Skip to main content

A.dditive MA.nufacturing for T.iltrotor HO.using

Periodic Reporting for period 3 - AMATHO (A.dditive MA.nufacturing for T.iltrotor HO.using)

Reporting period: 2019-12-01 to 2021-05-31

problem/issue being addressed
The main objective of AMATHO is to develop and manufacture the housing of the main gearbox of the novel tiltrotor adopting the additive manufacturing technology. The project is challenging as component is very big (not feasible via AM at the time of the proposal) and critical for the safety of fly.
The development implies to evaluate main production processes (SLM, EBM, DLD) and metallic powders available on the market and to identify the parameters able to optimize the final component.
The assessment of precursor materials and manufacturing technologies, together with the development of proper “design for additive” approach will allow the adoption of Additive Manufacturing Technologies to manufacture large components, suitable to be installed on flying platforms, like tilt rotors.

important for society
Additive Manufacturing of metal components is a novel technology that, in principle, could substitute oldest machining and casting technologies. At the present state of the art, it is possible to manufacture components not feasible with other technologies, but AM can’t be adopted for massive production, due to time and costs constraints

overall objectives
The objective of project AMATHO is to develop a novel tiltrotor main drive system housing produced by additive manufacturing (AM) technology. Such a development process will include evaluation and choice of viable production processes and precursor materials; testing of coupons and intermediate proofs of concept for assessing static performance and fatigue endurance; design for manufacturing, definition of optimised manufacturing process, experimental testing and industrial engineering of an appropriate number of full scale housings to support flight clearance on NextGenCTR demonstrator. The adoption of suitable numerical tools for design, optimization and structural substantiation of the AM housing will constitute part of the project’s activities as well
Politecnico di Milano mainly focused on WP1 (Feasibility Study & Preliminary Design), WP2 (Material Characterization):
WP1, aimed to identify the most suitable metal Additive Manufacturing (AM) process, material and design strategy for critical aerospace component manufacturing has been concluded.
The POLIMI team explored both Powder Bed Fusion (PBF) and Directed Energy Deposition (DED) techniques (Figure 1). Three suitable AM methods were individuated in the two different classes, including:
- Selective Laser Melting (SLM)
- Electron Beam Melting (EBM)
- Laser Metal Deposition (LMD)
Furthermore, a review of currently available metal AM systems was performed, analysing features and performances of each of the off-the-shelf system
The aluminium alloy selected and considered in this project is A357 (Al-7Si-Mg). A357 alloy is relatively easy to process by SLM and LMD (compared to other aluminium alloys) thanks to its good fluidity in the molten state and to the small difference between its liquidus and solidus temperatures, however it is not processable by EBM.
Ti6Al4V is the most widely used titanium alloy. It features good machinability and excellent mechanical properties. The Ti6Al4V alloy yields high performances for a variety of weight reduction applications in aerospace, automotive and marine equipment. For this reason, it was selected within this project.

WP2, aimed to identify mechanical properties of components manufactured with AM, started the coupons manufacturing and their testing. The work is in progress, according to the plan.
WP2 is focused on process/material and it is 41 months long. WP2 is composed by four tasks, where task T2.1 is focused on the material/process investigation and characterization; task T2.2 on the prototyping of PoC and task T2.3 on the definition of design for AM rules, while task 2.4 is the joint concept review.
WP2 started with the manufacturing of ASTM specimens according to the outcomes of WP1 and the mechanical characterization of these specimens is in progress (T2.1) while PoC prototyping (T2.2) and definition of design rules (T2.3) are in the ramp-up phase.

At the beginning of 2018, also WP3 (Detailed Design and Process Development) started, with the collaboration of all three consortium components.
The main objective of WP3 is to develop research activities in order to bridge the gap between the capability expertise on AM technologies gained in WP2 and the novel AM system for large components to be built in WP4. WP3 is specifically organized in three tasks:
1) T3.1 Design and structural optimization
2) T3.2 – Process Development – which is the task where all the modules of the novel AM system are defined, designed and tested
3) T3.3 Methodologies for design, optimization, structural substantiation of AM parts
Activities carried out in WP3 are all in-line with the expected timeline. Most of the activities in T3.1 and T3.2 have been designed to act in parallel, using several intermediate meetings to share all the information along the way. Most of the experimental activities in T3.1 and T3.2 have been carried out on two similar AM systems, one installed in SUPSI and the second one installed in PRIMA. In particular, all the experimental activities in T3.1 have been carried out on a prototyped system which is a rescaled version of the one that is under development in PRIMA in T3.2 (1 KW instead of 3 KW, 5 instead of 7 axis). This allows us to undertake all the experimental issues that are not scale-dependent (material processability, complex features printing, defects detection/reduction) before moving to the full-scale setting. On the other side, Task 3.2 is taking care of all the issues which are scale-dependent, which is one of the main goals of the AMATHO project.

During P3, WP1 was no more active, while WP2 and WP3 have been the key technical WPs for this contractual period: 100% of Aluminium and 100% of Titanium coupons have been manufactured, while most of them have been tested.

Activities in WP3 have been focusing on designing and developing the novel DED system targeted to produce large scale AM components in Ti-6Al-4V alloy. Most of the activities have been focusing on designing the new system architecture, the laser source and powder deposition system, investigating the appropriate strategy for effective and efficient printing and developing novel solutions for monitoring and control the process for the large-scale target.

During the whole period the Topic Leader has been frequently met by the Consortium, with formal and informal meetings
Although the P1 was typically preparatory to the subsequent research, important results have been obtained with regard to the characterization of the precursor materials, in particular with respect to the characteristic that is called "fluence", described in detail by the article "On the Pulsed Selective Laser Melting Fluence parameter " published in 2017 by the "International Journal of Advanced Manufacturing Technology"
P2 and P3 increased Partners knowledge relevant to the AM melting process and the real time evaluation of the melt pool: the deep understanding of the melting process has been trensferred on the DED machine in WP4
Manifold manufactured in EBM-Ti
AM manufacturing strategy of ASTM specimens
Aluminum ASTM specimens manufactured with SLM