Compliant Mechanism 3D
The Compliant Mechanism 3D analysis extends the 2D compliant mechanism solver to three dimensions. It optimizes a volumetric material layout within a box-shaped design domain using the same design optimization approach, but with 3D mesh cells instead of 2D grid cells.
When to use this analysis
Use Compliant Mechanism 3D when:
- The mechanism requires out-of-plane motion (twist, lift, multi-axis output).
- The geometry cannot be approximated as a constant-thickness planar part.
- You need to import and optimize around a 3D STEP or STL part.
- You are designing 3D metamaterial unit cells.
Be aware of the significantly higher compute cost compared to 2D:
| Metric | 2D (100x50 grid) | 3D (50x25x25 grid) |
|---|---|---|
| Elements | 5,000 | 31,250 |
| DOFs | ~10,000 | ~100,000 |
| Typical iteration time | < 1 s | 10 -- 60 s |
| Memory | ~50 MB | ~500 MB -- 2 GB |
Reduce element count by increasing the element size or decreasing domain dimensions during early exploration, then refine for final runs.
Required boundary conditions
Same as 2D, but with three-dimensional parts and paths:
| Condition | Object type | Purpose |
|---|---|---|
| Input | Input Preserve + Linear/Rotational Path | 3D force application (any direction) |
| Output | Output Preserve + Linear/Rotational Path | 3D desired motion direction |
| Fixed | Fixed Preserve or Boundary Fixed Preserve | Prevents rigid-body motion |
3D scenes use Box Parts instead of Rectangle Parts for the design domain, and paths may point in any direction (not limited to XY plane).
Solver parameters
The 3D analysis accepts all parameters from the Compliant Mechanism 2D analysis, plus the following additions and differences.
Design domain (3D-specific)
| Parameter | Type | Default | Range | Description |
|---|---|---|---|---|
| Design domain depth | float | (from part) | > 0 | Depth (Z dimension) of the box-shaped design domain in mm. |
The number of elements in each direction is computed from the domain dimensions and element size. These are not directly editable parameters.
Fixed boundaries (3D)
| Parameter | Type | Default | Description |
|---|---|---|---|
| Fixed sides | list | None | Domain faces to fix. Options: Left, Right, Top, Bottom, Front, Back. |
Differences from 2D
| Aspect | 2D | 3D |
|---|---|---|
| Cell type | 2D grid cell | 3D grid cell |
| DOFs per node | 2 (x, y) | 3 (x, y, z) |
| Coordinate system | XY plane | XYZ, Z-up |
| Part types | Rectangle | Box, STEP, STL |
| Symmetry | Vertical mirror, Horizontal mirror | Not yet supported |
| Stress constraint | Supported | Not yet supported |
| Nonlinear analysis | Supported | Not yet supported |
Performance guidelines
- Start with an element size of 2--4 mm for exploration, then reduce to 1 mm or below for production runs.
- Keep total element count below 200,000 for interactive use. Above that, expect multi-minute iterations.
- The 3D solver parallelizes computation but is still memory-bound on large grids. Monitor system memory if you exceed 500,000 elements.
Solver output
Output format is identical to 2D, except:
- The material layout is three-dimensional.
- Displacement fields have 3 DOFs per node instead of 2.
- The exported STL mesh is a true 3D surface (extracted from the design result).