Deep learning has revolutionized AM by enabling: (1) real-time process monitoring through image analysis, (2) surrogate models that replace expensive simulations, (3) generative design of novel structures, and (4) physics-constrained predictions that respect conservation laws.
Deep Learning Architectures for AM
CNN, GAN, VAE, Transformer, and Physics-Informed Neural Networks for additive manufacturing applications
Deep learning architectures provide the computational backbone for ML applications in additive manufacturing. From CNNs for image-based quality control to GANs for design generation and PINNs for physics-constrained simulation, understanding these architectures is essential for implementing ML in AM workflows.
Overview
Convolutional Neural Networks
AM Applications
| Application | Architecture | Input | Output |
|---|---|---|---|
| Defect classification | ResNet, VGG | Layer images | Defect type |
| Melt pool analysis | Custom CNN | Thermal images | Geometry features |
| Microstructure prediction | U-Net | Process parameters | Grain structure |
| Surface roughness | CNN regression | Surface images | Ra value |
| Topology optimization | Encoder-decoder | Boundary conditions | Material distribution |
Key Architectures
ResNet (Residual Networks)
Skip connections enable training very deep networks. Used for classification tasks with high accuracy.
- Depth: 18, 50, 101, 152 layers
- AM use: Defect classification, quality prediction
U-Net
Encoder-decoder with skip connections. Standard for segmentation and image-to-image translation.
- Strength: Works with small datasets
- AM use: Melt pool segmentation, porosity detection
EfficientNet
Compound scaling of depth, width, resolution. Best accuracy/efficiency tradeoff.
- Versions: B0-B7 (increasing complexity)
- AM use: Real-time monitoring with limited compute
Generative Models (GAN, VAE)
Generative Adversarial Networks
GANs learn to generate realistic samples by adversarial training between generator and discriminator.
| GAN Type | AM Application | Key Feature |
|---|---|---|
| cGAN (Conditional) | Design generation | Controls output properties |
| Pix2Pix | Image-to-image translation | Thermal to defect maps |
| CycleGAN | Domain adaptation | Sim-to-real transfer |
| StyleGAN | Microstructure synthesis | High-resolution, controllable |
| 3D-GAN | Lattice structure design | Volumetric generation |
Variational Autoencoders
VAEs learn compressed latent representations useful for design exploration:
- Latent space interpolation: Smooth transitions between designs
- Inverse design: Map from properties to designs
- Uncertainty quantification: Probabilistic outputs
- Anomaly detection: High reconstruction error = defect
Diffusion Models
Emerging architecture for high-quality generation:
- Denoising process: Iteratively refines random noise into samples
- AM potential: Design generation, data augmentation
- Current limitation: Slow sampling speed
Physics-Informed Neural Networks
PINNs embed physical laws directly into neural network training, ensuring predictions respect conservation of mass, momentum, and energy.
Formulation
Loss function combines data fit and physics residuals:
- L_data: MSE between predictions and measurements
- L_physics: Residual of governing PDEs (heat equation, Navier-Stokes)
- L_boundary: Boundary condition satisfaction
- Total: L = w1*L_data + w2*L_physics + w3*L_boundary
AM Applications
| Physics | Governing Equation | AM Application |
|---|---|---|
| Heat transfer | Heat equation | Melt pool temperature prediction |
| Fluid flow | Navier-Stokes | Melt pool convection |
| Solid mechanics | Elasticity equations | Residual stress prediction |
| Phase change | Stefan problem | Solidification modeling |
Advantages for AM
- Data efficiency: Physics reduces need for labeled data
- Extrapolation: Better generalization outside training domain
- Interpretability: Predictions respect known physics
- Multi-fidelity: Combines simulation and experimental data
Transformers & Attention
Self-Attention Mechanism
Captures long-range dependencies in sequential or spatial data:
- Vision Transformer (ViT): Image patches as tokens
- BERT-style: Pre-training on unlabeled AM data
- Temporal: Process monitoring time series
AM Applications
| Architecture | Application | Advantage |
|---|---|---|
| Vision Transformer | Layer-wise defect detection | Global context |
| Temporal Transformer | Sensor data analysis | Long-range dependencies |
| Graph Transformer | Lattice structure analysis | Topology awareness |
| Point Cloud Transformer | 3D scan processing | Unordered point sets |