What Are the Most Common Post-Processing Techniques for Plastic Parts?

Essential Support Removal and Cleaning

The most immediate and common post-processing step for plastic parts, especially from plastic 3D printing, is support removal and cleaning. For fused deposition modeling (FDM) parts, this involves manually or with tools breaking away support structures, followed by sanding to smooth contact points. For stereolithography (SLA) and similar resin-based processes, parts undergo washing in solvents like isopropyl alcohol to remove uncured liquid resin, and are then post-cured under UV light to achieve final polymerization and mechanical stability. Proper cleaning is foundational for all subsequent finishing and material testing and analysis.

Surface Finishing for Aesthetics and Function

To eliminate layer lines and achieve desired surface qualities, several techniques are standard. Sanding and Polishing: A manual multi-stage process using progressively finer grits, often followed by polishing compounds, to create a smooth, glossy finish. Vapor Smoothing: Particularly for parts made from ABS, this involves exposing the part to solvent vapors which slightly melt the surface, fusing layer lines into a smooth finish. Media Blasting (Bead Blasting): Using fine glass beads or other soft media under pressure to uniformly texture the surface, resulting in a consistent, satin-like matte finish that is ideal for visual prototypes and functional parts.

Dimensional Accuracy and Machining

For engineering applications requiring tight tolerances on specific features, subtractive machining is often employed. CNC machining is used to drill precise holes, create flat sealing surfaces, or achieve accurate threads that may be challenging to print directly. This hybrid manufacturing approach combines the design freedom of additive manufacturing with the precision of CNC. Similarly, deep hole drilling techniques can be adapted for plastics where required.

Joining, Assembly, and Coating

Many plastic parts require assembly or enhanced surface properties. Adhesive Bonding & Welding: Plastic parts are commonly assembled using specialized industrial adhesives or welding techniques like ultrasonic, friction, or solvent welding for strong, permanent bonds. Painting and Coating: Priming and painting are used to apply color, provide UV protection, or add a specific texture. Functional coatings can also be applied for purposes like moisture resistance or electrical insulation. For high-performance thermoplastics like PEEK, these treatments ensure performance in demanding sectors like aerospace and aviation or medical and healthcare.

Performance Enhancement Treatments

For functional prototypes and end-use parts, treatments to enhance mechanical or thermal properties are critical. Annealing: Controlled heat treatment below the material's distortion temperature relieves internal stresses from the printing process, improving dimensional stability and increasing heat resistance and strength. Infiltration: For porous plastic parts, a penetrating sealant (e.g., epoxy, wax) is used to fill voids, creating a watertight and stronger component. These post process steps are vital for ensuring the reliability of plastic parts in critical applications.