> For the complete documentation index, see [llms.txt](https://dante-solutions-inc.gitbook.io/dante-6.3-help-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://dante-solutions-inc.gitbook.io/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space.md).

# Applying Mechanical Boundary Conditions in Free Space

This section details how to properly fix a 3D model in free space. Simple shapes are shown; however, most complex shapes can be fixed according to simple shapes. In other words, a bevel gear can be fixed like a simple ring. This section shows: [**Fixing a 3D Cube**](/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space/fixing-a-3d-cube.md)**,** [**Fixing a 3D Cylinder**](/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space/fixing-a-3d-cylinder.md)**,** [**Fixing a 3D Ring**](/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space/fixing-a-3d-ring.md), and [**Fixing Sphere 3D**](/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space/fixing-sphere-3d.md). An example is also given on what happens when the component is not fixed properly in free space; i.e., the component is over constrained. Please reference [**Over Constrained Boundary Conditions**](/dante-6.3-help-documentation/readme/additional-topics-introduction/applying-mechanical-boundary-conditions-in-free-space/over-constrained-boundary-conditions.md).

In order to understand the terms described below, some background must be defined. The most important tool when starting to fix an object in free space is the triad, shown below. This allows for a visual representation for the process. Free space in three dimensions has 6 degrees of freedom, 3 translational and 3 rotational. 3 translational degrees of freedom allow for movement in the X, Y, and Z directions, while the 3 rotational represent rotations about the X, Y, and Z axes.

A properly fixed part will prevent free motion in these 6 degrees of freedom, while allowing the part to expand and contract naturally due to thermal and phase transformation induced strains. If over constrained, preventing natural motion, the stress and displacement results will be incorrect.