By Paolo Olmos
I recently worked on a customer project which involved answering the question, "How can I represent complex sub-assemblies or components that are part of a larger assembly using SOLIDWORKS Simulation?" The customer wanted to include ball screws and linear rails. These sub-assemblies include bearings, threads, and complex mounting geometry that would require a significant amount of time and effort to setup - and a significant amount of time to solve. Additionally, if I were to miss an element in the setup, the analysis could fail or the results may be invalid. One way to simplify an analysis that involves complex sub-assemblies or components is to replace them with spring connectors. Replacing components with spring connectors allows you to:
- Reduce the number of components that need to be meshed, improving solve time
- Simplify the analysis setup, reducing the overall time necessary to execute the analysis
While maintaining the inherent stiffness of the components you remove by replacing them with an equivalent spring stiffness. As an example, let’s take an assembly made of 2 plates with a spring in the middle. Including the spring in a linear static analysis with a 100 lbf load applied, the results show a displacement of 0.282 inches. To use a spring connector in this situation, the spring component is suppressed and replaced with a virtual spring that uses the stiffness data you have for the modeled spring. As you can see in the screenshots below, we can get the same displacements as the analysis that included the modeled spring.
Right: Results With Spring, Left: Results With Spring Connector.
Comparing the setup and solve time between the two studies:
- The setup time was short for both studies, but imagine if the spring was a more complex sub-assembly or component. It would require time to define contacts, material, and fixtures for all the elements in the sub-assembly or component. The setup time could be substantially longer.
- The solve time for the actual spring took 6 seconds to solve versus 2 seconds for the spring connector analysis.
A couple of other things to consider when using spring connectors:
- Make sure that the face selected for one body shares a common projected area on the face selected for the other body. If you don’t, SOLIDWORKS Simulation cannot create the spring and will display an error when you try to run the analysis. In the example above, the faces selected had the same area and were directly overlapping when looking at the top view.
- You can create split lines to separate the faces of each body in order to create a common projected area between them. In the example above, this technique would have been required if the spring was significantly smaller than the plates.
As you can see in this brief overview, spring connectors can help you obtain accurate results, while saving you time to setup and solve your analysis. Keep a look-out at this space for a follow-up blog article that covers using spring connectors to represent the ball screw and linear rail assemblies mentioned earlier, or watch my webinar: SOLIDWORKS Simulation - Representing Ball Screws and Linear Rails in Your Analysis.