Improving safety and functionality in 3D printed automotive parts

Metal additive manufacturing, or 3D printing as it better known, is set to revolutionise the automotive sector, bringing numerous benefits, as well as innovations in part design and processing.

Already examples are emerging, such as the 3D-printed titanium brake caliper for the Bugatti Chiron. Produced as a single unit from titanium through the layering process in the build chamber of an SLM 500 multi-laser machine, it features a tensile strength of 1,250 N/sqmm and a material density over 99.7%. On testing the parts, Bugatti found the 3D-printed components sustained strength and  retained stiffness amid the high temperatures witnessed at the speeds of more than 375km/hour achieved by these high-performance sports cars.

When BMW redesigned the folding mechanism of the BMW i8 Roadster and built it in the metal-powder bed fusion chamber of an SLM Solutions laser machine, it found the part to be 10 times stiffer than the plastic injection moulded counterpart. It was also 44% lighter as it was built from AlSi10Mg. Traditionally the folding mechanism of the i8 Roadster’s soft top is cumbersome, loading the car with unwanted additional weight, and taking up boot space. The new folding mechanism reduces all of these unnecessary issues. BMW also optimised the design specifications so that the part can now be produced in greater quantities, since the reduction in support structures enables stacking of 238 parts per platform, realising a significant economic cost saving.

Dedicated teams from SLM Solutions, with strong R&D applications knowledge and service experience, work closely with companies on specific customer development projects. One such project, the LightHinge+ project, demonstrates not just the usual benefits of 3D printing in terms of weight reduction and efficiencies, but also addressed the safety requirements of parts when vehicles become involved in a collision. The LightHinge+ project combined three organisations – EDAG Engineering, voestalpine ADM Centre and Simufact Engineering – in the redevelopment of a vehicle hood hinge with stringent specifications and the requirement for weight reduction.

The exacting safety and functionality demands imposed on engine hoods demonstrate how complex the parts actually are. The response of the hood hinge is critical in the event of a pedestrian accident, as within a fraction of a second the hinge extends the distance between impact and engine components by raising the hood, thereby reducing pedestrian injury. However, complex kinematics are involved to trigger this instantaneous response. In the past this has entailed the use of around 40 components, intensive assembly and high tooling costs, due to the hinge systems being manufactured by stamping, casting or forging. Moreover, hinges made from sheet metal, for example, weigh around 1,500g each, adding considerable weight to every vehicle.

The redevelopment team applied bionic design, or biomimetic engineering, a process of adapting designs from nature that feature complex geometries best implemented in a selective laser melting machine. SLM Solutions systems feature multi-laser options, bio-directional recoating and closed-loop powder handling for safety with increased build speeds for complex and dense metal parts.

Implementing bionic design allowed the LightHinge+ engineers to develop an important additional function of predetermined breaking points on the structure. They were also able to integrate the connections for the gas pressure springs, along with mounts for the windshield wipers. Aside from these enhanced features and improved safety, initial topology optimisation of the design for minimal material requirements enabled a weight saving of 52% compared with the sheet metal construction, enabling the team to meet the specifications and a produce a better part.

The LightHinge+ project, undertaken by working closely with a team from SLM Solutions, provides just one example of the impact of 3D printing on automotive part manufacturing. Australian companies can now access a team of engineers to support individual customer project development, located both in Sydney and Lübeck, Germany.

www.raymax.com.au


Ultimaker expands S-line product family with Ultimaker S3

Ultimaker has unveiled the Ultimaker S3, the latest addition to its S-line product family of 3D printers. The Ultimaker S3 offers turnkey production capacity for anyone to achieve high-quality results.

The affordable desktop 3D printer has composite-ready performance and an efficiently small footprint to fit easily on any desktop. Packed with the latest technology, the Ultimaker S3 offers disruptive businesses a cost-effective way to adopt and drive in-house 3D printing.

The new Ultimaker S3 seamlessly integrates into Ultimaker’s open ecosystem. The feeder wheels are made of hardened steel and together with the CC print core, users can print with almost any 2.85mm filament – such as PLA, ABS, Nylon, third-party materials and abrasive materials. Engineers can design, test, and produce models and custom end-use parts with the widest range of materials for their manufacturing needs. The wider nozzle coverage ensures that no space is wasted, which offers an increased build-volume-to-size ratio.

The Ultimaker S3 contains an award-winning touch interface and predefined print settings that facilitate more precise 3D printing as part of any workflow. A heated build plate, advanced active levelling, a stiffer build platform and accurate stepper drivers result in the highest print quality of a machine in this form factor. The dual filament flow sensors can detect empty filament spools in the Ultimaker S3 and will automatically pause print jobs so that users can immediately replenish materials and keep the machine running seamlessly.

“I am proud that we managed to pack all the latest breakthrough technology into a machine with the form-factor of the Ultimaker 3,” said Paul Heiden, Senior Vice-President – Product Management at Ultimaker. “The accessible Ultimaker S3 is capable of reliably manufacturing smaller parts and models at a price-point that removes the barrier to entry for entrepreneurs and SMEs to adopt 3D printing. Now, anyone who wants to start leveraging Ultimaker’s flexible, powerful 3D printing system can do so and make full use of all materials with print profiles available in the Marketplace in Ultimaker Cura.

“We passionately believe that the ability for more businesses to affordably disrupt markets with rapidly developed, locally manufactured parts and models, makes the Ultimaker S3 a no-brainer. And we’re excited to see how our customers take advantage of this new opportunity.”

The Ultimaker S3 is available through Ultimaker’s network of global partners. Ultimaker has also launched its Ultimaker S5 Pro Bundle, offering manufacturers a full automated 3D printing workflow tested for unattended use and 24/7 3D print capacity.

www.ultimaker.com


Additive Manufacturing Hub – Lessons from Germany

In November, the Additive Manufacturing Hub and AMTIL led an Australian delegation on a tour of various manufacturing sites in Germany that are utilising additive manufacturing in their processes, to complement the group’s attendance at the Formnext exhibition in Frankfurt. Among the delegates was Matthew Harbidge of Charles Darwin University; here Matthew shares  his notes on what he saw on the tour.

The tour offered some excellent insights into the ways that others are engaging in the additive manufacturing (AM) industry, some of the general practices being implemented, and ideas regarding the future of the technology. We visited three sites: Bosch, FIT, and Toolcraft.

Bosch – Integrating 3D printing 
The Bosch facility was a modern mass production site that utilised CNC machines, robots, and people all working together to produce three main parts: high-pressure fuel pumps, gearbox solenoids, and drive-by-wire throttle systems. Currently the facility only uses “digital twin” for very small production runs and compares the real run to the simulated production run. They do not digitally trace their production components.

Bosch uses three main pieces of software for monitoring and reporting of the facility – these are  Nexeed MES, PowerBI, and Tableau. With these packages they can monitor machine outputs, variations and downtime, and plan maintenance. They are in the early stages of applying machine learning to solve production issues pre-emptively.

In the last three years Bosch has expanded its facility by adding in some AM machines: Dremel plastic printers, with Concept Laser and 3DS metal printers. All production line equipment was housed in plexiglass and aluminium extrusion frames. All parts are labelled internally with QR codes, and stations are set up around the facility that can scan or produce labels. The printer work area is fully enclosed for powder control, and they have a large amount of signage and labelling for personal protective equipment (PPE) and procedures. They currently outsource all their heat treatments except for aluminium.

The parts that they had on display were a mix of standard geometry test prints and actual Bosch parts. Our hosts mentioned some of the benefits of 3D printing and how they could be applied to some of their existing parts or be used to improve them. However, their main display part had no features that could not have been done with a CNC machine (curving internal geometries) and appeared to have a casting line.

The facility itself was excellent, with a very high value placed on safety, and obvious knowledge of powder-handling standards. A lot of time and money has been spent to reach this level. However, from a production side it appears they are still at the very early stages, and unsure of how AM will tackle any problems that they have.

FIT  One of the world’s largest printing bureaus
FIT is one of if not the largest printing bureaus in the world for 3D printed components. They produce more than 400k unique parts every year, not including production runs of like parts. They’ve been operation now for more than 25 years and produce plastic, metal, and other materials such as sand casts.

The opening presentation showed some of FIT’s print philosophies that they believe set them ahead of the crowd. They believe first in understanding the part function, translating this into a physical specification, not a design, then deciding what material and process should be used to create this part. They understand that AM isn’t the be-all-and-end-all of manufacturing, yet.

FIT has developed their own in-house monitoring software, which monitors their printers, part completion, and part layout in the machine, but does not individually monitor or track individual parts. They have a “booking” system used for allocation orders and times to equipment, but I couldn’t see what software it used.

Their manufacturing is split into two warehouses: one for plastics, one for metals. In the plastic warehouse they use a universal powder delivery system, connected to all the powder-based plastic printers, which reduces handling of loading machines. However, metal powder proved too variable or inconsistent to be delivered in this way. In the plastic area EOS powder transfer stations and in-house built stations were also used. For metal powder handling and transfer all equipment is designated to a specific material to prevent cross contamination. The metal warehouse was very clean. However, only one machine was running, which was quite odd given most of the prints would typically take several days.

FIT currently outsources most of its heat treating, though the recent installation of a new hot isostatic pressing (HIP) machine may change that.

The FIT team generally spend the day preparing the printers with powder, files, substrates, and processing printed parts. At night the printers are preheated and begin their printing. They do not typically fill the print volume with parts. Instead they prefer to shorten part lead times, at the cost of additional labour per print. For example, if they have two different parts with 5 each to be made, they won’t put them together in a print; they’ll allocate them to different printers to reduce the turnaround time. FIT also prefers for at least 30% of its printers to be unloaded at any time, so that if it receives a large order that requires a short turnaround time, the team can process it.

The FIT team clearly know how to produce parts for AM and have solidified the company’s place in the AM world as innovators who are ahead of the curve. I look forward to watching them grow and branch out in the future.

Toolcraft  Producing parts for multiple sectors
Toolcraft is also approximately 25 years old and prides itself on making precision components for a variety of industries. The company produces components for aerospace, medical, biomedical, turbines, and more. The team pride themselves on a sense of family and community, where every employee is given a key. The company has only recently begun adopting AM it has been  engaged in advanced manufacturing since the beginning. It produced the first flying parts for Boeing, Airbus, and Pratt & Whitney.

The first port of call during our site tour included the apprentice’s station and several very large Seco/Warwick vacuum furnaces. There were large, powered hexagonal workstations with tool cabinets located underneath. There was also a significant number of Hermle C30U and DMG  MORI CNC machines.

Toolcraft is partnered with Trumpf, so it has several pieces of equipment provided by Trumpf, including Trumark 7000 laser engraving machines, Truprint 3000 printers, TruCell LMD machines, and all Trumpf powder handling equipment. Toolcraft also has Concept Laser printers. It uses two types of co-ordinate measuring machines (CMMs), which are both used to ensure a part meets specifications: a Zeiss Accura CMM, equipped with a 1.5-ton granite block; and a DEA Global machine. All required parts are double-checked on the different machines.

Toolcraft implements constant environmental monitoring and replacement of the air in the AM rooms. In the AMA room, a portable workstation is used for each material, with the required PPE, a RuVac powder vacuum cleaner, and the print plans. Every tool and printer had an allocated material and serial number. There are individual powder handling rooms per material type, such as an Inconel room with both 718 and 625, a Ti room with 64 and CP, and an  aluminium room. Each material has its own full handling system to prevent cross contamination.

Toolcraft analyses both powder and part for grain sizes, composition, microstructure, and density, as well as static, dynamic, and fatigue-testing rigs for the components that they make. Unfortunately, we weren’t able to see this section. Coupons are printed with all parts for testing, and dye pen NDT is conducted on printed parts and all flying CNC parts.

Toolcraft also has a printer booking/job system displayed on a large TV on the wall. It use Mastercam and Siemens NX Cam for its CNC machines, as well as SAP ERP production and part tracking for all of its machines. It is not as automated as the Bosch site.

The Toolcraft facility was in my opinion by far the best site. They had combined procedures, powder handling, manufacturing together seamlessly to produce real parts that are designed for their task. Parts that benefitted from CNC machining would be machined; parts that benefitted AM production would be produced via AM.

Led by AMTIL, and generously supported by the Victorian Government, the Additive Manufacturing Hub has been established to grow and develop Additive Manufacturing capability. To find out more about the AM Hub, contact John Croft, AM Hub Manager, on 03 9800 3666, or email jcroft@amtil.com.au.

www.amhub.net.au www.cdu.edu.au 


Wire AM– A new additive technology

Additive manufacturing is a field where groundbreaking innovations are emerging all the time. One particularly promising new technique is wire-fed additive manufacturing, writes Alex Kingsbury.

Metal additive manufacturing (AM) has certainly taken the world by storm. With the ability to create shapes not previously thought possible, this revolutionary, Industry 4.0-enabling technique has backers from a range of different industries all over the globe. However, when metal AM is mentioned, the first thought is usually of a laser-powered machine fusing metal powders layer by layer.

Certainly, this has been the predominant technique with a vast amount of machine sales dedicated to laser powder bed fusion (LPBF) since the advent of commercially available AM. But new and intriguing metal AM technologies have been making headway of late and offering a point of difference to the commonly accepted LPBF systems. One such technique is wire-fed additive manufacturing.

The concept is very simple: it is based on traditional welding, but rather than welding components together, a weld bead is laid upon another weld bead. This process is repeated until there is a series of weld beads welded successively, such that they create a three-dimensional shape. The process is controlled by a robotic arm and the shape is built up on a substrate material (a base plate) that the part can be cut from once finished. The shape is considered a ‘near-net shape’: it is close to the final part shape but usually requires additional machining to achieve final part shape and tolerance.

This process has many benefits over both LPBF and more traditional manufacturing techniques such as casting, machining and forging.

Wire feedstock

As the name suggests, welding wire is the sole feedstock for wire-fed AM, meaning established supply chains can provide a feedstock source. Numerous certified alloys are readily available to build parts with. Often this means that moving to wire AM from a traditional manufacturing process does not need to involve a change of alloy, as the same alloy of the exact specification can be sourced through a global supply network. If an alloy can be welded, it can be used in a wire AM process.

Operationally, using wire as a feedstock makes life in the workshop much easier. Changeover time between alloys is straightforward as a new wire is inserted and there is minimal clean-up after the previous build. Additionally, working with wire is inherently safer than other AM feedstocks such as powders. It is not reactive, nor can it be inhaled or irritate the skin.

Properties

Parts made via wire AM have been proven to be stronger than parts made via forging or casting. As the wire feedstock is a 100% dense input material, there is negligible porosity induced in the fabrication process, leading to a very dense final part. Additionally, the wire AM process enables better control over deposition rates, and therefore has better control of cooling rates, enabling processing to be tailored to the working alloy. Improved material properties mean parts that once had to be constructed of solid material can be built as thin-walled parts. This reduces material consumption, improving the cost basis and overall competitiveness with traditional techniques such as casting.

For parts of medium complexity that are forged and machined, wire-fed AM can be an excellent alternative process. Typically, a wire AM part undergoes a final machining step to remove surface irregularities and ensure a smooth surface. The material machined away usually amounts to 2% to 10% of the total material deposited. Compared with high ‘buy-to-fly-ratio’ parts – where in some cases up to 90% of the original starting material must be machined away – this presents a significant material and cost saving. This is especially true for high-value materials that are difficult to machine such as titanium and nickel superalloys.

Like most AM processes, wire AM is most suitable for low to medium-volume production, as set-up and tooling costs are minimal. This lack of tooling also increases speed to market as lead times are significantly reduced. Increased speed to market assists with product development, allowing in-field testing to feedback to further design iteration, which the wire AM process can very flexibly accommodate. This lack of tooling can also assist with reduction of lead time for critical spares. Using wire AM, lead time can be reduced from months to days, meaning a business no longer needs to maintain large inventories of critical spares.

Using wire AM, part size becomes virtually unlimited. The process is only constrained by the size of the workshop and the reach of a robotic arm. As the process utilises a gas shroud, reactive materials such as titanium and aluminium can be easily processed. Of course, just because you can, does not mean you should. Exceptionally large items (in excess of 2m) tend to require excessive fabrication times and can make wire AM uncompetitive. Likewise, very small items (less than 20cm) tend not to be cost-competitive. However, like most manufacturing technologies, this is material and part-requirement dependent. Wire AM has a sweet spot where the technology is best put to use; usually for medium size parts of medium complexity. This applies across all metals and part functions.

Made in Australia by AML3D

Andy Sales knows this value only all too well. With a background in welding technology, Sales went to Cranfield University in the UK to complete his Masters in 2012. Cranfield had been developing a wire AM process and this inspired Sales to return to Australia to establish AML3D, a service bureau based on wire AM technology. In addition to commissioning its own wire AM-based system, AML3D has also developed a software package that integrates material-processing parameters with its robotic cell. These sets of material-specific parameters have been developed in-house by AML3D, and the team has been rigorous in ensuring they can achieve repeatability and reliability in their process.

But far from being content with that, Sales has ambitious global plans for AML3D. The company is planning a production facility in Singapore in the near term, with the ability to further expand that capability. This is driven by demand from the Singapore marine hub, as the location is a strategic hub for commercial shipping routes.

Sales recognised the applicability of wire AM for shipping early on. Ten months after establishing AML3D in Adelaide he secured certification from Lloyd’s Register, the global shipping industry accreditation body. Being a certified provider gives customers the assurance that work is being performed to stringent quality standards. With certification in place, AML3D was quick to deliver its first part to a marine customer: a set of martensitic stainless steel wear rings.

The rings were normally fabricated via a forging process, but this required an additional heat treatment post-processing step. The total lead time was six-to-eight weeks, which as a long lead item was either held in a spares inventory or replaced prematurely. Using wire AM, AML3D was able to manufacture the rings for the same cost, but was able to reduce the lead time to a few days. This is a real game-changer for ships in dock for a limited time.

In addition to the marine sector, AML3D is also engaged with Boeing. For the aerospace industry, reducing material wastage is key to profitability, particularly with expensive, high-value material such as titanium, where as much as 80% of the starting material ends up as chips or swarf – a low-value titanium waste stream. Boeing in particular has had a long-standing interest in pursuing wire AM, and has been working with Norsk Titanium, a company that uses a wire AM process that employs plasma as a heat source. Working with Boeing, Norsk Titanium has received Federal Aviation Administration (FAA) certification for two structural aircraft parts in the US.

An aluminium jet engine cover plate manufactured by AML3D for an unnamed client showcases the benefits of wire AM when compared with machining. The cover plate was ordinarily machined from a 30kg billet and took four days of non-stop machining to produce. Using wire AM, a final machine of the near-net shape took just six hours to finish. Likewise, an aluminium wing rib, machined from plate, saw a 70% reduction in waste and a 60% reduction in cost. With those figures it’s hardly surprising that aerospace players across commercial and defence sectors are taking note of wire AM.

A new machine

To address the need for onsite production, especially in remote locations where spares inventories can be a real pain point for companies in the resources sector, Sales has created a packaged wire AM turnkey solution. Being guided by Industry 4.0 principals, the system integrates wire AM with machining and is controlled via AML3D software developed specifically for this hybrid solution. It means that customers can develop a digital inventory and produce a fully finished part onsite in days if not hours.

Selling this system, and the wire to be used in it, eases the pressure on the AML3D facilities in Adelaide and Singapore, and optimises the manufacturing-on-demand capabilities of wire AM. The machine is the first of its kind to be offered on the market.

Despite the outstanding possibilities of wire AM, AML3D is part of only a handful of wire AM-based businesses around the globe. RAMLAB in the Netherlands is the only other active service bureau, notable for its wire AM-produced ship propeller. MX3D, also in the Netherlands, uses a similar concept and in 2015 showcased an eyecatching demonstration of a robot 3D printing a bridge in mid-air. Norsk Titanium and Sciaky Inc. both produce wire AM systems – the former with a plasma-based process, Sciaky with an electron beam solution.

Like any new technology, it takes time for applications to develop and the benefits to proliferate through industry. Yet it is encouraging to see a small company in Australia with global connections taking the lead. No other wire AM companies around the world have made quite the progress that Sales and the team at AML3D have, with an established global presence, high-profile partnerships in place, and a business model poised for growth. Australia is fortunate to have a company right on our doorstep taking on this next frontier of additive manufacturing.

Alex Kingsbury is an Additive Manufacturing Industry Fellow at RMIT University.

www.aml3d.com


Post-processing — Enabling additive manufacturing

Some form of post-processing is inevitable when using additive manufacturing (AM) technologies, but particularly for serial production applications. Joseph Crabtree considers the importance of post-processing in the production process chain and highlights an emerging solution.

There are undoubtedly many benefits associated with the use of AM as a production technology. Manufacturers can not only build complex parts in one piece that were previously impossible, but they can also build stronger, lighter-weight parts, reduce material consumption, and benefit from assembly component consolidation across a range of applications. These advantages have been well documented during the last 10-20 years as AM has emerged as a truly disruptive technology for prototyping and production, invariably seen as enabled by the additive hardware that builds the parts. In reality, however, this is a partial picture, particularly for serial production applications. AM systems are actually just one part — albeit a vital part — of an extensive ecosystem of technologies that enable AM, both pre and post-build.

By focusing just on the AM build process, a fundamental part of the production process chain is often overlooked, namely post-processing once the part is out of the AM machine. Manufacturers using (or considering) AM for serial production applications need to first identify the appropriate process for their targeted application. From there the post-processing requirements must be identified and evaluated – otherwise the use of AM as a viable alternative to traditional manufacturing processes may end up being negated completely.

Post-processing for AM

Post-processing is actually an umbrella term for a number of stages that parts may need to go through after they come out of the AM system and before they are fit for purpose. Post-processing can include any of the following: excess material removal; curing/heat treatment; support removal; machining; surface finish processes (such as bead blasting); colouring; and inspection.

Post-processing is often the elephant in the room when it comes to the uptake of AM as a production tool. For AM production applications, post-processing is a considerable element of the overall cost-per-part, representing anything up to 60% of total cost. Support removal and other post-processing activities are often labour-intensive, and therefore costly and time-consuming. In addition, there is often a necessity for post-processing to enhance final part characteristics, in terms of functionality or aesthetics.

This is why the issue of post-processing is so important when looking at the viability of AM for serial production: because it is often the area where the technology falls down as a competitive manufacturing technology. The post-processing conundrum needs to be confronted head on with an ecosystem-based approach to each application — from end to end. This means joining the dots from product conception through to final product.

To a certain extent, post-processing can be cauterised by a focus on Design for AM (DfAM) to reduce the necessary post-processing steps. Success here will depend on how well the designer understands the intricacies of the AM process and the specific capabilities of the system they are using; how to orientate the parts in the machine; and how to generate optimal support structures for build and removal. In general, post-processing requirements for a given application depend on the geometry of the component and how well it is designed for manufacturability using AM.

However, regardless of how well a product is designed for AM it cannot negate the need for post-processing for all AM processes. The problem is that for an industry that calls itself disruptive, manufacturers are still largely post-processing parts the same way they did 100 years ago, with the requirement of significant manual intervention. And this is slowing the whole process chain down for production applications of AM.

An innovative approach to AM post-processing

The fundamental mission of my company, Additive Manufacturing Technologies Ltd, is to confront this problem head on through the development of innovative digital and automated post-processing solutions that increase efficiency and reduce the overall time and costs of production with AM, specifically with polymer AM processes and thermoplastic materials.

There can be no argument about the increased number and improved nature of the thermoplastic materials palette available for AM processes in recent years. Alongside these material developments, the AM systems that produce thermoplastic parts have also significantly improved in resolution, accuracy, repeatability and overall quality, and they are consistently meeting industrial requirements for exacting prototyping, tooling, and some production applications.

However, the critical mass of production applications remains lower than they otherwise might be due to the limitations placed on the overall process chain by the post-processing phase. This is because powder-bed processes — which require significant powder-handling and removal post build — also invariably require infiltration operations, as well as finishing processes, particularly if aesthetics are important alongside the strength advantages that laser sintering offers. If coloured parts are required, this is also applied in the finishing stages of post-processing.

With filament thermoplastic material processes, the very nature of the AM process (no matter how refined) results in a stepping effect. The traditional post-processing steps required to eliminate these process-specific results are considerable, costly, and time-consuming. However, an automated post-processing solution for smoothing high volumes of thermoplastic polymer parts to an injection-moulded surface quality would remove one of the biggest hurdles to the serial production process chain. Here, I am talking about parts 3D printed using the laser sintering, multi-jet fusion, high speed sintering, and fused deposition modelling processes for specific material types including Polyamide/Nylon, flame-retardant Nylon, glass-filled Nylon, ULTEM, PMMA, TPU, and TPEs.

This is exactly the solution that we envisaged, developed, and commercialised with our PostPro3D range of hardware, which integrates new systems, software and virtual services. The simplicity and speed experienced by the user belies the intelligent and complex capabilities of the system, which is built on the proprietary BLAST process.

Simplicity is the key. Post-build, the 3D-printed parts can be removed from the machine, loaded onto a rack, and placed into the PostPro3D post-processing chamber. The user then selects the appropriate program and the process starts and runs for 90-120 minutes, after which the parts can be removed, inspected, and are fit for purpose.

For anyone wondering what happens to the parts during those 90 to 120 minutes, they are subject to a physiochemical process that involves converting a proprietary but wholly safe solvent into vapour, under precisely controlled vacuum and temperature conditions. In turn, this precisely refines the surface of each part to ensure a perfectly smooth finish, equivalent to that of an injection-moulded part. Moreover, the process seals and strengthens parts, essentially improving their mechanical properties— such as elongation at break — compared with how parts were when they came out of the 3D printer.

The intelligence of the PostPro3D systems goes beyond their physical process capabilities, as they have been designed to be connected through an Industrial Internet of Things (IIoT) network, where vital data is analysed in real-time. This allows for new insights on process performance, which can subsequently be shared amongst the global fleet of PostPro3D machines, and made available via software updates to continually upgrade performance – all while protecting individual IP. Moreover, this connectivity capability also allows for integration with other intelligent devices and workflow automation software across the production process chain.

What all of this points to, I believe, is the continued need to work towards developing whole process chains that will help to convince AM users, and potential AM users, that the transition to AM for an increasing number of production applications is worthwhile and not nearly as complex as it was even a few years ago. This demands a unified approach — across the AM sector itself — to develop more capable and connected systems, while simplifying the overall process to provide economically viable, automated solutions. This can be achieved through partnerships and collaboration – Additive Manufacturing Technologies Ltd has been proactive in this area, working with Mitsubishi Electric and several other companies.

Automated turnkey hardware for post-processing — such as the PostPro3D range — is certainly a huge step forward for the post-processing stage of the production process chain with AM. However, there are still more steps to take in terms of wholly connected, customised, end-to-end digital manufacturing systems.

Joseph Crabtree is the founder and has been the CEO of Additive Manufacturing Technologies.

www.amtechnologies.com


EOS – Additive manufacturing enables Australian spine surgery innovation

The cost of treating lower back pain in the US has been estimated at $90bn per year in 2008, with a further $10bn-20bn in costs through lost productivity. A significant portion of the expense is attributable to spinal fusion surgery. Melbourne-based company Anatomics seeks to improve the efficiency of fusion surgery by reducing the manufacturing and supply cost of equipment and optimising the workflow within surgery without compromising clinical outcomes.

Anatomics has developed an innovative solution involving a custom patient-specific kit, SpineBox, that is 3D-printed using EOS’ selective laser sintering (SLS) technology in Nylon 12 powder. The SpineBox kit greatly simplifies minimally invasive transforaminal lumbar fusion surgery (MIS TLIF) and can be adapted to support most spinal fusion techniques.

Anatomics is an Australian-owned medical device company that has been manufacturing and marketing surgical products to surgeons locally and internationally since 1996. Anatomics pioneered CT scan-derived surgical implant technology and was first to market with an innovative, quality product that assisted surgeons to produce better surgical outcomes and save valuable operating theatre time. The company’s customers include neurosurgeons, plastic & reconstructive surgeons, oral & maxillofacial surgeons, orthopaedic surgeons, ENT surgeons and thorasic surgeons.

Using patient imaging in the form of computed tomography (CT) data together with custom planning software developed by Anatomics, a patient-specific solution is designed involving screws, rods and an intervertebral spacer (cage) for each MIS TLIF procedure. A 1:1 scale model of the patient’s spine is 3D printed with stereolithography apparatus (SLA) or EOS SLS from Nylon 12, and provided for the surgeon and patient to verify the surgical plan pre-operatively.

Patient-specific SpineTube muscle retractors and anatomically matched templates for surgery are also manufactured from EOS SLS Nylon 12 and sterilised. Based on preoperative measurements, the required titanium implants are pre-ordered and packaged with the SLS Nylon 12 instruments and provided as a SpineBox kit to the hospital before surgery.

The pre-planned specifications for the spinal construct can be mapped into the bony spine from the skin surface using the template and stainless steel pins known as Kirschner wires, with minimal radiography. Once deployed, the Kirschner wires provide a railroad for all subsequent instrumentation. The patient-specific SpineTube muscle retractor manufactured to match the skin to spine depth is then temporarily affixed to the spine with an insert and locking screw. The unique insert doubles as an osteotomy guide. Together, these novel 3D-printed instruments facilitate nerve decompression, fusion cage implantation, and accurate completion of the spinal construct.

Anatomics had a simple decision to make when deciding on the optimal technology for the required 3D printed components. EOS SLS Nylon 12 was the obvious choice as it is the virtual standard for highly accurate, biocompatible (for transient use), and mechanically strong components for surgical cutting and drilling guides worldwide. EOS’s reputation for engineering and after-sales support excellence was also a critical factor that swayed Anatomics behind EOS technology.

Spinal surgery is a complicated business requiring an extensive, costly support network. The SpineBox method of pre-planning surgery and manufacturing customised devices developed by Anatomics and enabled by EOS has the potential to realise significant time and cost benefits to the healthcare system. As of August 2019, the system has been used in more than 300 patients in Australia, and Anatomics is set to export the technology globally in 2020.

EOS will be a critical supply partner in that global expansion. Medical companies in Australia have increasingly come to rely on EOS’s additive manufacturing solutions to produce orthopaedic implants, surgical instruments, orthotics, orthosis, dental devices and other medical devices.

John Hart offers world-class additive manufacturing solutions from EOS in Australia. As well as the necessary materials and systems for additive manufacturing, EOS provides comprehensive market knowledge and a precise understanding of specific development processes in the field of medical technology enable EOS to collaborate closely with a strong network of partners. From rapid prototyping to series production, EOS provides comprehensive and competent advice and continuous support to customers during the entire development and production process.

Every person is unique. Therefore, optimal patient care requires medical products that provide a perfect fit. There is a high demand for one-off components and components produced in small production runs whose materials and manufacturing standards have to fulfil extremely stringent quality requirements. This also applies to specialised surgical instruments and medical devices. In addition, these products must be made available quickly and cost-effectively.

Additive manufacturing is meeting these exact requirements while paving the way for improved, patient-specific medical care. Additive manufacturing enables producers to come up with faster, more flexible and more cost-effective development and production methods. Unlike conventional manufacturing methods, it allows maximum design flexibility, enabling the implementation of innovative functions. Consequently, test series, prototypes, patient-specific one-off parts and small production runs can be manufactured at a profit.

www.johnhart.com.au/additive-manufacturing
www.anatomics.com


New design processes revolutionising 3D metal printing

Although the history of SLM Solutions, headquartered in Lübeck, Germany, is relatively short, the company’s founders may never have imagined how far the technology they helped pioneer would advance in such a short time.

Early-stage development of selective laser melting (SLM) saw the first commercial machine delivered in 1998. It met the specifications of making ‘unbreakable’ metal parts and stood as a testament to the two pioneers Matthias Fockele and Dieter Schwarze, who together worked in conjunction with researchers from the Fraunhofer Institute of Laser Technology.

Since then, 3D metal printing has evolved into one of the greatest influences on metal part production in recent history. The SLM process sees parts built in a chamber layer by layer with metal powder injected in a controlled manner then melted by laser beam to form a strong, solid structure. The technology has fast evolved from single lasers passing over the powder melting it layer by layer, to multi-lasers with high wattage increasing build speed, product quality and reliability, while reducing costs.

In a recent interview, Dr Simon Merk-Schippers, Director – Business Development for Aviation and Aerospace at SLM Solutions, said: “Lightweight construction, functional integration and production costs are ongoing topics. In addition to the aerospace industry, space travel, especially the launch market is undergoing a strong change. There is more and more rivalry and therefore more intense competition. Of course, this also leads to price pressure. It is interesting to note that smaller companies are gaining a competitive advantage by flexibly using our SLM technology.”

Fockele and Schwarze may never have imagined the advantages SLM would offer todays engineers, as the technology has presented new opportunities for changes to design specifications, and the realisation of complex parts that were once welded together can now be made as a single unit.

Recently Berlin-based engineering start-up CellCore produced a single-piece thrust chamber and injector for a rocket propulsion engine in collaboration with SLM Solutions, reducing numerous parts into one. The internal structure manufactured using SLM Solutions technology could not have been made using conventional methods. A rocket engine sustains exceptional heat levels during propulsion, so complex filigree cooling channels were integrated into the internal structure during the build process, increasing the efficiency of a combustion process that generates extremely high temperatures.

Biomimetic engineering

The thrust chamber by CellCore is another step in the realisation of 3D metal printing capability, a huge step beyond the 19-parts-into-one aircraft fuel nozzle developed by GE just a few years ago. But how was CellCore able to print such internal complexity? CellCore simply looked to the biological designs found in nature.

A dog is an amazing chemical detector. They inspect our clothes, carry-on luggage and bags for contraband items when we arrive at airports; they traverse war-torn fields planted with deadly explosives, sniffing out danger. Man-made devices have not been able to take the place of the nose that nature designed for our canine buddies. Recently, researchers ‘mapped the sniff’: the channels and breathing processes of a dog’s nose, in a bid to simulate or mimic what nature created to improve detection devices made by man.

Sharks are famed for their speed, so when engineers from Airbus attempted to understand shark speed with the aim of transferring this knowledge to improve aircraft speed, they were surprised to find that shark skin was composed of millions of small tooth-like riblets. These well-formed riblets had been adapted to serve two purposes, one of those is as a bacteria-repellent device, and the other has the purpose of enhancing the sharks’ swimming speed. Mimicing the skin structure Airbus developed small ‘riblet’ patches and fitted them to jetliners in airline service over two years. The findings revealed nature’s ‘shark skin concept’ was a highly suitable aircraft covering long-range flights.

These examples mimic nature, so why not look to natural structures surrounding us rather than invent new ones? Unlike artificial intelligence (AI) nature has been testing, trialling and fine-tuning structures, making adaptations and finding ‘best’ solutions for eons. Given this availability, bionic experts, engineers and computer software developers can imitate or mimic such biological processes and structures to optimise metal forms with the ability to make 3D printed metal parts lighter, more rigid or more stable. Today we are witnessing the emergence of a significant field known as biomimetic engineering where designs from nature are successfully leveraged into today’s product development, making for highly functional and effective products.

While a relatively new field of design, but already filling research journals, biomimetics is finding its way into a number of fields benefitting from the timely development of selective laser melting technology, 3D metal printing. CellCore GbmH in collaboration with SLM Solutions AG has developed a complex, highly functional thrust chamber for a rocket propulsion engine in a single build.

Biomimetic engineering reaches the space industry

Bionic experts, engineers and software developers at CellCore have developed software that optimises technical structures based on the internal structure of bones. CellCore believes there is no limit to the application of bionic engineering principles to optimise products across a range of industries. Already they have developed parts for racing cars with exceptional success, winning the BASF’s “Best Use of Fibre Reinforced Plastics” design.

Having reviewed the manufacture of office chairs, tram cars and orthopaedic products, CellCore have now applied the geometric design principles of biomimetic engineering to a groundbreaking structure in the form of a rocket propulsion engine: a single-piece thrust chamber and injector. By using SLM, the engine was manufactured in nickel superalloy IN718 to satisfy the aerospace industry’s strict requirements for materials.

IN718 is a precipitation hardening in nickel-chromium alloy with exceptional tensile, fatigue, creep and breaking strength up to 7,000 degrees Celsius. This hard material is difficult to process using conventional methods, but melting nickel-chromium powder based in a geometrically proscribed design in an SLM280 laser machine, reduced the inherent difficulties and costs of conventional manufacturing, while resulting in a more complex structure never before achieved.

Recently, Rolls Royce has sought the help of SLM Solutions by implementing quad-lasers that use multi-laser optics together with a bio-directional recoating mechanism for the development of aerospace components. The SLM500 laser systems have four lasers and can achieve build rates of up to 171 cubic centimetres, suitable for high-volume processing. The company aims to implement its expertise and knowledge of building 3D metal aerospace components to a system that offers far more opportunities for product optimisation.

Biomimetics in the automotive industry

Car part manufacturers have been quick to take advantage of the opportunities on offer with SLM to create efficient and economically attractive products.

Hirschvogel Automotive Group, a producer of high-strength parts for the automotive industry with plants in three continents, has one arm of its business tasked with part development and the testing of innovative products and high-strength components optimised for series production. Fully exploiting the benefits of ‘bionic design’ Hirshvogel Tech Solutions leveraged methods and structures developed by nature to produce a car steering knuckle, the automotive part that attaches to the suspension and steering system.

Using Aluminium AlSi10Mg resulted in an overall weight reduction in the part; however, by utilising bionic engineering principles a significant weight saving of some 40% in the neck area was achieved – a saving not possible in a conventionally forged part. This came about as the team developed specific Computer Aided Technologies (CAx) allowing them to fully optimise the design.

Part variants, initially based on solutions from nature, were assessed before being selected to meet the appropriate calculations. The use of biomimetic engineering allowed the reduction of weight in targeted areas as against a constant in the overall weight. Built as a single unit in the chamber of an SLM500 system, final tests were carried out on tensile and notched bar specimens achieving the required forecast test values.

What the future holds

Predicting the future should be left to Nostradamus, however, what seems certain is a rapid uptake of 3D metal printing as industry sectors realise the potential opportunities and value of optimising design through geometries in bionic engineering. The change, or interruption to conventional manufacturing, becomes more evident day by day, as differing fields of part production realise the challenging and exciting technological potential of additive manufacturing.

www.raymax.com.au

www.slm-solutions.com


AmPro Innovation – Production-ready printing

Additive manufacturing is evolving fast, with new breakthroughs happening all the time. But questions persist over its potential to have a truly disruptive impact in a production setting. That’s where AmPro Innovations comes in. By William Poole.

AmPro Innovations designs and manufactures 3D metal printers, including the critical powder management systems required for the production of advanced metal parts. Established to bring fast and lower cost printers to market for industrial and research applications, AmPro Innovations was founded three years ago by Professor Xinhua Wu, currently Director of the Monash Centre for Additive Manufacturing. Since long before her time at Monash University, Wu has been building an impressive record of achieving in materials science and additive manufacturing, most notably her pioneering work in developing the first 3D-printed metal parts certified for use on commercial aircraft. Operating from a small facility on Monash’s campus in Notting Hill, in Melbourne’s south-east suburbs, AmPro designs and manufactures metal-based 3D printing technology, drawing on the expertise of Wu and her team.

AmPro Innovations identified several key gaps in the emerging 3D printer market: a fully inert system for printed part compliance; printers designed for industrial applications where the full ‘powder to part’ process speed is critical; and capabilities for emerging materials demanded of advanced applications.

“Professor Wu is a world leader in understanding metallurgy and its relationship to laser-build strategies,” says Anthony Lele, who runs Commercial Operations & International Sales at AmPro. “That’s really important: understanding that 3D printing is a relationship between material and process. If you don’t understand that, it’s hard to push the boundaries of materials, process and speed. A key thing about 3D printing is that you can make the unmakeable, but you can also blend powders to create materials you couldn’t machine from a billet. So it’s not just about the printer, it’s about understanding the inputs.”

That focus on the material inputs ripples through every aspect of AmPro’s work. Its ambition is not just to make 3D printers, but to utilise additive manufacturing to develop technological solutions in an advanced production environment. So along with a range of printers, it produces a whole raft of supporting technologies aimed at optimising productivity and efficiency, while drawing on all the potential that additive manufacturing has to offer.

The company currently has three metal printers on the market: two single-laser models and a twin-laser version, with a smaller model due to be released by the end of the year. All AmPro’s printers are based around the selective laser melting (SLM) process, with parts produced layer-by-layer from a bed of metal powder.

“A key objective of the printer is to be one of the fastest printers on the market using the powder-bed process,” says Lele. “Another aspect is to keep that printer running all the time. If it’s not printing, you’re not making money. And a lot of printers have a significant amount of downtime, where you’re trying to dig out the part from the powder and removing build plates from the printer. That downtime requires an operator at a reasonable skill level, and it also stops your printer from printing the next part.”

To solve this problem, AmPro’s printers are equipped with a removable build chamber. Within minutes of finishing printing, the chamber can be decoupled from the printer and a new one can be inserted. The machine operator can immediately get the printer back up and running, while a less-skilled colleague can finish work on the printed part after it has been safely cooled in the removable chamber under inert environment.

“And that allows the part you’ve already printed to slowly cool down under an inert environment, same as in the printer,” adds Lele. “That’s all part of metallurgy and efficiency; you’re really trying to take the 3-4 hours or 1-2 days of cooling time away from your production whilst maintaining product quality. But this way, your printer is still going. So that’s a really important part of the system.”

A further key area of focus lies in the management of inert environments. Two of the primary materials that AmPro works with – titanium and aluminium alloys – are highly prone to oxidisation on exposure to air, which can inherently reduce the material’s properties and limit the number of times for the powder to be recycled. To prevent this, the interior of a laser printer’s build chamber will normally be flooded with inert gas during printing. However, this still leaves a lot of variables for manufacturers in some of the most demanding industries.

“Managing that process is actually a quality requirement for a lot of medical and aerospace products,” says Lele. “So we extend that right through, from the powder preparation right through to the last point at which you separate the part from the build substrate.”

This is where AmPro’s full product portfolio starts to deliver benefits. Prior to any printing taking place, the storage and preparation of powders is critical, and AmPro has developed technologies for materials to be decanted, blended, sieved and recycled, all in a controlled, inert environment, ready for use in the printer. At the other end of the process, a closed-loop powder recovery system means unused powder can be drawn out of the build chamber for recycling, while AmPro’s Residual Powder Removal equipment ensures any last traces can be removed, again while still in an inert environment.

As well as saving on material waste and machine downtime, this also brings occupational health & safety (OHS) benefits, given the hazards of working with metal powders; AmPro’s system means all those risks are contained, eliminating the need for safety masks or other measures.

Ultimately this amounts to a comprehensive ‘powder-to-part’ production system, which has interesting implications for industry. While there is a lot of excitement out there about additive manufacturing, there is also a considerable degree of scepticism within the industry. 3D printing is still widely seen as an exotic, expensive novelty, capable of doing amazing things, but difficult if not impossible to integrate into an efficient modern production line. AmPro is tackling those concerns head on, developing the most cost-effective process and the machines that can compete with more traditional manufacturing processes and existing machine suppliers, and thereby laying the ground for additive processes to really be adopted in production settings.

“The adoption requires a full understanding of the process, the requirements of aerospace and biomedical industry, and that’s been a really important dialogue with our customers,” says Lele. “It’s what really drove us to identify how to build a cheap, effective and efficient printing system. Our parts are very cost-competitive on the basis that we’re keeping it simple and easy to operate. We’ve really been very ruthless on what features ensure this can meet the needs of the broadest customer base, without all the bells and whistles, but that still meets expectations around quality and complexity.”

Aiming high

As it has embarked on bringing its products to market, AmPro has been specific in aiming at high-end, high-value-add manufacturing sectors. Given Professor Wu’s background in the industry, it comes as no surprise that aerospace has initially been earmarked as the primary target.

“That really drove a lot of our design decisions,” Lele explains. “We understood the requirements to get something on an aircraft. How do we meet those requirements in the engineering of a process to get it there? There’s a lot around the process and the laser strategy and the build strategy; all these little nuances. And unless you’ve done it, you kind of don’t understand the implications of it.”

Alongside aerospace, the medical sector has also been identified as an area offering significant potential, which has provided the impetus for the development of the smaller printer. A third key market is schools and academic bodies, as the challenges of designing products for additive manufacture create new specialised training requirements.

One key aspect of AmPro’s initial strategy in targeting the aerospace industry has been to focus primarily on the Tier One suppliers, rather than the Primes. The likes of Safran, Airbus and Boeing have got the financial resources to establish their own capabilities and processes. Those smaller manufacturers supplying them, however, have more limited budgets and are looking for ways to adopt these innovations more economically and incrementally – an area where AmPro can provide assistance. In this regard, having such a diverse range of products creates opportunities for AmPro to ‘get a foot in the door’.

“Quite a few people in industry who might have a printer already have seen our solutions and said ‘That’s a brilliant solution. Can we adapt it into our existing system?’ So AmPro has become this really unusual business where we provide either a printer and associated powder handling systems, a complete process, or our solutions have been ‘plug-and-played’ in units. It’s an interesting mix, the way the business has evolved.”

Given the industries it’s targeting, AmPro’s customers are almost entirely based overseas, with most clients in Europe and the US, as well as in China. The latter market is catered to by AmPro’s partner manufacturer in China. Other than that, however, the company’s products are manufactured by a team of around 14 engineers and designers at the Clayton worksite. According to Lele, maintaining a manufacturing base in Australia is important for AmPro, with the search already underway to find a larger facility as the business expands.

“Utilising all our suppliers locally, we’re drawing on some fantastic skills that we can’t actually get in China,” he says. “And we will be scaling up that manufacturing, mainly because we recognise the importance of quality coming out of Australia – the knowledge is good. Also, not every customer wants exactly the same thing, and we can actually accommodate nuanced changes here. So Melbourne’s always going to be our manufacturing base for a lot of our export markets.”

Indeed, the company’s Australian origins have proven to offer certain advantages, as shown at last year’s FormNext additive manufacturing exhibition in Frankfurt.

“One of the best compliments at FormNext was ‘I can tell this had been designed and engineered in Australia’,” Lele recalls. “We got that message daily; that classic idea that we solve complex problems with very simple solutions. So I think there’s a wonderful place for Australia in this. Our manufacturing here, utilising smart, efficient, but very simple approaches to solutions, will continue to allow us to grow.”

Breaking new ground

As a company that goes so far as to include the word ‘Innovations’ in its name, AmPro is intrinsically geared towards developing products at the absolute cutting edge of current technology. One factor that has been crucial in this has been its links with academic and research bodies. Founded to build on Xinhua Wu’s ground-breaking work, the company continues to work in close collaboration with the Professor and her colleagues at Monash, and for Lele this is essential.

“I couldn’t underestimate the value of being able to walk upstairs to 50 pre-eminent scientists in material science and say ‘Why does this do this?’, and have a discussion with them,” he says. “That’s been really critical for us. If we didn’t have that collaboration, having that understanding would be something we would have to build up, and it just takes too long. So collaboration is really critical in my mind.”

This collaborative approach is not just confined to academia either. AmPro works closely with its clients, adapting and updating its products continually to address specific problems that they need to overcome.

“You’ve got to work with industry. You need to go and spend time in a place, with a production worker, asking questions, learning first-hand and gathering insights. You need to get that insight in an emerging industry like this where you’re still finding your feet across a whole manufacturing system. You need to immerse yourself in it. And I love doing that because you build a relationship, and then you’ve actually got a customer because you’ve shown them a solution built on the insights of something that they can get a benefit from.”

This puts the company in an enviable position as additive manufacturing continues to evolve and mature, with ongoing technological breakthroughs opening the way for new potential applications.

“I think the applications will come usually through part complexity,” says Lele. “But it needs to start at the design. It’s not about someone saying ‘I’ve got this part we make using machining processes. Can we make it cheaper using additive manufacturing?’ That never works out. The real benefits come when you start looking at the full value chain of a product, and you actually say ‘This part might cost twice as much using additive manufacturing, but let’s think about what we’re holding in inventory.’ You can probably get four times a reward by removing inventory rather than by removing cost in a part. You need to look at it as a full value chain process. That for me is where the future was going in this area.”

Amid all this, Lele is bullish about AmPro’s future prospects: “We’ll be a very, very big company; I have absolutely no doubt about that. We’re growing at such a phenomenal rate. We’ve got international agreements already underway with the US and Europe. We’ve got distributor arrangements in place – they are already actively selling on our behalf.

“I see us growing massively here in Melbourne. And I think the company will always have the philosophy that what we started off with: that we just continue to do it better, faster, and smarter, and always challenge why we are doing it and how we are meeting the needs of the customer.”

www.amprogroup.com.au


Additive manufacturing in radiation dosimetry

Additive manufacturing (AM) enables the low-cost and patient-specific manufacture of anthropomorphic Radiation Dosimetry Phantoms (RDPs), used for the pre-treatment planning of cancer patients, to validate target doses and minimise the ionising radiation effects towards adjacent healthy tissues. By Rance Tino, Darpan Shidid, Bill Lozanovski, David Downing, Martin Leary, Tomas Kron and Milan Brandt of the RMIT Centre for Additive Manufacturing.

Radiotherapy aims to deliver a curable radiation dose to tumours while sparing surrounding healthy tissue, which is achieved by the accurate conformal delivery of ionising radiation via an external beam using linear accelerators, or an internal beam using sealed radiation source (called brachytherapy). Modern radiotherapy involves CT-simulation, 3D-treatment planning and its quality assurance processes prior to patient treatment to produce highly conformal dose distributions and to ensure its safe and accurate delivery.

It is common to build anthropomorphic RDPs through moulding and casting, to mimic the radiation properties of humans as a radiation dose cannot be directly measured in patients. As part of quality assurance (QA) of patient treatment plans, patient-specific dose measurements are often performed using RDPs combined with various dose measurement tools.

Unfortunately, anthropomorphic RDPs manufactured through traditional moulding and casting techniques are associated with high fabrication costs and long processing times. In addition to this, they are not patient-specific in terms of individual dimensions (particularly in respect to obese patients), feature standardised tissue heterogeneity, and lack pathological features.

This article discusses some of the basic concepts surrounding the manufacture of AM-RDPs, their clinical significance and requirements and their associated printing techniques and materials utilised at the RMIT Centre for Additive Manufacturing.

Anthropomorphic RDPs for treatment planning

The treatment planning procedure is a significant part of radiotherapy, whereby the optimal treatment parameters to be used for the management of a patient’s disease are determined. These treatment parameters include target volume, dose-limiting structures, treatment volume, dose prescription, dose fractionation, dose distribution, the positioning of the patient, treatment machine settings, adjuvant therapies.

The role of commercially available anthropomorphic RDPs is to act as a human proxy making it possible to experimentally visualise and evaluate treatment options tailored to the locality of patients. This importance signifies the current limitations of anthropomorphic phantoms as they only follow the average radiation and body dimensions of a ‘healthy’ person, with a lack of patient-specific pathological features – in particular, the mimicry of accurate lesion size and positioning. Therefore, research opportunities exist for AM technology in highlighting these limitations due to its conformal and rapid prototyping capabilities.

Patient-specific radiotherapy phantoms enabled by AM

AM provides opportunities for the inexpensive manufacture of patient-specific devices, as observed from the current literature not only for radiotherapy phantoms but also for other radiotherapy devices such as bolus, compensators, electron beam shielding, immobilisers, and brachytherapy moulds.

Novel AM workflows have been developed to accommodate imaging tissue-like heterogeneity utilising AM materials, via modification of infill parameters, doping, and the introduction of voided geometric features as the structural basis for AM-RDPs.

Types of AM radiotherapy phantoms

Early versions of additively manufactured radiotherapy phantoms were manufactured as shell phantoms, which are hollowed phantoms filled with various tissue-equivalent materials (such as sawdust, silicone gels, or cork). The emergence of better AM technologies has attracted interest in exploring the simulation of the human tissue heterogeneity, classified as as-printed phantoms.

Heterogeneity in printed phantoms can be achieved using modified material extrusion (fused deposition modelling (FDM)) printing parameters such as infilling patterns and percentage, printing nozzle size, temperature, and more recently, the modification of material extrusion rate using the Pixel-by-Pixel (PbP) method. Furthermore, contrast variations can also be achieved by constructing phantoms with two or more different AM materials (multiple material printing); doping filaments with high-density materials such as bismuth and barium sulphate to increase the observed HU range; and the use of controlled voided structures within the manufactured phantoms to precisely controlled HU values.

Recent studies have illustrated the combination of these manufactured phantoms with commercially available motion platforms and in-house motion devices to further simulate body movements, especially the thorax’s respiratory movements (classified as 4D-AM phantoms).

Clinical requirements and implications

Recently, printing guidelines and recommendations for manufacturing AM-radiotherapy devices have been developed by the SIG (Special Interest Group on 3D printing), a writing group representing the Radiological Society of North America. They are divided into four main processes including:

  1. Medical image acquisition – Commonly used imaging modality involves CT or MRI. Associated patient data should have sufficient spatial resolution to accurately represent anatomy to be modelled.
  2. Image data preparation and manipulation – This includes image segmentation, 3D CAD design, and file documentation.
  3. Generation of the 3D-printed model – This involves the printing process, post-processing, and model inspection.
  4. Quality Control program – This involves the delivery and discussion with referring physicians, pre-operative planning, material biocompatibility, cleaning and sterilisation, and clinical appropriateness.

Regarding printing materials, it is essential to consider the photoelectric and Compton effects when comparing result outputs with human tissues. Photoelectric effect serves as the dominant phenomena at low X-ray energies ranging below 200KeV, hence for imaging modalities (CT, MRI, PET). At higher X-ray energies up to 10MeV, Compton effects can be considered as the dominant phenomena, where material attenuation differs depending on their elemental composition, signifying how radiation doses are distributed. Ideally, additive manufactured RDPs aim to simulate not only the patient’s proportion and pathological features but also the imaging attenuation of human tissues, the photoelectric effect, the dose attenuation of tissues, and the Compton effect.

Also, for given printing material to be tissue or water-equivalent, it must have the same effective atomic number, number of electrons per gram, and mass density. However, since the Compton effect is the most predominant mode of interaction for MV photon beams in the clinical range, the necessary condition for water equivalence for such beams is the same electron density (number of electrons per cubic centimetre) as that of water.

AM playing with radiotherapy? Or radiotherapy playing with AM?

Despite the enabled low-cost and patient-specificity of AM radiotherapy phantoms, the associated printing techniques and materials are limited and are yet to be converged in terms of reproducibility, where manufacturability issues of current printing technologies are still present. FDM technology, in particular, is commonly used for manufacturing radiotherapy phantoms. This printing technique comes with inherent limitations in comparison with other printing techniques such as polymer jet printing and stereolithography (SLA), where observed void defects are observed, which in turn produces structurally weak and non-uniform dense objects.

Researchers at RMIT University are currently investigating the manufacturing process of these radiotherapy phantoms and exploring how they can be used in a clinical setting considering the required manufacturing compatibility, accuracy, time and cost. In highlighting previously mentioned manufacturing limitations, a unique geometrical structure called a ‘Gyroid’ is also being investigated by these researchers as they enable: controllable printing tool path parameters in minimising void defects; controllable porosity at all directions highlighting tissue-like heterogeneity and offering a similar tissue-like structure for assessing tissue deformability.

The RMIT Centre for Additive Manufacturing is involved in research projects with collaborators at the Peter MacCallum Cancer Centre, Melbourne, at Stryker South Pacific, St Vincent’s Hospital, UTS, IMCRC, DMTC, DSTG, QUT, University of Wollongong, Swinburne University, Ford and RUAG. This research is supported by the ARC Training Centre in Additive Biomanufacturing, which focuses on the research & development of new biomedical products using AM technology.

www.rmit.edu.au


How close are we really to 3D printing organs?

Additive manufacturing technologies are now so advanced they can create structures on a nanoscale. But how close are we to seeing 3D printed organs in the market? Professor Hala Zreiqat and Dr Peter Newman explain.

From cures for cancer to fusion power and driverless cars, almost every technology seems to be perpetually five to 10 years away. For researchers, “five to 10 years away” means we’ve been working on it for quite a while and it seems feasible, we just haven’t got there yet.

We understand people’s scepticism when we say “in five to 10 years we’ll be 3D printing organs”. Sceptical? Don’t believe us? Consider this: Over the last decade, there has been a paradigm shift in stem cell research.

Since the mid-1800s, researchers have been growing cells in sheets layered on top of glass and plastic dishes. This method is the cornerstone of biological research and its impact has been immeasurable – it’s responsible for the development of vaccines for polio, measles and smallpox, as well as the insulin that’s used daily by millions of diabetics worldwide.

That’s why it’s surprising that stem cell biologists have stopped using this method. Why? It’s simple: A sheet of cells layered over a dish doesn’t behave anything like the organs from which they’re derived.

The change in method is the paradigm shift we’re talking about, the one that means 3D-printed organs are knocking at the door.

Biologists have stopped growing cells in sheets layered over petri dishes and have started studying suspensions of three-dimensional organ-like cell masses, otherwise known organoids. If given the right biochemical cocktail, stem cells will proliferate into supercellular networks that spontaneously organise into three-dimensional structures that mimic the physiology of real organs.

The progress is staggering and multifaceted. Organoids promise to cut down on the need for animal testing and offer improved models to understanding disease progression. However, the study of organoids has offered unprecedented insights into the development of organs.

Producing organoids at a scale large enough to confer therapeutic benefit to humans remains a significant challenge. Large structures require supporting scaffold structures, such as the meshwork of collagens that stitch together the cells of your organs. However, recreating scaffold structures with sufficient detail to support the growth of large-scale cell structure has proven problematic.

Enter 3D printing.

The increase in life expectancy in Australia has improved dramatically in the last century with the expected age at death of 84.6 years for men and 87.3 years for women. This will lead to a significant increase in the need for organs to replace the damaged ones.

While biologists have been busy revolutionising cell culture methods, engineers have developed 3D printers that can focus light so tight, it can polymerise features similar in size to that of a single collagen molecule. This technology is known as multi-photon 3D printing and is the brainchild of Professor Martin Wegener.

As a pioneering user of this technology he’s demonstrated materials that can bend light around objects, effectively making them disappear. Yes, you read that correctly. He’s made an invisibility cloak.

Over the next five to 10 years we aim to use multiphoton printing to build synthetic scaffolds mimicking the meshwork of collagens that hold organs together. These will be sufficiently complex scaffolds which will support the growth of organoids large enough for clinical applications. This much at least seems feasible, but trust us, we’ve worked on it for a while.

Maybe it will be more than five, or even 10 years, before you’re stopping by the hospital to pick up a new heart, but you can bet that during this time we’ll be 3D printing organs.

Professor Hala Zreiqat is the Director of the Australian Research Centre for Innovative BioEngineering and the Head of the Tissue Engineering and Biomaterials Research Unit at the University of Sydney. Dr Peter Newman a research fellow at the ARC Training Centre for Innovative Bioengineering at the University of Sydney.

www.sydney.edu.au