In the second blog of our series about gas in additive manufacturing (AM), we look at maintaining the optimum atmosphere – every time.
‘You’re only as good as your last game’. It’s a phrase you’re most likely to hear from the mouth of a sports pundit. But it’s a phrase that will ring true with additive manufacturers. The pressure is on to produce high-quality parts routinely.
But how? Well, there’s another concept that speaks to both sports folk and manufacturers: marginal gains. By breaking a process down into its parts, and making sure each one is working as well as it can, you get a significant increase in performance.
Ultimately, it’s about control across the whole process. In our first blog of this series, we looked at how to preserve powder quality. That’s great. But there is still a risk of porosity and variation during build, impacting the quality of the printed part.
Perfecting your printing
Just as you want the right conditions when you produce and store powder, you want to have precise control of the atmosphere in your build chamber. Even a tiny variation in the amount of air in the atmosphere can have an adverse affect on your end product. This is the result of the oxygen, nitrogen, traces of carbon dioxide, hydrogen and water vapour in the air. Trace amounts from small leaks or incomplete purges can cause impurities. This could discolour parts or make them more brittle.
In fact, air in the build chamber may be having a greater impact than we realise. Pierre Forêt manages the Linde research laboratory for additive manufacturing. He says, “The interplay between the atmosphere in the printing chamber and the final product is significantly more complex than many in the industry thought.”
Measure constantly. Control easily.
So, where are the tiny improvements in the build chamber that can make a big difference? First of all, how accurately can you measure humidity? At BOC, we have the technology to monitor and control oxygen as accurate as 10 ppm (parts per million) – without cross sensitivity. This technology is called ADDvance 02 Precision. You can choose the oxygen level that is suitable dependant on your part materials far more accurately than AM machines typically achieve.
Take titanium, for example. Often used in laser powder bed fusion, a technique for printing metals, it slowly reacts with the hydrogen in the air.
“Humid titanium powder behaves like wet flour, it coagulates and loses the ability to close its pores,” Forêt says. “If wet titanium powder is fed into a 3D printer, the printed product will inevitably be of lower quality.” Our gas technology gives you a controlled atmosphere to keep titanium and other metal powders at optimal conditions.
This level of accuracy makes a difference and helps you achieve the same results every time.
So, using ADDvance O2 Precision to purge your printer helps you to remove air – and keep it out. The technology keeps an over-pressure in the chamber. This stops the outside atmosphere from seeping into your printer. Plus, there are lots of other benefits; The nitrogen or argon gas removes fumes and splatter, controlling how quickly your melt pool cools a well as keeping laser lenses clean. Finally, if you work with reactive materials (like aluminium), they reduce the chance of an explosion.
Putting it all together
In the AM value chain, you can’t afford to have any weak links. A technology that gives you an accurate view of the conditions in your printer – and a precise way to control it – is therefore key to creating quality parts every time.
We help our customers use gas technology to enhance every stage of additive manufacturing.
Tanja Arunprasad, Linde Global Additive Manufacturing Expert
The next blog in our series will be about putting the finishing touches to your products. Keep an eye out for it.