In the past few years, 3D printing has caught the public’s imagination. However, like a magician’s hat, it has been limited to producing curios with little utility like plastic skulls with intricate patterns. Recently, 3D printing took a giant stride: the industry can now additively manufacture 3D objects from titanium. A metal valued for it high strength to weight ratio, titanium 3D printing could open new horizons in several industries.
The Technology that makes it Possible: Direct Metal Laser Sintering (DMLS)
Traditionally, 3D printing has relied on two technologies: stereolithography (SLA) in which a UV laser acts on a photopolymer to create the object layer by layer, and Selective Laser Sintering (SLS) in which a high power laser fuses the material in cross-sections outlined in the CAD file. Both these technologies work with simpler materials like plastic, ceramic, or glass and are obsolete when faced with a working material as strong as titanium.
3D printing with titanium has been made possible by a technology new to the digital manufacturing industry, called the Direct Metal Laser Sintering (DMLS). First, a computer aided design (CAD) of the part to be manufactured is created and fed to the machine. The laser acts on a homogenous and dense titanium powder that melts to create complex structures. Titanium 3D printers can attain precision and complexity in design that traditional CNC lathe machines are not capable of achieving. The machine operates in an inert gas (argon) environment. Different titanium 3D printers have different specifications but most of them build objects with a 30 micron layer thickness, allowing a minimum wall thickness of 0.3-0.4mm in the design. Some printers making titanium objects also use a technology called Electronic Beam Transfer (EBM) which is similar to DMLS but uses a beam of electrons in place of the laser.
What’s So Good About a Titanium 3D Printer Produced Object?
To be considered as a viable manufacturing option, a titanium 3D printer should offer value that goes beyond the current hype surrounding 3D printing. These printers pass this test with flying colors. Here is why 3D printing titanium parts is better than producing them using other manufacturing methods:
1 Greater Complexity and Resolution in Design: DMLS with titanium powder allows greater liberties with the CAD design. This includes deep groves, cooling channels in injection mold, cavities, undercuts and free form surfaces. The minimum wall thickness in DMLS using titanium is 0.3-0.4 mm, allowing incredibly detailed designs to be implemented. The produced parts can also be surface finished in a variety of ways.
2. Excellent Mechanical Properties: Titanium is a strong metal to start with. DMLS does an excellent job of preserving this strength during the manufacturing process. Instead of manufacturing multiple smaller parts before and joining them later, DMLS fuses every parts with the whole structure just as the laser creates it.
3. Accuracy in Production: Each part produced confirms to its sanctioned prototype. Typical achievable part accuracy is around +/- 50 microns.
4. Quick Turnaround Time: Depending on the size, parts can be produced in anywhere between a few hours to a few days. This ensures smooth production of the final product with any bottlenecks where final production is halted by availability of parts.
5. Re-design is Easier: If a part is re-designed, creating the newly tooled part is easy because only the CAD machine drawing of the part needs to be replaced. As such re-designing an existing part doesn’t bear a significant impact on the lead time.
Revolution in Titanium Powders for 3D Printing
Titanium has high strength to density ratio, and is corrosion resistant. It is biocompatible and has good bioadhesion and is hence useful in surgical implants. Titanium is also expensive; in 2002, titanium cost 17,000 per tonne as compared to carbon steel’s humble 550 per tonne. Traditionally, manufacturers have incurred significant losses by the titanium wasted during manufacturing. Titanium 3D printers rule these out by reducing wastage to a minimum.
A Rottherhan-based metal manufacturer, Metalysis has devised an innovative way of producing inexpensive titanium powder for 3D printers. The company performs electrolysis on rutile, directly obtaining powdered titanium for it in a continuous process. The morphology and structure of the produced titanium can be controlled in the process. Traditionally, titanium, has been produced by Kroll’s process which produces a porous block of the metal which must be powdered. The company estimates that the cost of powered titanium may come down to three fourths of what it is now. It is currently, planning to set up a powdered titanium plant at the cost of $50 million to $500 million.
Recent Applications of Titanium 3D Printing
3D printed titanium parts have been most enthusiastically received in the aviation industry. General Electric (GE) estimates that printed parts could bring down an aircraft’s weight by 1,000 pounds. GE is already printing fuel nozzles for its new CFM LEAP engines instead of welding each part from 18 smaller parts, as it did before. Airbus Group and EOS have designed 3D printed nacelle hinges in titanium that save 40% more fuel than their traditionally manufactured counterparts.
3D printed titanium parts have witnessed great success in the medical industry as well. A Chinese farmer’s damaged skull was restored with a 3D printed titanium mesh by the collaboration of Stryker, a medical tech firm and the Xijing hospital. Prosthetic cranial implants 3D printed in Trabecular Titanium have been successfully implanted in a patient in Argentina. Other applications include custom titanium shoes for a race horse in Australia. Hugo Arcier, an artist has created sculptures using 3D printing and displayed them in an exhibition called Dogma. Empire, a bike manufacturer tied up with additive manufacturing firm, Reinshaw to create a 3D printed titanium bike that has been subject of much talk.
Titanium 3D printers are quickly expanding into a profitable manufacturing niche. However, the industry has a few challenges to overcome. The first is bringing down the cost of titanium powder. The second is stopping titanium dust produced during printing from blocking small channels. Nevertheless, the industry can set its sights on conquering manufacturing drawbacks that inhibited use of titanium parts in a number of applications.