Though 3D printing is broadly perceived as a one-stop solution to manufacturing things from A to Z, most 3D printed parts must go through post-processing. In this article, we explain what exactly that is, why it's undertaken, and elaborate on how fundamental post-processing techniques contribute to the excellent final products driving investments in additive manufacturing today.
What Is Post-Processing?
Post-processing encompasses the work done on a 3D model after its initial creation by a printer. Similarly to how traditional manufacturing requires finishing touches, 3D printed objects often need additional refinement to meet quality standards and functional requirements. Post-printing operations can range from basic support removal to complex surface treatments. The average 3D-printed product must go through multiple phases to meet quality, appearance, and performance expectations.
What's the Point of Post-Processing?
The purpose of post-processing extends beyond mere aesthetics. In precision-critical applications like aerospace, as well as in industries where dimensional accuracy is paramount, post-processing ensures parts meet strict tolerances. Medical devices require specific surface finishes for biocompatibility and sterilization. Consumer products need attractive, durable finishes to compete in the marketplace. Even prototypes benefit from post-processing to better represent final production pieces.
Post-Processing Techniques Pivotal to Production Excellence
Post-processing can be as minimal or as extensive as the manufacturer wants it to be. Technology, material properties, and end-use requirements all factor into workflow plans. The following techniques are some of the most common and essential post-processing operations used by industrial producers today:
Support Removal
In 3D printing, supports are small structures designed to hold up overhanging parts that would otherwise collapse during the production process. Think of them as temporary scaffolds of sorts; slicing software automatically generates these small side connections with the intention they be removed post-printing.
Removal looks different depending on the printer and material at hand.
Fused Deposition Modeling (FDM®) and Fused Filament Fabrication (FFF) machines draw from a single spool, so any structural support is made from whatever polymer was used. That requires finishers to manually cut extrusions using pliers, flush cutters, or other specialty removal tools. While support structures can be designed to break off easily, removing them bit by bit always adds time to the process and creates opportunities for imperfections.
Then there are soluble supports. Unless such material is used for an entire design, soluble structural connections are only possible with dual-extruder 3D printers. The model itself is made from one material, and the supports are from a dissolvable compound like HIPS or PVA.
Solubility may or may not be worth the investment for manufacturers — it's ultimately a question of whether individual, manual support removal can be done cost-effectively at the given scale. While upfront costs are higher, automated dissolution can dramatically reduce labor hours and improve consistency across production runs.
Joining
Joining is especially relevant to producers with less robust additive manufacturing capabilities. It refers to the process of connecting multiple 3D printed components into larger assemblies; something that becomes necessary when build volumes are limited or when design size or geometry exceeds printer capabilities.
The use of joining and technique applied depends on factors like material compatibility, structural requirements, and end-use conditions. Adhesive bonding is among the most common methods, utilizing specialized adhesives designed for specific materials and applications. Mechanical fastening through screws, nuts, and bolts, or snap-fit connections provides another reliable option. For certain thermoplastic materials, welding techniques like ultrasonic or hot plate welding can create seamless joints by partially melting and fusing components together.
Proper surface preparation and alignment are critical in any case. Strong, durable joints ultimately form a foundation for reliable assemblies.
Sanding, Smoothing, and Polishing
These next tasks go hand-in-hand with support removal. Both steps of post-production address surface-level imperfections through specialized sanding techniques, abrasive tools, and polishing compounds. The distinction lies in extensity and purpose. Where supports are typically distributed strategically around a model frame - and therefore only call for attention to specific areas - sanding, smoothing, and polishing usually apply to all surface areas.
Here's a high-level summary of how each process works:
Sanding
Surface finishing begins with coarse sanding. Progressively finer grits of sandpaper (starting around 80 grit and moving up to 220 grit or higher depending on desired smoothness) are used in sequence to remove imperfections created by layer lines, support marks, and other printing artifacts. The initial sanding phase establishes a baseline surface texture that subsequent steps can refine further.
Smoothing
Most ABS printing projects usually involve some degree of smoothing. The process is similarly employed to remove layer lines, just in a different, usually touch-free way. Rather than manually abrased, printed parts are exposed to vaporized solvents like acetone, which temporarily dissolves the outer layer of plastic, allowing it to reflow and create a smoother surface.
Polishing
Designs with high gloss or mirror finish requirements undergo final polishing to achieve optimal surface characteristics. This step builds upon previous sanding and smoothing to create an exceptionally refined finish that meets specific aesthetic and functional requirements. It can be accomplished through mechanical buffing with specialized compounds and tools or through vapor polishing for compatible materials.
Priming, Painting, and Coating
Priming, painting, and coating hold equal aesthetic and practical value in 3D printing. These surface treatments serve multiple purposes beyond visual appeal, including protection against environmental factors, enhanced durability, and improved functionality.
Priming sets the basis for subsequent coatings by filling minor imperfections. Paint can then be applied to achieve specific color requirements or visual effects. Finally, specialized coating imparts properties like chemical resistance, UV protection, or electrical conductivity to the base material depending on its intended use. For instance, parts exposed to harsh environments might require multiple layers of protective coating, while decorative pieces might focus more on aesthetic finishes.
Even in an age of automated craftsmanship, finishing touches make all the difference in product excellence. Every manufacturer can benefit from learning about post-processing — specifically how and where it has the capacity to enhance the aesthetic perfection, functional reliability, and overall value of 3D printed parts they make.