Meltio metal 3D printer tested for titanium implants

As part of the ATILA project, Spanish research center AIDIMME recently installed a metal 3D printer prototype from Meltio to prototype manufacture biomedical implants made of titanium alloys

ATILA researchers are studying and developing a high protection additive manufacturing process using direct deposition of metal by wire using multi-lasers for the processing of highly reactive materials.

The project is formed by a multidisciplinary consortium led by AIDIMME, with participants including Meltio, the Research Foundation of the General University Hospital of Valencia (FIHGUV), and the Laser Applications and Photonics research group of the University of Salamanca (ALF-USAL). It is funded by the Valencia State Research Agency, Spanish Ministry of Science and Innovation, and the European Union.

What is welding wire direct metal laser deposition?

ATILA is investigating the manufacturing and applications of biomedical implants made from Ti64-ELI titanium using welding wire 3D printing.

Meltio said unlike other additive manufacturing technologies such as laser sintering - a metal powder 3D printing method including laser powder bed fusion (PBF-LB/M) and electron beam powder bed fusion (PBF-EB/M) - welding wire 3D printing is more efficient, with less polluting processes that generate less material waste in its handling, which can help improve sustainability to reduce the carbon footprint of this technology.

Mario Martinez and Fernando Molinero operate a Meltio metal 3D printer. Source: Meltio

The direct metal laser deposition (DED-LB/M) additive manufacturing process can fabricate parts with the addition of raw material in the form of powder or wire. The advantages of DED-LB/M technology using wire, the company said, include lower process contamination than when using powder, good deposition rate, relatively low cost, and high raw material utilization close to 100%. Although powders can be reused, their chemical composition must be controlled and varies after each use.

Shield gas keeps oxygen content within standards

During an additive manufacturing process, highly reactive materials such as titanium have a tendency to pick up oxygen from the air due to the increase in temperature during melting and subsequent deposition of successive layers.

For biomedical implant manufacturing, the oxygen content must not exceed the maximum limit established in the reference standards for implants, including UNE-EN ISO 5832-3:2017, which covers surgical implants made from wrought alloy based on titanium, aluminum 6, and vanadium 4.

The maximum oxygen value allowed is 0.2% for Ti6Al4V grade 5 and 0.13% for Ti6Al4V ELI, a stricter oxygen limit in reference standard ASTM F136-21.

Meltio said the use of shielding gas coaxial to the melt is characteristic of DED technology. Meltio's metal 3D printers melt solid metal material, creating parts layer by layer to ensure high material deposition efficiency and print quality.

ATILA researches geometric limitations of DED-LB/M

ATILA Project consortium’s management team said development of DED-LB/M can help assure the quality of implants by producing preforms close to the final products, which can limit the amount of waste compared to traditional machining down of a metal block.

Research during 2024 into the DED-LB/M aimed to build “advantages in the function” upon powder-based titanium implant additive manufacturing, with factors including high capacity of adaptation to patients and creation of three-dimensional structures that favor the growth of the bone.

During 2024, ATILA researchers made progress in several aspects within its main objective of manufacturing biomedical implants that comply with regulations:

Source: Meltio

• A study was carried out to determine the geometric limitations of the DED-LB/M process when manufacturing parts with different complexities, such as different degrees of inclination or cylinders with small diameters up to 3 millimeters. The maximum possible angle of inclination to be manufactured without sagging was found, as well as the minimum diameter to be manufactured when using a 1 millimeter diameter Ti6Al4V wire.

Source: Meltio

• A thermal camera was used to carry out thermographic controls for each manufacturing process by measuring temperature at a specific point of each deposited layer in order to verify microstructural and chemical composition characteristics.

ATILA said analysis of the information it has acquired will help address problems related to oxygen uptake during manufacturing in order to meet health sector regulations and standards.

FIHGUV supplies implant CAD files to AIDIMME

The ATILA project involves studying the feasibility of manufacturing different biomedical implants, including:

• Stemless cage for bone graft (for shoulder)
• Distal radius plate (for forearm area)
• Cranial implant without screw system (for the skull)
• Acetabular implant (for the hip)

Source: Meltio

FIHGUV has supplied the required stereolithography (STL) computer-aided design (CAD) files for the implants to AIDIMME, where they have been modified in their geometry to adapt them to what is possible to manufacture with the DED-LB/M technology, including necessary roundings.

Future in vivo, in vitro tests, digital twin development

At present, Ti6Al4V blocks in grades 5 and 23 have been fabricated into samples for mechanical tests and microstructural characterization, as well as heat treatments as required. In the coming months of 2025, ATILA plans to complete the characterization and verification testing process and implants will be fabricated for the first in vitro (laboratory) and in vivo (inside a living organism) tests by FIHGUV.

Due to the required level of precision, preforms of implants manufactured, such as this distal radius plate and acetabular implant, will have to be machined before their use.
Source: Meltio

As part of the ATILA Project Dissemination plan, Meltio presented a webinar to showcase the ATILA prototype; chemical, thermal and microstructural characterization carried out to date; manufactured demonstrators; and the future challenges of the ATILA Project.

At USAL, a digital twin of the new titanium 3D printing prototype is being developed together with AIDIMME and Meltio using laser welding wire technology, where researchers are studying nanostructuring using ultrashort pulse lasers for the improvement of biomedical implants.