Pushing the boundaries
Additive manufacturing – the technical term for 3D printing – is becoming increasingly widespread in the processing of metal materials. The challenges here are much greater than with plastics processing, the first one being the source material. “Metal 3D mostly uses a metal powder, which is difficult to manufacture and has to meet very high quality standards,” Dr Bernd Hildebrandt, a Messer welding and cutting specialist, explains.
Powder bed and laser beam
Such metal powders come at a price. For 3D printing, they are first melted in portions, just like the plastics, but that is where the similarity between the processes ends. The first layer of the component is made from a thin layer of metal powder, which involves melting it using the heat generated by a guided laser or electron beam. The next layer of powder is then applied, which, again, is melted along the component contours. In this way, the desired product is produced layer by layer. Another additive process – powder spraying – is more reminiscent of welding. A carrier gas conveys the powder into a laser head, where it comes into contact with a laser beam and melts. The pressure of the gas moves the melt onto the workpiece, where it is given the desired shape by the computer-controlled movement of the head. This method can also be used to supplement and change existing components.
Even complex metal parts can be manufactured with a 3D process.
Additive processes take time. Depending on size, it can take hours or days to complete a component. “So far, therefore, 3D printing with metal has not exactly been a prime contender for mass production,” Dr Hildebrandt explains. “However, if we are talking about high-quality components with a complex geometry, then it is definitely worth considering. For example, you can produce turbine blades with intertwined cooling channels in a single operation, which would not have been possible with conventional processes.” In fact, besides the aircraft industry, power plant technology is one of the most important fields in which additive manufacturing is used. A well-known tyre manufacturer uses it to produce profile moulds for its HGV tyres. The process is also ideal for the manufacture of implants – tooth implants, artificial hip joints etc. – that are an exact fit for the patient’s anatomy.
The molten metal always needs to be protected against atmospheric influences, in particular oxidation. That is another similarity between additive manufacturing and welding. A publicly funded research project has confirmed how, in principle, different gases influence additive manufacturing with metals. “This is why we have created the ‘Addline’ product line. I expect the techno - logy to experience a boom in the near future, and we are prepared for it.”
DR BERND HILDEBRANDT
Senior Manager Application
Technology Welding & Cutting
Messer Group GmbH
Phone: +41 2151 7811-236
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