Additive Manufacturing

Polymer AM Processes

Design for Additive Manufacturing

Self-Supporting Angles

Minimum self-supporting angle:
- Metal (DMLS): 45 degrees from horizontal
- Polymer (SLS): 0 degrees (self-supporting)
- FDM: 45 degrees (with support)
- SLA: 30-45 degrees

Overhang rule:
- Unsupported distance < 2 mm (metal)
- Unsupported distance < 5 mm (polymer)

Minimum Feature Sizes

Design Optimization

1. Topology Optimization

   • Define design space
   • Apply loads and constraints
   • Set mass reduction target
   • Interpret and refine results

2. Lattice Structures

   Type	Relative Density	Application
   Octet truss	10-40%	High stiffness
   Diamond	15-35%	Isotropic
   Gyroid	10-50%	Bone ingrowth
   Honeycomb	20-50%	Directional load

3. Part Consolidation

   • Identify assembly candidates
   • Evaluate function integration
   • Consider serviceability
   • Calculate cost/benefit

Build Preparation

Orientation Selection

Optimization criteria:
1. Minimize support volume
2. Optimize surface finish on critical surfaces
3. Reduce build height (time)
4. Ensure feature accuracy

Trade-off example:
- Flat orientation: Less support, rougher top surface
- Angled orientation: More support, better detail

Support Design

1. Support Types

   Type	Application	Removal
   Block	Large overhangs	Manual/machining
   Tree	Complex geometry	Manual
   Lattice	Heat dissipation	Manual
   Cone	Point supports	Manual

2. Support Minimization

   • Reorient part
   • Add self-supporting chamfers
   • Split and assemble
   • Modify geometry if allowed

Nesting and Packing

Minimum spacing:
- DMLS: 2-5 mm between parts
- SLS: 2-3 mm (powder acts as support)
- FDM: N/A (single part builds)
- SLA: 2-3 mm

Packing efficiency target: 5-15% of build volume

Post-Processing

Metal AM

1. Required

   • Stress relief (before removal)
   • Support removal
   • Heat treatment (as specified)

2. Optional

   • Machining critical surfaces
   • Shot peening
   • Polishing/finishing
   • HIP (for porosity closure)

Polymer AM

1. SLS/MJF

   • Depowder and clean
   • Dye or paint (optional)
   • Sealing (if required)

2. SLA/DLP

   • Wash (IPA or solvent)
   • UV post-cure
   • Support removal
   • Sanding/finishing

Process Integration

• ME-019: Additive Manufacturing Process Development

Input Schema

{
  "part_model": "CAD file reference",
  "material_requirement": {
    "type": "metal|polymer",
    "specific": "string (e.g., Ti6Al4V, Nylon 12)",
    "properties": "strength|stiffness|temperature|biocompatible"
  },
  "quantity": "number",
  "quality_requirements": {
    "tolerance": "number (mm)",
    "surface_finish": "string",
    "critical_features": "array"
  },
  "timeline": "prototype|production",
  "budget_constraint": "number (optional)"
}

Output Schema

{
  "process_recommendation": {
    "technology": "string",
    "material": "string",
    "machine": "string (if specific)"
  },
  "build_preparation": {
    "orientation": "description and rationale",
    "support_volume": "number (cm3)",
    "build_time": "number (hours)",
    "material_usage": "number (kg)"
  },
  "dfam_recommendations": [
    {
      "feature": "string",
      "issue": "string",
      "recommendation": "string"
    }
  ],
  "post_processing": "array of steps",
  "cost_estimate": {
    "material": "number",
    "machine_time": "number",
    "post_processing": "number",
    "total": "number"
  }
}

Best Practices

1. Design for AM from the start, not as afterthought
2. Understand process limitations before design
3. Optimize orientation for quality, not just time
4. Plan for post-processing in design stage
5. Validate material properties for application
6. Consider total cost including post-processing

Integration Points

• Connects with CAD Modeling for geometry
• Feeds into Material Testing for property validation
• Supports DFM Review for manufacturability
• Integrates with FAI Inspection for quality