Underconstrained Body Detection in 2016 SOLIDWORKS Simulation

2016 SOLIDWORKS Simulation has added enhancements to make the engineers life easier. One of the enhancements is the Underconstrained Bodies tool.  This tool allows the engineer to quickly and easily find the underconstrained bodies in their assembly, or multi body part.


We have all seen the error message “model is unstable” before causing us to scratch are heads and revisit the model and simulation setup.  Prior to 2016 the steps taken to underconstrained this error would have been as follows.

  • Switch to the model tab of SOLIDWORKS and “Interference Detection” on the Evaluate command manager tab.  Use the “treat coincidence as interference” option to see where the Automatic Bonded contact is applied.  Any area that is not shown in coincidence will not have the Global Bonded Contact applied.
  • Under the study properties, turn on “Use Soft Springs”.  Soft Springs applies tiny mass less springs to the geometry to artificially hold it in place.
  • Run the analysis again.  The Large displacement warning may appear, choose “No” to the large displacement option.
  • View the stress plot in an exaggerated scale, and animate the results.  The parts that move away from the rest of the model need additional constraints added.

Note: If the user has access to Simulation Professional the user could do a frequency study and achieve the same results as above.

The above process seems lengthy and in reality depending upon the model it is.  New for 2016 is the Underconstrianed Body Detection.  This option streamlines the process outlined above and give better insight into which body or bodies are underconstrained, and what degrees of freedom the body or bodies can move within.

To use the Underconstrained Body Detection in 2016 SOLIDWORKS Simulation is simple and intuitive.

  • Right mouse button on the Connections folder in the Simulation tree.
  • Choose “Find Underconstrained Bodies”
  • Select Calculate

Underconstrained Bodies Light

Under constrained


As shown above once calculated the bodies that are underconstrained will be shown when selected from the list in a shaded display.  The display will automatically start moving the body in the direction of the degree of freedom.

This enhancement continues to help the engineer be faster at finding the cause of the warning.  Additional new functionality that allows “Automatic Shell Bonding” can be used in conjunction with the Underconstrained Body Detection making the engineer better, faster, and smarter.

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