Before applying a finish the part needs to be post processed, this is where the support structure is carefully removed and any surface zits and blobs are removed. A deburring tool can also be used to remove any sharp points such as holes and edges that may have resulted from the printing process.
Some designs may have been split up into multiple parts, these parts need to be assembled together either with a self locking mechanism designed into the parts or adhesive suitable for the printed plastic. Cleverly designed components can use the materials flex properties to snap around a piece of geometry. Superglue is a good choice of adhesive for rigid printed components made from PLA, PETG or ABS and can be sanded down if needed. Surfaces for superglue need to be clean and free from dirt and dust. Other adhesives that can be applied include epoxy, hot glue and acetone.
Some low temperature materials allow for reheating with a hot air rework tool, this allows for blobs and stringing to be removed from a 3D print, it also allows for reshaping on smaller areas. Reheating can also be used to smooth out uneven print surfaces removing imperfections.
Due to the ball-like profile of the extruded material on a FDM printer, the perimeter of a 3D printed object will feel uneven, the walls can be sanded down to a smooth finish. 600 grit sandpaper can be used to remove the initial roughness out of the material, then changing to a higher grit sandpaper such as 1200 grit to smooth the surface out. Sanding on smaller surfaces may prove difficult and therefore a small needle file may be beneficial to clean up design details. For surfaces that exhibit large gaps, automotive car body filler is a 2 part mixture that can be used to fill these gaps, then dried and sand down to a smooth finish. Aerosol filler primer can be used as an undercoat in combination with wet and dry sandpaper to produce a good base layer prior to painting.
Paint coatings and special coatings can be applied over a 3D printed part, a good surface is required to be painted upon such as one that has been sanded and primed using 2 thin coats of primer. Automotive paints come in a variety of colours and finishes, these are most suitable to be applied in several thin coats on a primed 3D printed object. Other special coatings such as anti-static coatings, metal-effect coatings, insulating plastic coatings and clear lacquers can be applied to 3D printed objects..