1. Review of Metal 3D Printing Technology
Metal 3D printing, sometimes referred to as metal additive manufacturing, is a technique whereby three-dimensional things are created by layer-by-layer stacking of metal powders or wires. Usually, its working idea is to melt metal powders or wires and stack them layer by layer using high-energy lasers or electron beams, therefore generating the necessary complicated structure. Particularly appropriate for making products with complicated geometric forms and internal structures, metal 3D printing offers more design freedom, material use, and production efficiency than conventional casting, forging, and cutting methods.
Metal 3D printing technology is extensively applied in the automotive sector to produce functional and ornamental elements, as well as engine components, chassis parts, body structural components, etc. These components often require great strength, high toughness, corrosion resistance, and exceptional surface quality. But while metal 3D-printed parts are being made, things like the stacking effect and thermal stress can cause surface problems like high roughness, high porosity, and surface flaws that need to be fixed later to make them work better..
There are two methods for surface treatment in metal 3D printing.
Technology in precision machining
One of the techniques usually utilized for the surface treatment of metal 3D-printed objects is precision machining. Mostly comprising sophisticated techniques including hand polishing, sandblasting, CNC grinding, form adaptive grinding, laser polishing, and chemical polishing.
Although hand polishing can give components' surfaces exact treatment, the quality mostly depends on the operator's experience; low repeatability and consistency and significant labor and time expenses define the quality.
Using high-speed airflow to sprinkle abrasive particles over the surface of parts is called sandblasting. This method gets rid of surface dirt, oxide coatings, and small flaws. Although this approach is appropriate for polishing and cleaning the outside of components, it is not easily accessible for processing those with intricate and porous inside surfaces.
Numerical control grinding is the method of precisely grinding parts using numerical control equipment, fit for surface treatment of complicatedly shaped objects. CNC grinding still presents major difficulties, meanwhile, for complicated structural components with high surface quality requirements.
On free-form surfaces, a novel technique called shape adaptive grinding is used to machine challenging-to-machine materials. Free-form surface polishing of hard metals such as titanium alloys can be accomplished by utilizing spherical flexible grinding heads and other equipment, therefore attaining quite high surface smoothness.
Laser polishing is a technique used to lower the surface roughness of objects by melting their surface material again using high-energy laser beams. Although laser polishing can produce great surface quality, the equipment cost is costly and has not been generally encouraged in useful applications.
Chemical polishing creates a smooth surface by means of chemical reactions, which remove the micro-rough layer on the surface of components. Small additive manufacturing parts-especially those with hollow constructions-are suited for this approach.
2. Technology for chemical treatment
Chemical treatment methods like electroplating, chemical plating, electrophoretic coating, and others are used to improve the surface quality, corrosion resistance, and looks of 3D-printed metal objects.
Electroplating, in which the principle of electrolysis covers a layer of metal or alloy over a metal surface, while strengthening the adhesion between the coating and the metal, helps the corrosion resistance and aesthetics of the items to be improved.
Chemical plating is a technique that deposits a metal or alloy layer on a metal surface through chemical processes. Chemical plating may cover complicated-shaped items completely and does not call for an outside power source, unlike electroplating.
The technique of evenly coating particles on metal surfaces using electrochemical concepts is known as electrophoretic coating. Particularly suited for surface treatment of automotive body parts, this technique can create a corrosion-resistant and visually beautiful protective coating.
3. Technology in heat treatment
Heat treatment is the rapid cooling of a metal by heating it to a designated high temperature and therefore improving its mechanical qualities. Heat treatment in metal 3D printing helps remove internal stress and raise part hardness and wear resistance.
Eliminating internal stress: Factors include stacking effects and thermal stress, causing typically notable internal strains inside the pieces produced during the metal 3D printing process. These internal tensions can be removed by heat treatment, therefore enhancing the part's stability and service lifetime.
Heat treatment helps to change the microstructure within the metal, thereby improving its hardness and wear resistance. Parts in the automotive sector that must bear significant loads and friction especially depend on this.
4. Other creative strategies
Apart from the conventional surface treatment approaches discussed above, creative metal 3D printing surface treatment solutions have also surfaced in the automotive sector.
Abrasive flow machining is an internal surface finishing technique whereby a fluid carrying abrasive passes across the workpiece to smooth and polish rough surfaces. For fine machining jobs, including burr removal, surface polishing, and radial forming, this approach is especially appropriate.
Ion plating is a technique that involves the rapid impact of metal or non-metal ions through physical vapor deposition, resulting in the formation of a hardened layer on a metal surface. Particularly appropriate for items in the automotive sector that must survive demanding environments, this approach can greatly increase the hardness and corrosion resistance of metals.
Using laser or electron beams, powder bed fusion technology is a metal additive manufacturing method whereby metal powder is melted and, layer by layer, formed into parts. Particularly suited for manufacturing automobile parts with complicated surfaces and internal structures, this technology can attain exceptional surface quality.
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