Lesson 9.3: Post-Processing for Plastic and Resin 3D Printing

🧩 Why Post-Processing Is Essential for Polymers

Unlike metals, plastic/resin 3D prints often:

• Show visible layer lines and surface artifacts

• Contain uncured resin or support residues

• Lack final mechanical or aesthetic polish

• Require dimensional tuning or assembly preparation

Post-processing ensures:
✔️ Functional fit
✔️ Better strength and appearance
✔️ Regulatory or customer requirements
✔️ Enhanced chemical/UV resistance

🧼 1. Cleaning and Curing (Primarily SLA/DLP/LCD Resin Prints)

🔹 Cleaning:

• Purpose: Remove uncured resin from the surface.

• Method: Submersion or agitation in Isopropyl Alcohol (IPA) or tripropylene glycol monomethyl ether (TPM).

🔬 Automated wash stations (e.g., Form Wash) improve consistency and safety.

🔆 Curing:

• Purpose: Finalize polymerization to improve mechanical properties.

• Method: UV curing chambers (typically 405 nm) for 5–60 min depending on resin and geometry.

⏱️ Post-cure can increase hardness, biocompatibility, and thermal resistance by up to 50%.

❗ Safety note: Resin exposure can be hazardous—always wear gloves and ensure good ventilation.

🛠️ 2. Support Removal and Surface Smoothing

🧹 Support Removal:

• Manual Cutting (flush cutters or knives)

• Ultrasonic Cleaning for fine detail parts

• Media Blasting (e.g., glass beads or soda blasting) to clean surfaces gently

🪵 Surface Smoothing:

Surface roughness (Ra) can be reduced from ~20–50 µm to <5 µm with proper smoothing.

🎨 3. Painting and Coating

🎯 Purpose:

• Improve visual appearance, UV resistance, or chemical barrier.

🎨 Painting Workflow:

1. Sanding and Priming

2. Base Coat (Spray or Airbrush)

3. Detailing (optional)

4. Protective Top Coat (e.g., clear polyurethane)

💡 Automotive paints or acrylics are commonly used. Primers improve paint adhesion.

🧴 Coatings:

🔗 4. Assembly and Joining

🧩 Techniques:

🧠 Designers should consider assembly needs during CAD modeling (e.g., adding alignment pins or chamfers).