The first 3D printing machine was produced in 1991, a few years after the first 3D CAD software package was released. Since then, the two technologies have developed to become essential tools that engineers and designers use every day.
But, as with distant relatives sitting next to each other at a wedding reception, the relationship between 3D printing and 3D CAD is awkward. They have a lot in common, but are so unfamiliar that you have to force them to talk to each other.
An engineer who wants to 3D print a 3D CAD model usually has to use three separate software environments – the 3D CAD software itself, ‘middleware’ to translate the 3D model to a format suitable for the 3D printer, and then software to send the model to the printer.
Immature technology
The process is cumbersome and problematic. Engineers have to not only modify designs for 3D printing machines, but also deal with technical issues between the different software environments.
Danny Weber, vice-president of strategy and strategic alliances for Stratasys, says that to an extent the process is broken. “You lose associativity in the process. More importantly, it is almost impossible to fulfil the design intent when using 3D printing for manufacturing.
“Other fabrication technologies, such as injection moulding, are more mature. The designers were educated about them, and there are automatic tools to allow designing for these techniques in the CAD environment.”
Stratasys has been the dominant player in the 3D printer market after merging with Israeli firm Objet in 2012. Since then, Stratasys has been acquiring businesses and forging partnerships. Notably, it bought the hobbyist-orientated, desktop 3D printing company Makerbot in 2013.
Stratasys has also joined forces with 3D CAD supplier PTC to integrate its 3D printers into PTC’s Creo design software. The aim of the partnership is to eliminate the middleware and 3D printer software, so that the designer can send a part direct to the 3D printer from the same software environment in which they are designing.
Slow move to collaboration
PTC was one of the first companies to make 3D CAD available, with its original parametric modeller, ProEngineer, in 1987. Stratasys was the first company to build a 3D printer. Yet it’s taken nearly 25 years for them to collaborate and develop a ‘send to 3D printer’ button. This delay is principally because it’s taken that time for the 3D printing market to develop to a size large enough to make it worthwhile to do so. Weber says: “3D printers are becoming more prevalent – the market is mature enough now. Plus Stratasys as a company has reached a scale where it becomes worthwhile investing in integrating.”
The 3D printer integration in the latest release of Creo supports one printer, the Stratasys Objet500 Connex3. Other Stratasys printers will be added in future releases, but the support of just one machine is indicative of how early it is in efforts to integrate CAD software and 3D printers. Similar moves to integrate CAD and 3D printers among other CAD companies and printer suppliers are being driven by the 3MF consortium, which launched earlier this year. The initiative, which counts Stratasys as a member, aims to introduce a common file format for 3D printing.
The 3MF file format will improve communication between CAD software and 3D printers, and make the transition of models from CAD to printer more straightforward. It will reduce the time it takes to print a 3D CAD model and, printer suppliers hope, improve the users’ experience by letting them remain in their native CAD environment when 3D printing.
Increased integration between CAD and the 3D printer will help realise more benefits from the technology, says Weber. “3D printing requires adaptations. You are optimising for other elements, and there are weaknesses you need to compensate for in the design,” he says.
“3MF is a very big step forward to improve the workflow from CAD to 3D printer. Further integrations may be required to allow more advanced features. For example, the designer could benefit from knowing the specific materials that are currently on the printer, or knowing the tray size of the printer to decide if they can print in one shot or not.”
On a more advanced level, close integration should let users simulate and analyse parts before they are printed. “This will enable design functionality that takes advantage of the geometric freedom that 3D printing allows, such as generating lattices and topology optimisation,” says Weber. “The CAD environment will be able to create geometries and know what can and can’t be printed.”
Autodesk Within Labs is a London-based 3D printing bureau that has been working with engineering firms for 10 years, helping them to optimise designs for printing. The consultancy, which was recently acquired by CAD software supplier Autodesk and renamed Autodesk Within, uses software that was developed in-house to ‘generate’ designs that are optimised for 3D printing machines according to user-defined parameters.
These parameters can be weight requirements, maximum stress and displacement. The designs output by Within’s software feature variable-density lattice structures and surface skins that meet the user’s specifications.
As well as providing its consultancy services to end users, Autodesk is making the Within optimisation engine available to them too, enabling designers to automatically optimise designs for 3D printers. Autodesk sees the generative design features of the optimisation engine eventually becoming integrated into software packages in the rest of its portfolio, which includes 3D CAD package Inventor.
The optimisation software is compatible with three main processes: direct metal laser sintering, electron beam melting, and selective laser sintering. The first two are applicable to metallic materials, whereas the latter is applicable to plastics. Autodesk Within has been working with machine manufacturers such as EOS and Arcam for the past five years to ensure that the designs generated by its software are producible and self-supporting.
Dr Bhupen Lodia, head of design consulting for Autodesk Within, believes that generative design will be central to the future of 3D printing. “Generative design can increase design quality, efficiency and performance across the board,” he says. “It uses the computing power of the cloud to determine design alternatives set by the designer, based on parameters such as weight or strength.”
Embedded design rules
The Within engine uses the Nastran Solver as its primary structural finite element solver. Users can define real-world loading scenarios, which are used for the simulation and optimisation of the final output. The workflow has embedded design rules, which allow the optimisation to focus on the application or function while ensuring the optimised output is still producible on a 3D printer, by setting the build envelope and design resolution.
So, for example, the optimisation engine can make products lighter while optimising performance by fine-tuning the displacement for a given requirement, with the stress requirements being complied with by default. “The internal load paths of a design can be manipulated to output specific mechanical behaviour,” says Lodia.
An example of this process could be the sole of a shoe designed to allow for the correct distribution of loads on the sole of a person’s foot. Researchers are looking at applying lattices to impact-resistant structures. Another significant application is increasing the efficiency of heat exchangers by extending the effective surface areas and the turbulent airflow through them.
The consulting arm of Autodesk Within works in several sectors, including aerospace, automotive, industrial tooling and biomedical devices. Lodia says: “In particular, we are seeing an increased demand from the aerospace and automotive sectors, as they are focused on weight reduction, increased performance and ultimately reduced costs. Additionally, they have challenges with the certification and inspection aspects of the designs.”
Weber from Stratasys says that a growing number of engineering companies are adopting 3D printing for manufacturing. Airbus is using more than 1,000 3D printed parts in its latest A350 aircraft. Integration should see that adoption increase.
“Printer vendors have a vision of their technology being used for manufacturing and tooling and other manufacturing support,” says Weber. “Part of the challenge is to remove the barriers that inhibit adoption by manufacturers. Enabling design for additive manufacturing and improving the workflow from design to the printer is a key element.”
Another part of the vision is to reach a point where the technology is accessible to as many people as possible. “3D printing can be leveraged by any mechanical engineer to improve designs, during prototyping and also in the production of other technologies,” says Weber. “We’re making it easier to integrate 3D printing into existing workflows, to iterate and touch and feel each design. It’s a valuable tool.”
Lightweight lattices One of the most widely touted benefits of 3D printing is the geometric freedom it enables in designs. Complex lattices and the optimisation of topology can eliminate material to reduce costs and improve sustainability in products. Single-piece components can also be made with varying levels of wall thickness, producing flexibility and stiffness in different areas.
London 3D printing consultancy Autodesk Within’s work illustrates the kind of designs possible. One example is a loadbearing engine block. The original was a solid block where two fluid-carrying pipes merge into a larger pipe, which then exits the block at a right angle to the original direction. The traditional method of creating this component involved drilling two holes into the top of the block to meet another hole drilled into the side of the block. Where the pipes meet was a point of resistance, because of the sharp angle that interrupts fluid flow.
The new design builds the pipe into the block. A uniform cross-section can be maintained between the two smaller pipes and the larger pipe with a smoothly curving junction. This creates a more continuous flow that limits unwanted interruptions.
The block also had to withstand asymmetric loading from the top, so the under surface of the top of the block needed to be supported. The underneath of the larger pipe, and the junction, also needed to be supported. The design was built in steel on an EOS M270 machine.
Another recent example from Autodesk Within is the design of a roll hoop for a Formula One car. The roll hoop needs to be strong enough to withstand the high stresses a crash would incur, so designs are usually heavy. This is not suitable for maintaining a low centre of gravity, especially as the part is attached to a raised area of the vehicle.
The 3D-printed roll hoop is produced in a strong yet lightweight titanium alloy according to a design that includes a lattice that reduces weight while meeting aerodynamic and stress requirements.
Only the underside of the hoop’s face needed a small support structure to be added during the build as the rest of the design was self-supporting.
Common format
The 3D Manufacturing Format (3MF) consortium was launched in April. Its members include Microsoft, HP, Autodesk, Stratasys, Siemens PLM and Dassault Systèmes, which adopted the 3MF format in the latest version of its Solidworks software.
The consortium is creating 3MF so that design applications can send full-fidelity 3D models to a mix of other applications, platforms, services and printers. It aims to eliminate the problems associated with currently available file formats, resolving interoperability and functionality issues, and enabling companies to focus more on innovation.
The 3MF specification has its roots at Microsoft, which donated for industry adoption a 3D file format it was developing.
Key date in the diary for design engineers
The Engineering Design Show, which takes place at the Ricoh Arena in Coventry next month, has quickly become a popular date in the diary for design engineers in mechanical, electromechanical and electronics disciplines across the full range of industry sectors.
The aim of the show is to outline the sorts of technology, materials, components and processes that enable design engineers to work in a more efficient and streamlined manner.
Established in 2012, the event has more than tripled in size, and is expected to attract 250 exhibitors and more than 5,000 visitors. This year, in addition to the exhibition stands, the event features a conference with prominent industry experts giving presentations of top-level industry trends. Furthermore, there will be a schedule of technical workshops offering hands-on, practical advice in areas such as linear motion; test and measurement; rapid manufacturing; embedded software development; composites; and sensors and signal conditioning.
The conference has attracted some impressive names. Land Rover Ben Ainslie Racing will speak about the engineering strategy and challenges behind winning the America’s Cup, while Rolls-Royce will explain how materials data can be used to support a sustainable business.
Williams Advanced Engineering, meanwhile, will provide insight into the technology behind Formula E cars, while Covestro (formerly Bayer Material Science) will cover how the materials were developed for the Solar Impulse aircraft.
There will also be a presentation from Hybrid Air Vehicles, whose engineers will identify the key design features of the world’s biggest aircraft, the Airlander.
The Engineering Design Show takes place on 21-22 October in the Jaguar Exhibition Hall at the Ricoh Arena in Coventry.
More details on the show can be found at www.engineering-design-show.co.uk.