What post-processing steps are required for metal vs plastic prints?
Fundamental Differences in Post-Processing Approaches
Post-processing for metal and plastic 3D printed parts diverges significantly due to their inherent material properties and the printing technologies used. Metal parts, often produced via SLM or DMLS, require intensive thermal and mechanical treatments to become functional, while plastic parts typically need more cosmetic and support-removal focused finishing.
Critical Post-Processing for Metal Prints
Metal 3D prints are in a high-stress, "green" state immediately after printing and require a multi-step workflow to achieve their mechanical properties and dimensional accuracy.
Stress Relief & Thermal Treatment: Immediately after printing, parts undergo stress relief heat treatment to prevent distortion and reduce internal stresses locked in during the rapid melting and solidification process.
Support Removal: Metal supports are often structurally fused to the part and require removal via CNC Machining or wire EDM, which is far more complex than plastic support removal.
Hot Isostatic Pressing (HIP): For critical aerospace or medical applications, HIP is used to eliminate internal micro-porosity, significantly improving fatigue life and part density.
Final Machining: Critical functional surfaces and interfaces almost always require precision Post Machining to achieve tight tolerances and a smooth surface finish that the as-printed state cannot provide.
Surface Finishing: Techniques like Sand Blasting (bead blasting) are used for a uniform matte finish. Further enhancements like Anodizing (for aluminum) or polishing can be applied for corrosion resistance and aesthetics.
Common Post-Processing for Plastic Prints
Post-processing for plastic parts, such as those from FDM or SLS, is generally less intensive and focuses more on aesthetics and basic cleanup.
Support Removal: For FDM parts, this is a manual process. For technologies like SLA, it often involves washing in a solvent and then carefully breaking or cutting supports away.
Surface Smoothing: Many plastic parts exhibit layer lines. Techniques range from manual sanding and Tumbling for simple parts to chemical vapor smoothing (e.g., using acetone for ABS) for a glossy, injection-molded-like finish.
Curing: Resin-based prints (SLA/DLP) require post-printing UV curing to fully polymerize the resin and achieve their final mechanical strength.
Cosmetic Finishing: Plastic parts are often primed and Painting for color or Powder Coating for a more durable and textured finish.
Comparison and Workflow Integration
The core distinction is that metal post-processing is often mandatory for structural integrity, involving high-energy thermal and machining processes. In contrast, plastic post-processing is frequently optional and cosmetic, though it is crucial for creating market-ready products. Within a full One-Stop Service, these steps are integrated seamlessly. A part may be Rapid Prototyping via 3D printing in plastic for form and fit, and then move to Aluminum Die Casting for mass production, with its own distinct Post Process route.
