> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
> Use this file to discover all available pages before exploring further.

# How to use the Overhang Constraint

## Objective:

nTop offers some manufacturing constraints, including the **Overhang Constraint** for additive manufacturing. This article teaches you how to use the constraint and shows the differences between a constrained and unconstrained example.

![A gif showing a body before applying an Overhang Constraint and after.](https://files.learn.ntop.com/help-articles/optimization/1500001061222.png)

## Applies to:

* Optimization
* Additive Manufacturing

## Procedure:

1. Add an **Overhang Constraint** block

![The Overhang Constraint block](https://files.learn.ntop.com/help-articles/optimization/43450899722515.png)

2. Define the **Build direction**as a vector. This corresponds to the direction of manufacturing. If your part is already oriented on the X-Y plane, then this will typically be the Z+ direction, corresponding to a vector of \<0,0,1>.

\*\*\*Tip:\**This is an ideal parameter for DoEs to explore the solution space fully.*

3. Specify the ***Max Angle***, the maximum allowable overhang angle that the manufacturing process allows.

4. Specify the ***Support Boundaries*** (optional), which are the regions you want to allow support structures to be applied to. Use the [**FE Boundary by Body**](/help-articles/knowledge-base/structures/how-to-select-boundaries-using-boundary-by-body), [**FE Boundary by Flood Fill**](/help-articles/knowledge-base/structures/how-to-select-boundaries-of-an-fe-mesh-fe-boundary-by-flood-fill), or **FE Face Boundary**. The support boundaries need to use Face selection, so please select that in the boundary block.

5. Check the ***Auto-Detect Support*** if you would like to auto-detect the faces of the design space that can provide support for the given print direction and overhang angle.

6. Check the ***Include Passive*** if you would like to include the passive region in the overhang region optimization. If not selected, the passive regions will be ignored.

7. The **Overhang Constraint** can now be input into the Constraints list of an existing Topology Optimization.

![The Body on the left was generated without an Overhang Constraint and the body on the right was generated with an Overhang Constraint of 45 degrees.](https://files.learn.ntop.com/help-articles/optimization/50006642584595.png)*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](https://support.ntopology.com/hc/en-us/requests/new), and we'll be happy to help!

## Download the Example file:

* [Example file](https://files.learn.ntop.com/Support%20Article%20Example%20Files/Knowledge%20Base/Optimization/overhang_constraint.ntop)

## Keywords:

*additive Top Opt topology optimization additive manufacturing constraint beta overhang 2.24*