Designing in 4D
Algorithmic Engineering of bi-metallic thermal actuators
Published 15 November 2021

Project Breakdown
Industry: Advanced Manufacturing
Product: Bi-metallic Thermal Actuators
Partner: Aerosint

The Vision

As humankind continues to boldly venture into space, modern technology is being tested under the most extreme of environments. Be it interplanetary missions or satellite operations, we are also relentlessly pushing the limits of reliability, lightweight and cost-effectiveness of the objects we launch into space.

When simple mechanical motions need to be repeated in a lightweight and cost-effective manner, compliant mechanisms are the go-to solutions. Unlike traditional rigid-body joints that are made out of several individually moving parts, compliant mechanisms are jointless or single-piece structures that achieve force and motion transmission through deformation and elasticity.

Besides being lightweight, reduced backlash, decreased wear and tear, and higher production efficiencies also count towards the numerous advantages of compliant mechanisms. To achieve desired deformations, these mechanisms are usually made of softer materials that bend and flex, but they do not function well under more extreme environmental conditions, such as the vacuum of space.

This dramatically limits their potential, especially in industries such as advanced manufacturing and aerospace, where metals are preferred for their mechanical and thermal properties. However, they are still heavy, with multiple components and limited in motion.

With the advent of Additive Manufacturing technologies like multi-material powder bed fusion, it is now possible to incorporate multiple thermal, mechanical or electrical properties within single-piece multi-metallic structures. Given the added design freedom, the challenge now resides with the engineers – how does one design a 3D-printed object, let alone a single-piece structure with multiple materials, that is meant to perform simple motions repeatedly?

This presented Hyperganic and our partner, Aerosint, with an opportunity to tap into the strengths of Algorithmic Engineering and dual-metal Laser Power Bed Fusion (LPBF) to accelerate the innovation of bimetallic 3D-printed compliant mechanisms – we envision a future where engineers can design with a new paradigm and selectively use materials to their strengths to achieve new combinations of complex properties and mechanical motions with single-piece objects.

Achieving the Vision with Algorithmic Engineering

Together with Aerosint, the Belgian printer manufacturer that pioneered Selective Powder Deposition, Hyperganic created a series of conformal bimetallic thermal actuators that perform specific motions under various thermal conditions.

These actuators work on the same principle that made bimetallic strips bend and curl. As we can now arrange the metals in desired patterns and structures, they can perform motions that are far more diverse and complex.

When supplied with thermal energy through electrical resistive heating, they are able to release payloads in space controllably through a clean motion. In the image below, the first two actuators from the left perform radial expansion motions and the last actuator performs a clamping motion.

With Hyperganic Core, a software platform for Algorithmic Engineering, we are able to algorithmically frame the engineering challenges while taking into consideration the properties and constraints associated with materials and printing technologies. Our collection of A.I.-based engineering tools then generates variations of objects based on physical rules that achieve target motions, be it expansion, twisting, clamping or more.

Bringing the bimetallic thermal actuators to life requires a printing technology that breaks the mold of traditional metal Additive Manufacturing. That is where Aerosint’s Selective Powder Deposition comes into play.

It is an alternative powder recoating system that, instead of uniformly spreading just one single powder material, selectively deposits two or more powders to form a single layer containing two materials.

Using an Aconity MIDI+ printer equipped with Aerosint’s recoater, the first of its kind available commercially, we printed the actuators in steel and copper alloys. This enables the actuators to have an effective combination of the high strength and corrosion resistance of stainless steel as well as the good thermal and electrical conductivity of copper alloys. Now geared with increased possibilities of target motions through Algorithmic Engineering and effective use of multiple metallic materials, the use cases for such objects are endless – from highly-integrated satellites to thermal systems and electrical circuits.

This is just the beginning of an era where Algorithmic Engineering and multi-metallic objects usher in a paradigm shift for engineers to rethink how they create objects and solutions to tackle pressing challenges. As more material pairs get validated for commercial use, applications for multi-metallic printing will diversify. Empowered by a software paradigm, it will become more impactful than ever, accelerating innovation and opening new doors for all.

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