Moving From 3D Printing to Additive Manufacturing

Scaling up to serial 3D printing production represents a huge opportunity for manufacturers. James Lawson talks to Materialise to find out how to take advantage of it. Steel 3DP component with metal-printed support structure used to hold the part securely during manufacture. The latest 3D printer technology often hogs the headlines – but the real...

Scaling up to serial 3D printing production represents a huge opportunity for manufacturers. James Lawson talks to Materialise to find out how to take advantage of it.

Steel 3DP component with metal-printed support structure used to hold the part securely during manufacture.

The latest 3D printer technology often hogs the headlines – but the real transformative power of 3D Printing (3DP) doesn’t come from simply building bigger and better machines.

Efficient serial production – true additive manufacturing (AM) – is the real game changer. Serial AM removes tooling from the industrial equation, slashing costs and lead times, improving product performance and making short runs of complex parts viable.

“Whether it’s porous medical implants, car bodywork or ski boot insoles, designs can evolve freely and quickly without traditional constraints,” says Phillip Hudson, managing director at Materialise UK.

“An iterative design process becomes the norm, shortening development cycles and encouraging greater innovation.”

Using AM, Airbus can quickly develop and revise small batches of ‘near net shape’ components that are lighter, require less subtractive machining, cost less and improve aircraft performance. If desired, each part can be slightly different too.

That mass customisation potential lets AM support entirely new business models impossible with conventional subtractive techniques. But successful serial AM remains a huge challenge for most companies. Misled by the ease of making single prototypes, many think they can just buy a printer and put it straight to work on the production line.

Taking that route is a recipe for disappointment at best. “We’ve found that achieving repeatable, efficient 3DP production with consistent quality requires optimising and tracking every single process,” says Hudson. “Many different threads must be woven together across software, hardware, materials and operations.”

Series production involves far more than just printing. To guarantee that the part you make today will be the same as the one produced next week or next year, you need to consider the whole value chain.

That chain starts with identifying the part to produce, then runs on through design, suitability for manufacturing, software, machines and materials, production process certification and post-processing.

Every single one of these stages has a significant effect on part quality and consistency, so the quality control process must be rigorous and well defined.

“With AM, the devil truly is in the detail,” says Hudson. “You have to understand all the nuances in order to produce exactly the same part every single time. Sure, manufacturers are familiar with setting up, organising and managing complex assets and processes. But those in AM are new, specialised and still changing fast.”

Creating designs together

Right at the start, you have to spot the component that best plays to AM’s strengths. Is it currently complicated or expensive to produce? Do you want to update the design frequently? Will the production volume be tens or hundreds?

Producing working components rather than visual prototypes means they must be structurally sound and identical from one year to the next. Those demands make the design stage more complicated.

“Our solution is co-creation,” says Hudson.

“For a viable AM design, you don’t just look at the CAD drawing in front of you,” says Fried Vancraen, Materialise founder and CEO. “You have to think about how the part will be used, the forces it will experience, how to minimise its weight, optimise its shape or how to combine multiple parts into one complex 3DP component.”

This is the process ATOS went through when it moved to AM production of titanium inserts for spacecraft. Typically used as mounting points, these components must have an enormous strength-to-weight ratio.

The cleverly optimised, lattice-structured AM version is just one-third of the previous version’s weight, and has better performance too.

Everything from layer direction to material density and heat treatment affect how parts like this perform. Just like injection moulding, there are many 3DP design rules and anyone designing for serial AM production must refer to all of them.

Unfortunately, engineers that know how to design for 3DP are still scarce and few UK manufacturers have yet to acquire the in-house skills needed to plan for and achieve serial AM. That lack of experience shows in all kinds of ways, like specifying a scrappage rate of five parts per million when your AM run only numbers hundreds.

“Our solution is co-creation,” says Hudson. “Manufacturers bring their product and market knowledge while suppliers bring 3DP software plus engineering and manufacturing know-how. Together, they can identify suitable applications, fine-tune designs to suit different 3DP technologies, test prototypes and move rapidly towards production.”

Obsessive about quality

With the design signed off, it’s then up to the factory to reliably reproduce all that preparatory work. “At the heart of quality control must lie a deep understanding of the 3DP process, with every detail of the design and product lifecycle being documented in line with ISO 9001 or more rigorous aerospace and medical QC standards,” says Jurgen Laudus, vice president of Materialise manufacturing.

Detailed reference data has to be stored for each part produced, covering everything from the source material and its thermal history to the end product’s material microstructure and mechanical properties. The same rigour applies to post-processing. Unique IDs enable this tracking and also help ensure that the right parts come together for assembly.

“The need for repeatability means every printer parameter and action has to be defined and controlled rigidly,” says Laudus. “The position and orientation of each part within the build, print head direction, machine calibration, how parts are removed, the test parts you create with each build and how you inspect them all have an influence.”

During printing, thermal sensors track the temperature of the laser melt pool and the part itself. Because new and used powders are mixed, continuous inline testing is needed to verify powder quality and every new batch of powder has to be traceable.

“Inspection and physical evaluations such as CT scans, tensile or fatigue tests are arguably more important in AM than in conventional processes,” says Laudus. “Where metals start as solid bar stock, the material supplier can guarantee their performance.”

“3DP is more akin to casting, with powders, resins or filaments which are only solidified into their final form during printing,” notes Vancraen. “3DP designs also often push the limits of structural strength in their quest for lightness and optimum shape, which is another reason to closely monitor material properties and consistency.”

Software for serial production

Software supports every stage of AM production, from creating stable 3DP designs to managing vast volumes of process sensor data. Serial production is impossible without it and translating an initial CAD drawing into a 3DP-ready file format is the critical first step.

“For the most part, prototypes simply need to reproduce a geometrical shape,” says Laudus. “End-use products must be structurally sound and stable as well as dimensionally correct.”

ATOS 3DP titanium spacecraft insert with post-printing machine surface.

3DP design software corrects CAD features like shared edges, open faces and gaps, helping the printer precisely reproduce the intended design.

It also aligns parts optimally within the build, checks for fit within the build envelope and predicts material consumption.

To cut down on manual design work, the software should automatically generate the support structures that keep components steady during a build. It’s essential to only produce just enough of them.

“They eat up material, slow down print times and take longer to remove,” says Vancraen. “There should be sufficient support to give a swift and stable print process while allowing easy removal post-print.”

Simulation is another vital stage in the AM value chain. High temperature gradients during metallic printing processes leave residual stresses in components. These can cause warping and shrinkage effects, leading to rupture or deformation during printing or distortions and micro cracks in the final part.

“By virtually testing proposed designs rather than prototyping, simulation software helps predict printing flaws instead of using trial and error,” explains Laudus. “This way, you can adapt the design and get to a repeatable output quickly.

As well as higher productivity and predictable mechanical performance, the saving from lower scrappage rates can be considerable.” Software’s other vital role lies in helping supervise AM processes.

Automatically recording process data and making it available for reporting and visualisation greatly simplifies monitoring and QC compliance. Automated part labeling and serialisation help track research, validation and production workflows for every component.

Data on everything from machine calibration, utilisation and scheduling to material deliveries and part inspection results supports continuous improvement and, of course, allows you to go back and check when there’s a problem.

Series manufacturing demands fine control of tool path and other printer features like calibration, something that machines don’t always offer as standard. Aftermarket software gives you full access to the printer to both tell it what to do and to export the data needed for process monitoring.

Print, then finish

3D printing alone is rarely sufficient to produce precisely the part you want. Metal components in particular require post-processing, often comprising 70% or more of the work involved in a fully finished part. That might mean milling or honing, surface finishing – bead blasting, polishing, painting – or heat treatments like hot isostatic pressing.

Metal components in particular require post-processing, often comprising 70% or more of the work involved in a fully finished part.

“One common medical component, a replacement hip joint, needs to be extremely strong while another, a cranial maxillofacial implant, has to bend a little to allow a precise fit and so must be slightly soft,” says Laudus.

“That means they need two completely different heat treatments.” All these processes and workflows must be mapped out, managed and monitored for precise repeatability.

“When we ship a part, the customer receives a written statement from us that it conforms to their specification,” notes Vancraen.

Achieving the same paint finish time after time demands fine control, from the applicator’s speed to the number of layers. But the final colour also depends on the printed surface texture so, once again, every part of the process has to be exactly as specified.

“Just like conventional machined casting production, the best way to guarantee efficiency and consistent quality is to put all services under one roof,” states Laudus. “We’re great believers in this kind of in-house production. This way, expert design and engineering support is available immediately for both 3DP and traditional processes.”

Most companies are used to producing large series of identical components whereas AM typically delivers lower numbers with enormous variety. Lower production volumes always pose organisational challenges and outsourcing only makes those harder to manage. To achieve extremely fast cycle times while maintaining repeatability and reliable quality control, you need to handle all the processes in-house.

Automation and additive manufacturing

Set up AM software correctly, feed it the right input parameters and it will automatically generate a one-off 3DP print file. When fed to the printer, it creates a unique component. “Last year Materialise helped produce over a million hearing aids and everyone was different,” says Vancraen.

For this kind of automated mass customisation, each component requires a separate pre-mapped design chain that starts with the customer’s measurements and preferences. These can be submitted via the web, allowing total automation from purchase to production. In contrast, AM post-processing is still largely manual, despite some mechanised techniques like batch drum sandblasting.

Multi-head, multi-purpose hybrid machines are now appearing that can print and then mill metal components, though these are still restricted to narrow applications. The set-up and part variation inherent in small runs is a challenge here, although a small series of similar components currently allows at least partial automation.

But if one day you’re making glasses and the next aerospace components, it’s not so straightforward. “The larger the production run, the more suitable it is for automation and the greater the potential cost reductions,” says Laudus. “In processes like colouring, where precise and consistent cycle times are needed, automation can often improve quality too.”

Grasp the opportunity

If you’re up for the challenge, serial 3D print production is a huge opportunity for UK manufacturing. It’s well out of the R&D phase and, though the technology keeps on improving, the materials, hardware and software are more than capable right now.

Making production line components is an excellent way to dip your toe in the water. “We work with UK car manufacturers who do just that as well as producing endues car parts in volume,” notes Hudson.

One European car manufacturer uses a combination of 3D-printed and off the-shelf parts to create a gluing jig that combines all previous components in one fixture, weighs 64% less and can be delivered in only two weeks at nearly half the price of the previous jig.

However, Hudson emphasises that thinking it’s easy to step from prototyping to serial production is the biggest fallacy in AM. “You can easily stumble and lose momentum or lose faith altogether,” he says.

“You really have to understand all the detail, from design through printing to post-processing, to make it a success.” Compared to prototyping, serial 3D print production is a very different kind of creature.

But in the same way that you don’t need to be an injection moulding specialist to use it in manufacturing, any open-minded manufacturer can make a success of AM. By working with the right partners, you can open the door to a whole new way of doing business.

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Source: www.themanufacturer.com