Additive Manufacturing ring for International Birthing Docking Mechanism (IBDM)

Additive Manufacturing ring for International Birthing Docking Mechanism (IBDM)

ESA Case Studies Additive Manufacturing ring for International Birthing Docking Mechanism (IBDM)

Primary Contact: Utkarsha Ankalkhope, Senior Research Engineer – Additive

Manufacturing: utkarsha.ankalkhope@the-mtc.org

Start Date: August 2017

Anticipated Completion Date: December 2018

Collaborators:

  • The Manufacturing Technology Centre (MTC)
  • Magna Parva
  • Cranfield University

The International Berthing and Docking Mechanism (IBDM) is the European docking mechanism compatible with the future International Space Station (ISS) US Orbital Segment (USOS) docking ports. The IBDM (original component shown in Figure 1) captures the vehicle flying to the ISS and it dampens the residual relative motion between the vehicle and the ISS. Once captured and dampened, the IBDM provides a structural pressurised connection between the vehicle and the ISS. The IBDM also allows berthing of a vehicle to a compatible ISS port by the ISS robotic manipulator.

The IBDM consists of the Soft Capture System (SCS) that captures the spacecraft and actively dampens relative motion and misalignment, and the Hard Capture System (HCS) that provides the structural connections and carries the service connections. This project aimed to demonstrate the added value of 3D printing by manufacturing a 1:1 model of the SCS ring integrated with the petals that are part of IBDM ring, by the Wire-Arc Additive Manufacturing (WAAM) process.

Figure 1 – IBDM SCS System (Images courtesy QinetiQ)

Introducing the roles of the partners involved in this project, Magna Parva established the product assurance requirements for space environment and monitored the product validation process of SCS ring; MTC is responsible for co-ordinating the design optimisation of SCS ring for the WAAM process, validation of design and the final machining of the part; and Cranfield University is responsible mainly for manufacturing of the SCS ring by WAAM process.

The main objective of this project is the redesign of the IBDM SCS ring to improve the overall performance in terms of reduced mass, manufacturing cost and delivery time with minimal impact on the environmental and mechanical performance. The titanium alloy Ti6Al4V was the selected material for this work (the original component was manufactured using aluminium alloy Al7075). The design optimisation task has been completed and it is in the final stages of getting design and drawings ready for manufacturing.

Cranfield University has finished the preliminary initial raw material and coupon testing covering tensile & hardness testing only (after stress relieving heat treatment and in as-built condition) and is currently working on optimising the manufacturing strategy for the trial representative ring sections, the 1/3rd of a ring and the full final ring. Figure 2, below, shows the outcome of the first of these tasks.

Figure 2 - Trial representative geometry; a) CAD of section, b) Section manufactured by WAAM, c) Tensile specimen extraction locations

The Manufacturing Readiness Review (MRR) took place in April’18, where the optimised design of IBDM ring by MTC and WAAM approach prepared by CRAN was reviewed by ESA technical team. Figure 3 shows the result of the design optimisation task and final CAD geometry through topology optimisation. A weight reduction of 15% has been achieved compared to the current design manufactured by traditional fabrication methods and mechanical joining. The ring and petals were designed as an integrated part, which illustrates an additional benefit of part consolidation by using AM along with weight reduction.

Figure 3 – Optimised geometry of SCS ring