Siemens Mobility opened its first digital rail maintenance centre – the Siemens Mobility RRX Rail Service Center, in Dortmund-Eving, Germany, in September. The new maintenance depot has invested in a Stratasys Fortus 450mc Production 3D Printer to produce replacement parts and tooling on demand.
With the machine, Siemens Mobility has eliminated the need for inventory of selected spare parts, reduced the manufacturing time of these parts by up to 95% and can use it to respond to all internal and customer demands seamlessly.
“Bringing together a range of innovative digital technologies, we can significantly increase the efficiency of our customer’s rail operations,” says Michael Kuczmik, head of additive manufacturing at Siemens Mobility, customer service. “Stratasys additive manufacturing plays an integral role, enabling us to optimise spare parts for longer life cycles, at reduced cost and in shorter timeframes than ever before.”
According to Kuczmik, the ability to 3D print customised replacement parts on demand has increased its flexibility to meet customer requirements. Previously, Siemens would rely on traditional methods such as casting to meet customer demands, but this required long lead times. To make it cost-effective, the team would often cast large volumes, which resulted in lots of unused parts.
“Parts that took six weeks, can now be produced in 13 hours. Within a week, we can iterate and optimise the design and then 3D print a final, customised production-grade part,” adds Tina Eufinger, business development, additive manufacturing at Siemens Mobility Division.
It is clear that being able to 3D print customised replacement parts on demand has given Siemens a new solution to cutting time and costs for one-off parts. But can this success be replicated by any operations engineer tasked with replacing hard-to-find components? Could 3D printing really pave the way in the war on obsolescence?
3D printing technologies work whereby parts are built layer by layer. Eric Bredin, vice-president of marketing, EMEA, at Stratasys, explains that the 3D printing equipment setup needed would depend on the “complexity and functionality” of the part.
It also depends on whether the original computer-aided design (CAD) file of the part is still available because it is required to print the part. If it doesn’t exist, then a digital 3D model will have to be made from scratch, or reverse-engineered from a spare parts using a 3D scanner.
Often, the part required will not have been designed with 3D printing or additive manufacturing in mind. “In these cases, it is often more valuable to redesign it, or scan and optimise the file for 3D printing,” Bredin explains.
“A redesign can offer any number of benefits, from creating a part that is more flexible or light-weight, to customising it to the needs of a specific user. In turn, this can offer users a reduction in both time and cost.”
When it comes to the choice of optical scanning technology, Thorsten Brecht, senior director of product design at Faro, says that there is no simple answer. Scanners vary in their ability to capture.
Small parts, up to 150 mm in each dimension, can be measured with computed tomography (CT) technology. The possible size of the part that can be scanned is also dependent on the material and overall wall thickness. CT enables also enables the user to get a 3D point cloud of the entire part (not just the surface, but also the interior) without the need to disassemble the part. This kind of scanner can reach accuracies between 10-30 micrometres.
“If the inner structure is not of interest, parts of a similar size and even up to maybe 500 mm in each dimension, then imager products can be used to capture the outer surface of a part,” explains Brecht. These technologies project a pattern of different stripes onto the part that is captured by two cameras. Using triangulation, a point cloud of the outer surface of a part can be calculated.
“For larger parts to be scanned, a ScanArm is the best technology to use. The Laser Line Probe attached to it can scan up to 600,000 points per second. For larger objects like a car, a truck, a boat or even an aircraft where high accuracy is not needed, 3D handheld scanners and/or laser scanners are the best choice.” Handheld scanners enable the user to be mobile.
Brecht is also keen to point out that the actual 3D scanning of an object is just one step of a larger process. For a 3D printing application for example, a so-called ‘watertight mesh’ is needed as an output. This means that the point cloud created by the 3D scanning needs to progress through the following steps:
● Registering individual scans/point clouds
● Optimising the point cloud (usually supported by wizards and default settings of the software)
● Mesh generating – the points of a point cloud are basically linked together to form triangles that generate a polygonal surface
● Optiming the mesh (usually supported by wizards and default settings of the software)
● Closing all holes in the mesh to get a watertight mesh that is needed for 3D printing (usually supported by wizards and default settings of the software)
● Tweaking the design slightly before printing (for example, changing it from a solid part to a hollow part at the lower extremities, saving material when printing).
As 3D printing has advanced, so too have the materials that manufacturers are experimenting with. ABS plastic, poly-lactic acid (PLA), polyamide (nylon), glass-filled polyamide, stereolithography materials (epoxy resins), titanium, steel, wax, photopolymers and polycarbonate are just a few examples of the materials now available.
One real-world example includes the ‘hermit crab’ television advert for UK property website Zoopla (https://is.gd/dozido) where special effects company Artem used technology from Stratasys to 3D print shells topped with houses out of Stratasys’ ABS plastic materials.
Another example involves a Sheffield knife maker teaming up with the Advanced Manufacturing Research Centre (AMRC) (https://is.gd/balewu). Stuart Mitchell Knives and the AMRC carried out a project to produce a titanium chef’s knife, comparing it with traditional methods. This resulted in a “quality” piece, but it did, however, need a degree of grinding to apply an actual cutting edge.
Materials are also being developed to survive in certain scenarios and environments. Bredin explains that material development is a constant activity at Stratasys, with engineers working towards higher chemical resistance for fuel exposure and optimal combinations of toughness, ductility and stiffness for durability.
“New materials, such as our recently-introduced carbon fibre-reinforced nylon 12, are opening new applications that were previously impossible. 3D printing composite materials like this provides the strength of metal, with the light weight of plastic,” he says. “Another good example is the high-performance Antero 800NA, which offers high chemical resistance, meaning it can be used for components exposed to hydrocarbons, such as fuels, lubricants and many acids. Its low outgassing allows it to be used in confined spaces and sensitive environments. Meanwhile, other customers are taking 3D printed parts into space and onto the Formula 1 race track.”
Skills and expertise
The expertise and knowledge needed to run a 3D printer can vary based on complexity of the part and its use case, say Bredin at Stratasys. “A basic shape and volume can be designed or scanned within minutes, with very minimal training,” he explains. “However, in the industries in which we operate, the reality is that in most cases, a greater design complexity is required.”
Brecht says that the skills required for scanning also vary on the kind of technology being used. “X-ray technology needs special safety instructions and training before such a scanner can be operated,” he explains. “Most other 3D scanning solutions need one or two days of training to learn the basic set-up and tips and tricks for best practices based on the specific applications.” For some scanners it is also sufficient to watch a video tutorial online.
Bredin adds that in the past it was easy to make mistakes in 3D printing, as multiple steps were required to generate a clean, ready-to-print 3D file with no errors. If an issue was only noticed during the build-checking process, then the design phase would have to be repeated and a clean file created. “There are, of course, elements in which advanced training is essential. In the case of full-colour, multi-material 3D printing when graphic design skills and CAD knowledge are combined, we offer a full service of 3D printing expertise.”
Two words that are on the lips of the entire workforce – from engineer to management – when it comes to a new way of working or solution is ‘time’ and ‘cost’. Everyone is looking for that next solution that can save time and cut costs, instead of increasing them.
Chuck Hull, co-founder and chief technology officer at 3D Systems, which is supporting the U.S. Air Force in its effort to reduce production costs and delivery times with additive manufacturing technology (see box), says that additive manufacturing is the “perfect lean solution” because it “avoids the need for time-consuming and costly tooling”.
Brecht, meanwhile, says that the cost of implementing scanning equipment can range from an entry-level solution that starts at less than €3,000 to a high-end solution at more than €100,000.
Bredin echoes that “there is no generic answer” to how viable 3D printing parts is, both financially and time-wise, because if you compare the cost and time ratio of producing a part with 3D printing to conventional methods, you are always comparing a multi-step process with a more ‘single’ step process.
“For example, 3D printing a part may be slower than using injection moulding, but when you consider the time required to produce a mould and the associated cost, it’s easy to create a positive cost comparison for a series of parts that can be counted by hundreds or thousands,” he explains. “There are always lots of factors to consider, such as the size of the part, the complex geometries required, the number of tools required, the printing time needed [and more]. The result of the above is a complex calculation that will also vary depending on the technology used.”
Bredin concludes: “In terms of cost, there is a very wide range here. This is dependent on the expected applications and capacity requirements. Without understanding if the needs of the project are one part, 50 parts or a hundred parts, it is difficult to draw a generic cost assessment.”
It is clear that 3D printing is giving many in industry the opportunity to address the problem of replacing hard-to-find parts. However, to make a real success of this technology, engineers need to ensure that they understand the different types of systems available to them and the extra work that may be needed if the original CAD file isn’t available. Knowledge on what material type would work best on certain components, extra training needs required to use 3D printing technology and the overall cost of implementing such a system also needs to be taken seriously.
BOX OUT: U.S. Air Force keeps old planes flying with 3D Systems
3D Systems’ Figure 4 Production system has been selected for U.S. Air Force-sponsored research that is focused on integrating high-speed 3D printing into the aircraft maintenance supply chain.
Through the project, the U.S. Air Force will explore how the Figure 4 Production system can be used to reproduce aircraft components for decades-old planes that may no longer have reliable sources of replacement parts. Legacy aircraft require parts that may be out of production due to manufacturing obsolescence, low-quantity requirements, poor documentation, or other availability-related challenges.
The project will, therefore, aim to demonstrate capabilities for rapidly delivering replacement parts just-in-time without minimum order quantities – eliminating the need for warehousing and reducing time aircraft downtime. It marks the first time the U.S. Air Force will deploy so-called Digital Light Processing (DLP) technology to supply components, including electrical connectors, knobs, elastomeric grommets, and spacers.
The project is overseen by America Makes and led by the University of Dayton Research Institute (UDRI), bringing together 3D printing and aerospace manufacturing leaders, including 3D Systems, Lockheed Martin, Orbital ATK and Northrop Grumman.