Process Principles
LOM (Laminated Object Manufacturing)
LOM is an additive manufacturing process that uses layers of adhesive-coated sheet materials (such as paper, plastic, metal foil, or ceramic tape) to construct 3D objects. A laser or blade cuts each layer according to the digital cross-section before a new layer is bonded on top. The process involves:
Layer deposition: Unwinding material from a supply roll and bonding it to the stack using a heated roller that activates the adhesive.
Cross-section cutting: Using a laser or blade to cut the layer outline and cross-hatch excess material for removal.
Stack lowering and repetition until the part is complete.
Post-processing: Removing excess material to reveal the final object.
FDM (Fused Deposition Modeling)
FDM is an extrusion-based additive process where thermoplastic filaments are heated to a semi-liquid state and deposited layer by layer. The process involves:
Material feeding: Filament spool fed through a heated nozzle.
Nozzle movement: The nozzle moves horizontally, depositing material along the designated path.
Layer cooling: Deposited material cools and solidifies rapidly.
Support structures: Required for overhangs, often using water-soluble materials for easy removal.
Technical Specifications
| Characteristic | LOM | FDM |
| Layer Thickness | Varies with sheet material thickness | Typically 0.1–0.3 mm |
| Materials | Paper, plastics, ceramics, metal foils | Thermoplastics (ABS, PLA, PC, PPSF) |
| Print Speed | Fast for large, simple parts | Slower due to extrusion process |
| Accuracy | Moderate to high (±0.1 mm) | Moderate (±0.127–0.3 mm) |
| Surface Finish | Stair-stepping effect, requires sanding | Layer lines visible, may require finishing |
| Support Structures | Not required | Required for overhangs and complex geometries |
| Build Volume | Large volumes possible | Limited by nozzle movement range |
| Strength | Anisotropic (weaker in Z-axis) | Anisotropic (weaker in Z-axis) |
Material Considerations
LOM Materials
Paper: Most common, low cost, but hygroscopic (requires sealing).
Plastic Films: Better durability than paper.
Metal Foils: For specialized applications, requiring specialized equipment.
Ceramic Composites: Under development for technical applications.
FDM Materials
ABS (Acrylonitrile Butadiene Styrene): Good strength, slightly toxic emissions.
PLA (Polylactic Acid): Biodegradable, easier to print, lower strength.
PC (Polycarbonate): Higher strength and temperature resistance.
PPSF (Polyphenylsulfone): Highest strength and thermal resistance.
Composite Filaments: With wood, metal, or carbon fiber additives.
Design Guidelines
Designing for LOM
Optimize for the process: LOM is suitable for large parts with relatively simple geometries.
Avoid intricate features: Fine details and internal cavities are difficult.
Consider post-processing: Account for material removal and sealing requirements.
Flat surfaces preferred: Minimizes stair-stepping effect.
Designing for FDM
Overhangs and supports: Design to minimize support material usage.
Wall thickness: Ensure minimum wall thickness for structural integrity.
Tolerances: Account for layer adhesion and potential warping.
Orientation: Part orientation affects strength and surface quality.
Applications and Use Cases
Typical LOM Applications
Concept models and prototypes for visual assessment.
Sand casting patterns and mold making (wood-like properties).
Large-scale models for architectural and aerospace industries.
Educational models due to low material cost.
Typical FDM Applications
Functional prototyping for form and fit testing.
End-use parts for low-stress applications.
Manufacturing tools, jigs, and fixtures.
Customized medical devices and prosthetics.
Educational models and DIY projects.
Advantages and Limitations
LOM Advantages
High build speed for large, simple parts.
Low material cost (especially paper-based systems).
No support structures required.
Large build volumes possible.
Good mechanical properties in XY plane.
LOM Limitations
Limited accuracy for fine features.
Poor surface finish requires post-processing.
Material limitations (primarily paper).
Waste generation from support material.
Hygroscopic nature requires sealing.
FDM Advantages
Wide material selection with various properties.
Office-friendly operation with minimal emissions.
Multi-color printing capabilities.
Water-soluble supports for complex geometries.
Lowest cost equipment and materials among 3D printing technologies.
FDM Limitations
Anisotropic strength (weaker in Z-direction).
Layer adhesion issues can affect part strength.
Visible layer lines require post-processing for smooth surfaces.
Slow build speeds for high-resolution parts.
Warpping and shrinkage issues with some materials.
Post-Processing Requirements
LOM Post-Processing
Decubing: Removing support material (can be time-consuming).
Sealing: Required to prevent moisture absorption (varnish, epoxy).
Sanding: To reduce stair-stepping effect.
Painting: For improved appearance.
FDM Post-Processing
Support removal: Breaking away or dissolving support material.
Sanding: Smoothing layer lines.
Chemical smoothing: Using solvents (e.g., acetone for ABS).
Priming and painting: For cosmetic parts.
Annealing: Heat treatment to improve strength.
Cost Considerations
LOM Costs
Equipment: Moderate to high ($30,000+).
Materials: Low cost (especially paper).
Operation: Requires dedicated environment, maintenance cost high.
Labor: Significant post-processing time required.
FDM Costs
Equipment: Low to moderate (desktop units from few hundred dollars).
Materials: Moderate cost ($20-50/kg for standard materials).
Operation: Office environment possible, low maintenance.
Labor: Minimal post-processing for basic parts.
Environmental Impact
LOM Environmental Considerations
Paper-based systems are renewable and biodegradable.
Waste material may be recycled or composted (paper systems).
Energy consumption during processing.
FDM Environmental Considerations
Petroleum-based plastics (ABS) are not biodegradable.
PLA is biodegradable under industrial conditions.
Energy consumption during extrusion.
Limited recycling options for failed prints.
Future Developments
LOM Innovations
New materials including metals, ceramics, and composites.
Improved accuracy through better cutting technologies.
Faster processing with advanced bonding techniques.
Color printing capabilities through inkjet printing.
FDM Innovations
Higher temperature materials for improved performance.
Faster print speeds through advanced extruder designs.
Multi-material printing with interchangeable nozzles.
Higher resolution with smaller nozzle diameters.
Conclusion: Selecting the Right Technology
Choose LOM when:
You need large, simple parts quickly.
Cost is a primary concern (low material costs).
Surface finish is not critical.
Wood-like properties are acceptable or desirable.
Choose FDM when:
You require functional prototypes or end-use parts.
Design complexity is high with overhangs and internal features.
Multiple materials or colors are needed.
Office environment operation is preferred.
Both LOM and FDM have distinct advantages and limitations that make them suitable for different applications. Understanding these differences is essential for selecting the appropriate technology for your specific manufacturing needs. As both technologies continue to evolve, we can expect to see improvements in materials, accuracy, and capabilities that will further expand their applications in manufacturing and prototyping.
