Logo
Prev
search
addthis
Rotate
Help
Next
Contents
All Pages
Browse Issues
Subscribe
Home
'
Metal Casting Technologies : MCT JUN 2018 (2ND QRT)
Contents
METAL Casting Technologies 2nd Quarter 2018 17 in the United Kingdom, there is a real concern about the lack of inspection standards at a time when the use of 3D printing is on the rise. “The advantage of AM is that it offers almost complete freedom when it comes to designing parts,” says Dutton. “Unfortunately this also makes the part very difficult to inspect. The more complex the component is internally, the more difficult it is for NDT. There are also challenges related to the rough surface finish, which limits the number of NDT methods which can be applied.” While some AM systems incorporate in-process monitoring, they use cameras to take snapshots of the layers as the item is being created. “The problem with this technique is that each new layer of powder can cover up part of the defect,” explains Dutton. Dutton is now working on a new inspection technique that uses laser ultrasound rather than camera imaging. The engineer hopes that this will eventually lead to the widespread adoption of 3D printing within mass manufacturing industries. “With NDT methods such as laser ultrasound there is a certain amount of penetration,” he says. “This means that you can look below the top layer and detect sub-surface defects in a non-contact way.” Tomographic techniques Another NDT technique that AM professionals are increasingly turning to is X-ray computer tomography (CT). Similar to a medical CAT scan, CT uses X-ray technology to penetrate various materials and sizes for internal part data, ranging from microprinted parts through to large castings. Most applicable in the preproduction stage of the manufacturing cycle, an industrial CT scan is able to validate and qualify prototypes and the first printed parts for various different materials, including mould components and metal and plastic printed parts. X-ray CT scanning can also serve manufacturing projects that require 100% validation of high value printed parts during production. If there are failures or errors during production as a result of temperature change or stress, the scan can be analysed to identify these internal failures quickly and accurately in three dimensions. CT scanning can play an integral role in the quality control process for inspecting small, highly complex, detail-oriented 3D printed parts, ensures they meet the requirements of fit, function and interchangeability. While the ability of X-ray CT to detect defects has a direct correlation with the size, complexity and composition of the AM part being analysed, in principle high scanning resolutions are possible, from millimetres to micrometres, and more recently nanometres. Design disconnect Additive manufacturing has opened up a whole new world in terms of product design. Engineers can now create complex shapes and combine multiple parts in ways that were either not physically possible or cost effective using traditional machining or injection moulding. But this added complexity has come at a cost. Many early AM adopters experiencing unsatisfactory results because they did not fully understand the requirements and limitations of the support structures, new materials and post-processing required to properly realise innovative designs. It has proven a real challenge to adapt traditional CAD design practices and simulation processes for AM, meaning there has long been a disconnect between the design engineer’s vision and the physical printed part. At present, core AM technology (namely material deposition) typically leaves an irregular surface. This may be fine for prototyping, but not for in-service, high-tolerance applications, and means significant post- processing is often necessary. Another problem is that original CAD programmes were not built to consider unique features of AM parts, such as infills and internal structures. Yet things are now changing, with many AM software develpers working to give the market a new standard for fully integrated, “screen to machine” CAD. This is exemplified by a new solution released last year by Siemens’ product lifecycle management (PLM) business, comprising integrated design, simulation, digital manufacturing, data and process management software. Sophisticated software The world of AM is continually innovating and pushing the boundaries. With 3D printers evolving beyond the capabilities of conventional 3D file formats such as STL (a file format native to stereolithography CAD software), more functionality has been required for quite some time. To overcome this constraint, a revolutionary new 3D printing format called 3MF (3D Manufacturing Format) has been developed by Microsoft, together with a range of other partners including AM software companies Autodesk, Shapeways and SLM Solutions. This enables design applications to send full- fidelity 3D models to a mix of other applications, platforms, services and 3D printers. Although 3MF has yet to be adopted by many software companies, it represents a quantum leap forward. While the STL format lacks complete model information, the 3MF standard contains complete model information in a single archive of manageable size, with mesh, textures, materials, colours and print tickets all included. Another key bottleneck for companies using 3D printing is the lack of traceability in the process, such as when changes are made to printing files. With increasingly stringent regulations, reporting and quality control requirements coming into play, particularly in industries such as aerospace and medical, this problem must be tackled if AM is to become as a viable manufacturing technology. RP Platform, a London-based AM software developer, has recently launched a new file versioning system that allows AM departments to fully trace their operations and better coordinate project workflows. This not only means changes to 3D printing files can be tracked, but that file conversion, repair and errors can be visualised. As users will no longer have to manually rename files or maintain duplicates of the same files, many could also benefit from improved efficiency. Four to the fore AM processes build three-dimensional components by using a laser to heat and fuse powdered material. Lasers are the most effective energy source in AM since the laser beam can transfer a large amount of energy into a micro-scale area, instantaneously to solidify or cure materials in air, enabling high-precision and high-throughput manufacturing. The drive for increased productivity from metal AM processes is relentless. A number of companies are now developing AM manufacturing systems that employ multiple lasers. Using multiple and higher power lasers can bring game-changing increases in productivity; in general, switching from one to two lasers nearly halves the build time. “Compact, multi-laser machines enable components to be built more quickly and more cost effectively,” says Marc Saunders, Director of Global Solutions Centres at UK-headquartered AM manufacturing system developer Renishaw. “This means AM is becoming cost competitive with conventional manufacturing processes in more and more cases.” Renishaw’s recently launched RenAM 500Q four-laser system is expected to speed up the AM process by up to four times, thereby broadening the market appeal of metal additive manufacturing. This will advance the technology into applications that are presently uneconomic, and potentially into new industries that have yet to embrace AM in production applications. The key driver for the RenAM 500Q is a new, innovative optical system. The system is a critical component within the AM system and was designed through a collaboration between Renishaw’s control, software and mechanical engineering departments. The company actually used AM to produce this component, allowing tighter packaging of the guiding mirrors and the incorporation of internal cooling channels to maintain precise thermal stability. With four lasers working over the entire build area, the RenAM 500Q maintains a highly precise relationship between the optical system and powder bed. This is enabled by a number of engineering developments, including sophisticated kinematic mountings that improve accuracy, set-up time and repeatability. Next generation printing As transformative as AM processes have been in enabling custom and complex parts, they are far from perfect. Using metal powders for AM means handling potentially dangerous materials, and thermal distortion issues are still a complicating factor. Enter the new wave of metal printing. Companies such as XJet, Desktop Metal and Digital Alloys are forgoing the established powder-based approach for one in which the metal powder is either encapsulated in a carrier liquid, or embedded in a filament, printed into a fragile “green body” (a structure 16 www.metals.rala.com.au Lattice Test samples, designed using Topology inc. Element software. Stochastic cell size of 0.5mm and strut diameter of 0.2mm, Ti64 and printed on a Renishaw AM250. An image of RPDs on a build plate inside Renishaw AM 400. RenAM 500Q four lasers for high productivity. Metal additive manufacturing system with automated powder sieving and recirculation. Close up image of laser melting titanium powder. FEATURE FEATURE
Links
Archive
MCT MAR 2018 (1ST QRT)
MCT SEP 2018 (3RD QRT) WHOS WHO OF METALS
Navigation
Previous Page
Next Page
