When used together, 3D printing and topology optimization can deliver objects with minimum mass, which will save money in raw materials.
Topology optimization and additive manufacturing are two techniques that together have the potential to help you create a new generation of exciting products. While additive manufacturing, also known as 3D printing, is widely used by product development organizations to create prototypes from digital models, topology optimization has been restricted to companies with extensive CAE resources, such as automotive and aerospace manufacturers. Until recently, the tools needed to generate designs with organic-like structures had not been available at a price, or a level of usability, that encouraged broader industry adoption. But that is changing, and topology optimization and additive manufacturing are now poised to accelerate the process of product development.
The promise of marrying these techniques is not just theoretical. A number of organizations have demonstrated the benefits of combining additive layer manufacturing (ALM) with topology optimization design. For example, research at EADS has showed that an Airbus A320 hinge bracket could be significantly reduced in weight by using ALM in tandem with topology optimization. The optimization process enabled the designers to quickly hone in on the most efficient, lightweight structure, while the use of ALM created further weight reductions by minimizing waste in the manufacturing process. Using these techniques together, the EADS design engineers had greater freedom to explore alternatives while cutting overall development time and costs.
So what is topology optimization? It is a mathematical method that generates a material layout within a given design space based on a set of loads and other conditions provided by a design engineer. By way of example, let’s look at a simple beam created and optimized using topology optimization software solidThinking Inspire. In this case, the design space is a rectangular block, supported at the lower corners with a single load applied to the top face. Once the design space has been created and the loads applied, you run the optimization and within minutes, the software generates a result that looks like a structure one would find in nature. It is apparent that additive manufacturing technology is a more appropriate process for creating this structure than a traditional subtractive process like machining from a billet. The design freedom of additive manufacturing processes allows a literal interpretation of the design, saving weight while also reducing local stress and maintaining structural stiffness.
The Inspire software lets you sketch surfaces and create solids within an intuitive user interface or import data from your existing CAD tool. The geometry can then be prepared as a design space and materials and loading conditions assigned before being optimized. Although not always required for 3D printing, manufacturing and shape controls can be applied including minimum member size, symmetry, pattern repetition, or cyclic repetition. The results of the optimization can be exported in STL format.
Topology optimization results often have a visual appeal that provokes discussion. These conversations enhance the product development process by inviting early dialog about part loading, the product aesthetic, and manufacturing considerations. The optimization tool then enables you to quickly explore alternative directions, ensuring that you find a mass-efficient proposal. The opportunity to realize these results in a physical form through additive manufacturing increases the impact of the presented design concept.
The images of the chairs shows the rapid evolution of two of them designed using topology optimization and produced using 3D printing. The design space, shown in brown, represents the maximum volume that a solution can occupy. Typical loads for a chair and symmetry controls have also been applied. The optimized result is shown in orange. This result can be exported in STL format allowing minor updates to be made prior to prototype manufacture.
Now that additive manufacturing has removed many traditional constraints, the potential benefits of topology optimization are amplified. Saving product weight on a machined part does not necessarily save money. The size of the billet required is usually the same, but more material gets removed in the manufacturing process. With an additive technique, the amount of material used is directly proportional to the part weight: the heavier the part the more expensive it is to make. Now a part designed using topology optimization to achieve minimum mass will save money in raw materials. Our approach to product design should change as a result, especially when manufacturing small quantities of parts.
One historical challenge for engineers when presented with the results of topology optimization is translating organic-looking forms into CAD geometry ready for manufacture. While the manufacturing controls in the Inspire program make it easier to produce models suitable for conventional manufacturing processes, those who use 3D printing have the freedom to produce more complex shapes. The unconstrained topology results are invariably lighter than an interpreted version and save more time in the development process.
Faster, smarter, lighter
The Inspire software is not just suited to parts created using additive manufacturing processes. Stefan Terebesi Sr. Engineer at Key Safety Systems, Inc., a Tier 1 manufacturer of automotive safety equipment, has been using the software to help him and his team generate efficient structures for safety critical components in vehicle restraint systems. He explained, “We were interested in generating design concepts based on optimized performance requirements that would help design better performing parts in less time.”
The use of Inspire allowed the team to study quickly what effect changes to loading conditions or package space might have on their design direction. Said Terebesi, “solidThinking Inspire provides a tool that can quickly suggest ideal part geometries, giving an opportunity to reduce development cycle time and enhancing the knowledge of the engineer regarding structural requirements of the component.”
Additive manufacturing and topology optimization share many common attributes including the speed at which designs can be realized, the opportunity to quickly understand the effect of changes, and the delivery of the lightest weight solution. Using the two technologies together compounds these advantages.
While each has virtues when used independently, there is an enormous opportunity to combine them and multiply their advantages. MPF