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 (Fig.1). When cured, it is a ceramic-like material with a flexural modulus of 10500MPa, a heat deflection temperature of 260°C (at 0.46MPa 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 (Fig.2). 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 60–120s 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 100mm in size with ribs no less than 1.6mm thick due to the relatively brittle nature of the material. A minimum draft angle of 2degrees 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 (Fig.3). 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
20-30percent is said to result in a tensile strength similar to metals such as aluminium, zinc and magnesium. Alternatively, a coating of nickel just 0.05mm 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 Nanoform15120, which is another material taking advantage of nanotechnology. Similar in some ways to Nanotool, Nanoform15120 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 11,700MPa, a flexural modulus of 8300 to 9800MPa and a Shore D hardness of 92.
