Dassault Systèmes has made good on its SOLIDWORKS World 2017 promise to include topology optimization within the SOLIDWORKS Simulation framework.
Original part (left) compared to a topology-optimized part (right). (Image courtesy of Dassault Systèmes.)
Topology optimization is one of the biggest additions to SOLIDWORKS Simulation 2018. It takes minimal inputs from a user(loads, design space, constraints, boundary conditions and manufacturing methods) and then runs an iterative algorithm that supplies a near-optimized part.
No doubt a tool like this would be useful to many users from nearly any industry, so let’s dig deeper into how it works and what it does. For a quick overview, check out this video:
For more on what is new in SOLIDWORKS Simulation 2018, besides topology optimization that is, read this article on Engineers Rule (click here).
How SOLIDWORKS’ Topology Optimization Works?
So, topology optimization must sound magical to many design engineers. It seems to do most of the thinking for you.
Some topology optimization tools grow parts from scratch. Others chisels away at an old design until a new optimum is revealed.
In other words, topology optimization can be an additive or subtractive algorithm.
For SOLIDWORKS, they chose to focus on the subtractive method. To achieve this, they used the Tosca optimization engine under the hood to power the optimization.
“We felt the subtractive method was most attractive to our customers. It’s good with existing geometry you want to refine,” said Stephen Endersby, director of product portfolio management at SOLIDWORKS. “With Tosca, we also have the technology that has a track record in-house. So, it was a good, safe solution for our users.”
The software works by turning a design space into a mesh and then subjecting it to a simulation complete with user-defined loads, constraints and boundary conditions. The software then looks at the stiffness of each individual element and cuts out elements that appear to offer little to no structural or manufacturing benefit. This process is then iterated until the part meets all constraints and global compliance.
“Global compliance defines the stiffness of the component,” explained Endersby. “The software looks at the original shape and how the shape will deform under the loads. The software then compares these values to measure a deviation. You want to minimize the overall deflection.”
The cut-off point for each element can be user defined and altered at any time. This tells the software when to keep or eliminate an element. The system then recalculates the next iteration without these elements and sees if the part now exceeds or is within target of the global stiffness.
Users can also set manufacturing constraints that limit the changes to the geometry. For instance, engineers can define axes of symmetries, thickness controls, handedness, mold direction and more. These tools will help to ensure that your part will still be manufacturable despite its organic look.
As an example, the mold direction will notify the topology optimization tool of the direction the part will be pulled from. This will help to limit cavities, undercuts and parts that are impossible to extract from molds.
How to Use SOLIDWORKS Topology Optimization
To start the topology optimization process, a user defines the loads, constraints and boundary conditions of a part. From there, they must define the goals of the topology optimization.
Currently, the goals compatible with the topology optimize include optimizing:
- Stiffness to weight
- Minimal mass
- Maximum displacement
Constraints on the optimization process include:
- Required mechanical copies
- Percentage of mass removed
- Manufacturing process
- Maximum deflection
It should be noted that only one of these goals can be chosen at a time. Endersby suggests to start with stiffness to weight.
“It’s a good starting point,” said Endersby.“Everything will match up in a nice way with respect to the inputs, boundary conditions and strengths you apply. This is a benchmark. No analysis is a one-shot deal anyway. First, make assessments and see what happens when you change the topology optimization approach. Topology optimization can look at multiple criteria and loading conditions. The best thing is to create multiple studies with different goals to get what you want to do.”
Endersby suggests that engineers use the topology optimization tool to test out the extreme situations. You want to discover how far you can really push the design. To that end, the product comes with a load manager to keep track of the load inputs that will govern the outcome of the part’s topology optimization.
Endersby even hints that future versions of the topology optimization tool might keep track and manage your goals, constraints and manufacturing methods. This will help to speed up the development of your part and reduce any unnecessary rework. In theory, this could even streamline or automate the design space exploration. This tool would be similar in function to the load manager.
A constraints manager tool will be very useful to future iterations of the topology optimization tool. It will help engineers to optimize the trade-offs they will invariably find. Tools like this will help engineers see that “some constraints can be relaxed, while others can not—they will know the limits of their design,” said Endersby.
Users are also able to exclude regions of their part from their topology optimization. There are various reasons why this would make sense. Perhaps it is a region that holds onto a bolt? Perhaps it is a face that connects to another component? Perhaps it is a face that completes a seal with another component?
In this case, Endersby again suggests to run multiple runs to see what happens when you preserve the region and what happens when you don’t. This might inspire your team to better design the overall assembly.
“For all analysis, even topology optimization, you never hit run once,” said Endersby. “You look at the results and run it again with different assumptions and inputs to evaluate those inputs. Then you run it again. It’s an iterative process.”
How to Turn Your Topology Optimization Into CAD
One advantage to SOLIDWORKS’ topology optimization tool is that it is designed to take these designs into a CAD environment.
Endersby explains that there are three methods to bring your optimization into CAD for further analysis and processing.
First, you can display the results on top of the original CAD model that spawned the optimization. The engineer can then use this overlay to guide the changes to the original geometry.
Second, engineers can save their topology optimization geometry into an STL file. Because there is a new ability to work with mesh bodies in SOLIDWORKS, this effectively brings the geometry into your CAD.
From here, the engineer can use the “calculate smooth mesh” function to get their geometry.
Finally, there are various partner products available to users that will surface wrap your geometry.
This will help engineers to keep the organic look of their optimizations while simultaneously cleaning up the geometry. One such surfacing add-in available to SOLIDWORKS users is NPower.
The Future of SOLIDWORKS’ Topology Optimization Tool
A drawback to the SOLIDWORKS topology optimization tool is that it currently lacks a strength-to-weight ratio topology optimization. Endersby notes that this is something we should expect to see in future releases. After all, it’s one thing to optimize your part stiffness so it doesn’t bend, but you also don’t want it to shatter.
“When we originally started designing the topology optimization engine,we were working on strength-to-weight ratio,” admitted Endersby. “We moved to stiffness-to-weight ratio because it was more accurate to what the solver was giving you in the first iteration. Plan on bringing in strength to weight.”
Another addition Endersby hopes to see added to the tool is the optimization of components within an assembly. Currently, loads from the assembly are imprinted on the part using motion analysis and assigning calculated loads onto regions of the part using contact forces.
Finally, Endersby is hoping to bring more multiphysics into the topology analysis. For instance, modal, thermal and buckling are all on his list.
As Endersby said, “We don’t want this to just be demo candy. We want people to use this in real life.”
To be used in real life, the topology optimization tool must model real life and therefore account for multiphysics. “There are more constraints in the real world than this first release,” agreed Endersby. “We will add more to match the real world.”
As a result, it looks like SOLIDWORKS will be putting a lot of future work into this new feature. It will not be surprising to see Dassault Systèmes announce more abilities from the topology optimization tool in future releases.
About the Author
Shawn Wasserman (@ShawnWasserman) is the Internet of Things (IoT) and Simulation Editor at ENGINEERING.com. He is passionate about ensuring engineers make the right decisions when using computer-aided engineering (CAE) software and IoT development tools. Shawn has a Masters in Bio-Engineering from the University of Guelph and a BASc in Chemical Engineering from the University of Waterloo.