3D Printing

  • 3D printing is additive manufacturing where material is added layer by layer. 

What are the benefits of 3D printing? 

  1. Rapid prototyping at low cost
  2. Complex, custom designs
  3. Reduced material waste 

What are the limitations of 3D printing?  

  1. Not ideal for mass production 
  2. Limited material options 
  3. Post-Processing required for a nice surface finish

3D printing Technologies

FDM (Fused Deposition Modeling) – Uses melted plastic filament; affordable and common

Advantages: 

  • Speed (fast)
  • Larger build volume 
  • Larger material options and colors 
  • Material is cheaper and yields higher quantity

Disadvantages 

  • Low resolution. Thick layer height is not ideal for parts with small details, and surface finish will be rough. Post-processing is required which increases production time. 
  • Parts are weakest in the z direction. Layer adhesion limits mechanical performance. 

Design Rules: 

  • Minimum wall thickness should be twice nozzle diameter. 
  • Parts on angle overhangs greater than 45 degrees should have supports 
  • Orient for strength. Avoid placing tensile stresses perpendicular to layer lines 
  • Place critical dimesnions in the X-Y plane 

 

SLA (Stereolithography) – Uses UV light to cure liquid resin; high detail

Advantages: 

  • High resolution and surface finish. Layer lines can be 25um
  • Used for complex geometry. Intricate features, and thin walls achievable beyond FDM limits 

Disadvantages: 

  • Material Brittleness: Many resins are brittle under impact; tough resins trade resolution for durability
  • Environmental & Safety: Liquid resins are toxic until cured; require gloves, ventilation, and waste disposal protocols.
  • Post-Process Overhead: Washing, UV curing, and support removal add time and labor.
  • Cost of Resin & Maintenance: Photopolymer resins are more expensive per part than FDM filaments.
  • Support locations cause surface to be rough and are difficult to sand

Design Rules:

  • Unsupported walls: ≥ 0.6 mm for standard resins; some high-detail resins allow 0.3–0.5 mm walls but risk tear-away during peel
  • Supported walls: ≥ 1.0 mm to ensure consistent cure and avoid “slumping” under peel forces
  • Up to ~45° can often print cleanly; beyond this, sagging or delamination occurs
  • Volumetric shrinkage: Photopolymerization induces 1–5% shrinkage. Compensate with CAD scaling (usually +0.1–0.3%) and uniform wall thickness to minimize distortion

SLS (Selective Laser Sintering) – Uses a laser to fuse powder; strong and functional

SLS uses a finely spread powder that both forms the part and acts as its own support.

 

  • Design freedom: No need for supports; intricate geometries and internal features.
  • Mechanical isotropy: Nearly equal strength in all directions.
  • Rapid batch production: Nesting dozens of parts in a single build.

Disadvantages

  • Surface finish: Grainy, matte texture; post‐processing required for smoothness
  • Powder handling: Hygroscopic powders require controlled storage; sieving and recycling add labor.
  • Equipment cost: Industrial‐grade machines and sintering ovens are expensive.