What Post-Processing Techniques are Most Common for Plastic 3D-Printed Parts?

Support Removal and Initial Cleaning

The most universal post-processing step for plastic 3D-printed parts is the removal of support structures and residual material. For Fused Deposition Modeling (FDM) parts, this involves manual breaking, cutting, or sanding. For Stereolithography (SLA), Digital Light Processing (DLP), and other resin-based parts, the process is more involved. Parts are typically rinsed in a solvent bath (e.g., isopropyl alcohol) within an ultrasonic or agitation washer to dissolve uncured resin, followed by a secondary clean rinse. This is a prerequisite for all plastic 3D printing workflows to ensure a clean surface for subsequent finishing and curing.

Surface Finishing and Smoothing

To improve aesthetics and function by eliminating layer lines, several surface finishing techniques are standard. Sanding and Polishing: A manual, multi-stage process using progressively finer grits of sandpaper, often followed by buffing with polishing compounds for a glossy finish. Chemical Smoothing: For specific thermoplastics like ABS, exposure to solvent vapors (e.g., acetone) gently melts the outer surface, fusing layer lines into a smooth, glossy finish. Media Tumbling/Bead Blasting: Parts are placed in a tumbler with abrasive media or blasted with fine glass beads to uniformly create a consistent, satin matte finish, ideal for visual prototypes.

Accuracy, Machining, and Coating

For engineering parts requiring tight tolerances or specific functional surfaces, subtractive methods are integrated. CNC machining is used to achieve precise holes, flat sealing surfaces, or accurate threads. Priming, Painting, and Coating: Applying primer filler helps to mask minor layer lines, followed by spray painting for color or texture. Functional coatings can be added for UV protection, moisture resistance, or specific dielectric properties, especially for high-performance materials like PEEK used in demanding aerospace and aviation applications.

Assembly and Performance Enhancement

Final assembly and property enhancement are key for end-use parts. Adhesive Bonding and Welding: Plastic parts are commonly joined using industrial adhesives, ultrasonic welding, or solvent welding to create strong assemblies. Annealing: A critical post process step where the part is heated in a controlled oven below its melting point. This relieves internal stresses from printing, improves dimensional stability, and can significantly increase heat resistance and mechanical strength, which is validated through material testing and analysis.