3D printing: Layer by layer

9 December 2016

Faster, cheaper, less complicated: 3D printing offers many advantages compared to conventional production methods. In an interview with #explore, Jens Groffmann from TÜV NORD explains who benefits from additive manufacturing and why the technical testing group is committed to the cause of safety standards and norms in 3D printing.

What exactly is additive manufacturing?

Additive manufacturing makes it possible to dispense with moulds in the production of technical components from metals or plastics that it has until now been impossible to produce using conventional manufacturing techniques. Until now, components have been made from raw parts by removing superfluous material, for example through turning or milling. With additive manufacturing, it’s exactly the other way around: Nothing is taken away - instead, the product is built up layer by layer.

Do you have a specific example of this?

One good example is the shells of hearing aids produced using additive manufacturing. For this purpose the patient's auditory canal is measured, and a piece of plastic is then shaped to fit exactly into the ear. The strength of additive manufacturing, which is the rapid provision of individual parts, comes fully to the fore here.

How would you explain how 3D printing works to a layperson?

Like almost everything nowadays, the first step is taken in the mind of the designer. He visualises and designs a component using CAD software. The computer displays the object in three dimensions. In the next step, the designer transfers the virtual 3D model to a special data model, which can then be printed out in a 3D printer. During printing, the model is built up layer by layer from bottom to top...

... using laser technology?

That’s right. There are other procedures for plastics, but laser technology is the most interesting method for industrial applications. With what we call selective laser melting, very fine metal powder is applied layer by layer and melted in situ. The clever thing with this technique is that it does away with most of the restrictions you get with traditional technologies, and not only can components be optimised but certain ‘component geometries’ can also be produced for the first time which never used to be possible for technical reasons.

What other benefits do you see?

About ten years ago, large parts of the industrial production of various components, such as mounting fixtures or diecasting tools, were outsourced to China for cost reasons. The quality of production there is very good, but it takes 12 weeks for the container ship to reach Germany. And now you suddenly have the situation in which the designer no longer needs to send the CAD dataset to China but can instead get the workpiece printed in Germany. A few slight adjustments may be needed, but, depending on the scale and the number of pieces, the mechanical complexity remains very manageable. After two or three days, everything’s ready. The process of additive manufacturing will ensure within the next five years that the lion’s share of such industrial contracts will be awarded in Europe, simply because the method is faster and, when all is said and done, cheaper too.

TÜV NORD assures the quality of industrial 3D printing. Why does the sector need testing procedures?

Mainly because the technology is only just making its way from the laboratory stage into industrial production. This important process must be monitored by an independent testing service provider to guarantee quality in all areas - ranging from the materials used in the manufacturing processes to the properties that the finished component has to have at the end of the process. Is it exactly what the designer had in mind? The object might look just like the virtual model, but it could still have faults or, for instance, not meet the requirements in terms of strength.

Which testing methods does TÜV NORD use?

On the one hand, we test the materials and review whether the processes support safe production. On the other, we do of course go one step further and work with scientists to find answers to questions like how we design a stable manufacturing process, which parameters are particularly suitable for this, and how we deal with faults and breakdowns.

What’s your prediction - when will the first standard for additive manufacturing be in place?

My guess is that it will come in the next two or three years. TÜV NORD is proactively supporting this important process.