How to use the overhang constraint in Topology Optimization


Topology optimization in nTop offers some manufacturing constraints. One of those is the overhang constraint for additive manufacturing. This article teaches you how to use the constraint and shows you the differences between a constrained and unconstrained example.


Applies to:

  • nTop 2.24.5 +
  • Topology Optimization
  • Additive Manufacturing


  1. Add an Overhang Constraint block
  2. Define the Build direction as a vector. This corresponds to the direction of manufacture. If your part is already oriented on the X-Y plane, then this will typically be the Z+ direction, which corresponds to a vector of <0,0,1>.  Tip: This is an ideal parameter to use in DoEs to explore the solution space fully.
  3. Specify the max angle, which is the maximum allowable overhang angle allowed by the manufacturing process. 
  4. Specify the support boundaries, which are the regions you want to allow support structures to be applied to.  Use the FE Boundary by Body or FE Boundary by Flood Fill or FE Face Boundary. The support boundaries must use face selection, so be sure to select that in the boundary block.
  5. The Overhang Constraint can now be input into the Constraints list of an existing Topology Optimization.


Unconstrained results on the left, and results with an overhang constraint of 45 degrees on the right.


And that’s it! You’ve successfully used the overhang constraint for Topology Optimization

Are you still having issues? Contact the support team, and we’ll be happy to help!

Download the Example file:

More on this Topic:


 additive Top Opt topology optimization additive manufacturing constraint beta overhang 2.24 
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