Paul Boughton
nanotechnology is also now offering advantages to new product development teams."Nanotechnology is now finding applications in numerous consumer products, ranging from sunscreen and cosmetics to...
Nanotechnology is now finding applications in numerous consumer productsranging from sunscreen and cosmetics to sporting goods and guitar strings. In the field of rapid prototyping and rapid manufacturingnanotechnology is also now offering advantages to new product development teams.
In this article we will look at materials for tooling and model buildingas well as an innovative technology that improves the performance of standard materials used for rapid prototyping and rapid manufacturing.
Heavily filled with non-crystalline nanoparticlesNanotool resin is one of the Protocomposite materials available from DSM Somos (Fig.1). When curedit is a ceramic-like material with a flexural modulus of 10500MPaa 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 qualitywhich 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 applicationsNanotool 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 orin some casesthousands of parts from thermoplastics such as polyethylenepolypropylenethermoplastic elastomers
high-impact polystyreneABSpolycarbonate and glass-filled nylon (Fig.2). These moulded parts would typically be used for performance testing or marketing studiesthough the quality and structural integrity of the parts mean that they can also be suitable as production parts for short-run applicationsprovided the relatively long moulding cycle time of 60–120s is acceptable. For tooling that would traditionally require extensive electro-discharge machiningthe rapid tooling process is likely to be more cost-effective than machined metal tooling. In additionturnaround times can be very shortwith moulded parts available in as little as three to five days.
As a guidelineDSM 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 andalthough sharp corners can be producedthe company cautions that this can reduce the life of the tool. For complex componentshand loaded cores can be usedand 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 toolingbut 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 nickelproperties 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 aluminiumzinc and magnesium. Alternativelya coating of nickel just 0.05mm thick can be sufficient to provide good shielding against electromagnetic interference. In both casesMC2 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 soliddepending on the size and complexity. FurthermoreMC2 parts can be created in as little as one week.
Prior to launching NanotoolDSM Somos was already marketing Nanoform15120which is another material taking advantage of nanotechnology. Similar in some ways to NanotoolNanoform15120 is a composite stereolithography material that incorporates non-crystalline nanoparticles to enhance its physical properties. In particularNanoform 15120 offers high stiffnessheat deflection temperatures of 265°C or moreexceptional 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-stiffnesshigh temperature resistanceexcellent dimensional accuracy and good resistance to moisture.
Capable of resisting temperatures as high as 250°Cthe 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 industriesand 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 11700MPaa flexural modulus of 8300 to 9800MPa and a Shore D hardness of 92.
Tempering technology
Having reviewed some of the rapid prototyping and rapid manufacturing materials that utilise nanotechnologyit 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 stereolithographylaser sinteringfused deposition modelling and 3D printing systems. Whereas parts built using these systems are normally relatively fragilethe RP Tempering technology enables toughness to be improved (Fig.4). In additionPar3 has developed alternative treatments for enhancing electromagnetic shieldingflame retardance and chemical resistance.
As well as modifying a component’s bulk characteristicsRP Tempering also enables living hinges to functionsnap fits to be used numerous timesand self-tapping screws to be inserted into screw bosses.
To use RP Temperingthe part has to be built with a series of tunnels and surface groovesdepending 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 introducedit was necessary to modify the CAD model prior to creating the STL file for rapid prototyping. HoweverMaterialise 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 15minutes. In Europethe Temperman Initiative has been established to promote RP Temperingwhich 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.
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