material was the first commercially available engineered nanocomposite resin for stereolithography (SLA) systems when it was launched in 2004. Accura Bluestone is capable of creating parts with high-stiffness, high temperature resistance, excellent dimensional accuracy and good resistance to moisture.
Capable of resisting temperatures as high as 250°C, the material is suitable for both high-temperature environments – such as in electronics enclosures and automotive engine bays - as well as for creating injection mould tooling. Other applications that benefit from the high stiffness and accuracy include wind-tunnel testing for the motorsports and aerospace industries, and the production of inspection and assembly jigs and fixtures. The combination of part accuracy and moisture resistance means Accura Bluestone can also be used for water-contact components in pumps and similar products.
Post-cured Accura Bluestone has a tensile modulus of 7600 to 11 700 MPa, a flexural modulus of 8300 to 9800 MPa and a Shore D hardness of 92.
Having reviewed some of the rapid prototyping and rapid manufacturing materials that utilise nanotechnology, it is also worth highlighting a novel technique that makes use of nanotechnology to modify the properties of parts built from conventional rapid prototyping and rapid manufacturing materials. RP Tempering is described as a solid freeform additive technology developed by Par3 Technology for use with parts built using stereolithography, laser sintering, fused deposition modelling and 3D printing systems. Whereas parts built using these systems are normally relatively fragile, the RP Tempering technology enables toughness to be improved considerably. In addition, Par3 has developed alternative treatments for enhancing electromagnetic shielding, flame retardance and chemical resistance.
As well as modifying a component’s bulk characteristics, RP Tempering also enables living hinges to function, snap fits to be used numerous times, and self-tapping screws to be inserted into screw bosses.
To use RP Tempering, the part has to be built with a series of tunnels and surface grooves, depending on the part's geometry. The tunnels are subsequently injected with the RP Tempering compound that contains multi-wall carbon nanotubes. Coating techniques are also used to apply RP Tempering compounds to the exterior and/or interior walls of the component.
When RP Tempering was first introduced, it was necessary to modify the CAD model prior to creating the STL file for rapid prototyping. However, Materialise has incorporated special functions in its 3-matic software that enables the tunnels and other features to be added directly to an STL file in a process that takes around 15 minutes. In Europe, the Temperman Initiative has been established to promote RP Tempering, which is available through a number of service bureaux. The Temperman website has a series of short videos that illustrate very clearly the dramatic improvements that RP Tempering can make to components.
Nanotechnology has already found its way into hundreds of consumer products because of the diverse benefits that are available. As the foregoing illustrates, nanotechnology is also starting to make an impact on the world of rapid prototyping and rapid manufacturing.