7.3 Materials and Finishing Techniques in 3D Printing

3D printing materials range from plastics to metals and composites, each with unique properties. Thermoplastics like PLA and ABS are popular for their ease of use, while metals and composites offer strength and specialized applications.

Finishing techniques elevate 3D printed objects, transforming rough prints into polished masterpieces. From support removal and sanding to painting and polishing, these methods enhance aesthetics and functionality, opening up endless creative possibilities in 3D printing.

Materials in 3D Printing

Materials for 3D printing

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• Plastics encompass a wide range of materials commonly used in 3D printing
  • Thermoplastics can be melted and reformed multiple times, making them suitable for 3D printing
    • PLA (Polylactic Acid) is derived from renewable resources (corn starch) and is biodegradable
    • ABS (Acrylonitrile Butadiene Styrene) offers strength, durability, and heat resistance but may warp during printing
    • PETG (Polyethylene Terephthalate Glycol) provides good layer adhesion and is less brittle than PLA, making it food-safe
    • Nylon has a high strength-to-weight ratio, flexibility, and chemical resistance
    • TPU (Thermoplastic Polyurethane) is elastic, abrasion-resistant, and suitable for wearables (watch straps) and gaskets
  • Thermosets undergo a chemical reaction during printing and cannot be melted and reformed once cured
    • Resin is used in SLA (Stereolithography) and DLP (Digital Light Processing) printing, offering high detail and smooth surface finish but requiring post-curing
• Metals can be 3D printed using techniques such as SLM (Selective Laser Melting) and DMLS (Direct Metal Laser Sintering)
  • Stainless steel is strong, corrosion-resistant, and suitable for functional parts (gears, valves)
  • Aluminum is lightweight and has good thermal conductivity, making it useful in aerospace and automotive industries
  • Titanium offers a high strength-to-weight ratio and biocompatibility, ideal for medical implants (hip replacements)
  • Gold and silver are used for jewelry and decorative objects
• Composites combine two or more materials to achieve desired properties
  • Carbon fiber and glass fiber reinforced polymers offer high strength and lightweight, useful in aerospace and automotive applications
  • Ceramic-based composites are heat-resistant, wear-resistant, and used in high-temperature applications (rocket nozzles)
  • Metal-polymer composites combine the strength of metals with the flexibility of polymers

Properties of printing materials

• Thermoplastics have varying properties that make them suitable for different applications
  • PLA is biodegradable, has a low melting point, and is good for beginners due to its ease of use
  • ABS is strong, durable, and heat-resistant but prone to warping during printing
  • PETG offers good layer adhesion, is less brittle than PLA, and is food-safe, making it suitable for kitchen utensils
  • Nylon has a high strength-to-weight ratio, flexibility, and chemical resistance, ideal for functional parts (gears, bearings)
  • TPU is elastic, abrasion-resistant, and suitable for wearables (shoe soles) and gaskets
• Thermosets like resin offer high detail, smooth surface finish, but are brittle and require post-curing
• Metals have different properties depending on the specific alloy
  • Stainless steel is strong, corrosion-resistant, and suitable for functional parts (engine components)
  • Aluminum is lightweight, has good thermal conductivity, and is used in aerospace and automotive industries
  • Titanium has a high strength-to-weight ratio, is biocompatible, and is used in medical implants (dental implants)
  • Gold and silver are used for jewelry and decorative objects due to their aesthetic appeal
• Composites combine the properties of their constituent materials
  • Carbon fiber and glass fiber reinforced polymers are high strength, lightweight, and used in aerospace and automotive applications (aircraft components)
  • Ceramic-based composites are heat-resistant, wear-resistant, and used in high-temperature applications (brake pads)
  • Metal-polymer composites combine the strength of metals with the flexibility of polymers, offering unique properties

Finishing Techniques in 3D Printing

Post-processing of printed objects

• Support removal is necessary for objects printed with support structures
  1. Manual removal using pliers, cutters, or scrapers
  2. Dissolving soluble support materials (PVA) in water
• Sanding improves surface quality and smoothness
  1. Progressive sanding with increasing grit sandpaper (120, 240, 400, 600)
  2. Wet sanding for a smoother finish, using water to lubricate the sandpaper
• Filling and smoothing address gaps and imperfections in the printed object
  • Epoxy or putty can be used to fill gaps and imperfections, creating a seamless surface
  • Acetone vapor smoothing is effective for ABS prints, melting the surface layer to create a glossy finish
• Priming and painting enhance the appearance and durability of the object
  1. Applying primer improves paint adhesion and helps hide layer lines
  2. Painting with acrylic, enamel, or spray paints allows for customization and protection
• Polishing creates a glossy or matte finish
  • Buffing with polishing compound results in a glossy finish, using a cloth or buffing wheel
  • Tumble polishing with abrasive media (ceramic pellets, steel shot) is effective for small parts, creating a uniform finish

Enhancements in 3D printing

• Color can be added to 3D printed objects in various ways
  • Full-color 3D printing using inkjet technology (Stratasys J750) allows for vibrant, multi-colored prints
  • Mixing colored filaments or resins creates unique color combinations
  • Hand-painting or dyeing post-print allows for customization and artistic expression
• Texture can be incorporated during the printing process or added post-print
  • Applying texture during printing using specialized software (Cura, Simplify3D) creates intricate surface patterns
  • Creating texture with post-processing techniques (sanding, etching, embossing) adds depth and visual interest
  • Using textured filaments (wood-fill, metal-fill, stone-fill) mimics the appearance of natural materials
• Multi-material printing combines different materials in a single print
  • Combining flexible and rigid parts creates objects with varying properties (phone cases with flexible buttons)
  • Using soluble support materials enables printing of complex geometries and interlocking parts
  • Embedding electronic components or sensors during the printing process creates functional, interactive objects (LED-illuminated sculptures)