Surface treatment after 3D printing of metal|
By jett NG | 18 June 2021 | 0 Comments

Surface treatment after 3D printing of metal|

Surface treatment after 3D printing of metal


Appearance: color, pattern, logo, glossy lines (3D, 2D);


Texture: feel, roughness, life (quality), streamline and so on;


Function: hardening, fingerprint resistance, scratch resistance;


The following is a detailed introduction of various surface treatment technologies for metal 3D printed parts:


First, anodic oxidation

Anodic oxidation, the electrochemical oxidation of metals or alloys. The metal or alloy parts are used as the anode, and the oxide film is formed on its surface by electrolysis. Metal oxide film changes the surface state and performance, such as surface coloring, improve corrosion resistance, enhance wear resistance and hardness, protect the metal surface, etc. For example, aluminum anodizing, aluminum and its alloy in the corresponding electrolyte (such as sulfuric acid, chromic acid, oxalic acid, etc.) as the anode, under specific conditions and the action of external current, electrolysis. The anodic aluminum or its alloy is oxidized, forming a thin layer of aluminum oxide on the surface, the thickness of which is 5 ~ 20 microns, hard anodic oxidation film can reach 60 ~ 200 microns. Anodized aluminum or its alloy, improve its hardness and wear resistance, up to 250 ~ 500 kg/mm square, good heat resistance, hard anodized film melting point up to 2320K, excellent insulation, breakdown resistance voltage up to 2000V, enhance the corrosion resistance, in Ω = 0.03NaCl salt spray after thousands of hours without corrosion. The thin layer of the oxide film has a large number of microholes, which can absorb various lubricants, suitable for the manufacture of engine cylinders or other wear-resistant parts; Membrane microporous adsorption capacity can be colored into a variety of beautiful gorgeous colors.


Anodic oxidation benefits:


1. Anti-static. 2. Surface magnesium light. 3. The wear resistance.


Many small aluminum parts on semiconductor equipment are anodized in order to increase hardness and reduce wear.


Two, phosphating treatment


Phosphating is a common pretreatment technology, in principle should belong to the chemical conversion film treatment, mainly used in steel surface phosphating, non-ferrous metal (such as aluminum, zinc) parts can also be applied to phosphating.


Phosphating is a chemical and electrochemical reaction to form a phosphate chemical conversion film process, the formation of phosphate conversion film is called phosphating film. The main purpose of phosphating is: to provide protection for the base metal, to a certain extent to prevent metal corrosion; Used as a primer before painting to improve the adhesion and corrosion resistance of the paint film; It plays a role of antifriction and lubrication in metal cold working process.




1. Enhance the adhesion between the coating film (such as coating) and the workpiece.


2. Improve the corrosion resistance of the surface coating of the workpiece after coating.


3. Improve adornment.


Three, black processing


Blackening is a common means of chemical surface treatment. The principle is to produce a layer of oxide film on the metal surface to isolate air and achieve the purpose of rust prevention.


There are two common blackening methods: traditional alkaline heating blackening and late normal temperature blackening. But the blackening process at room temperature is not good for low carbon steel. Alkaline blackening subdivision, and there is a blackening and two blackening difference. The main components of blackening solution are sodium hydroxide and sodium nitrite. The tolerance of the temperature required to blacken is larger, about 135-155℃ can get a good surface, but the required time is some length.

Four, passivation treatment


Metal by oxidizing medium after treatment, its corrosion rate than the original untreated has a significant decline in the phenomenon called metal passivation. The passivation mechanism can be explained by the thin film theory, that is, the passivation is due to the interaction between the metal and the oxidizing medium, and a very thin, dense, well-covered passivation film can be strongly attached to the metal surface during the action. This membrane exists as a separate phase, usually a compound of oxygen and metal. It plays the role of completely separating the metal and corrosive medium, prevent the direct contact between the metal and corrosive medium, so that the metal basically stops dissolving and forms blunt to achieve the effect of preventing corrosion.



Passivation treatment is the last process step in chemical cleaning, is a key step, its purpose is to prevent corrosion of materials. Such as the boiler after pickling, water washing, rinsing, the metal surface is very clean, very active, very vulnerable to corrosion, so it must be immediately passivation treatment, so that the cleaned metal surface to generate protective film, slow down the corrosion.


Five, the laser carving

Radium engraving, also known as laser engraving or laser marking, is a process of surface treatment using optical principles. Radium carving is a kind of marking method which makes use of high energy density laser to locally irradiate the workpiece, so that the surface material will vaporize instantaneously or undergo a chemical reaction of color change, so as to leave a permanent mark. The radium carving can be used to type all kinds of words, symbols and patterns, and the character size can range from millimeters to microns. With this technique, there are no scratches, the surface of the object remains smooth, and the writing does not wear out.


Process (implementation method) :

Radium engraving refers to laser engraving, which leads to the chemical and physical changes of the surface material by the light of the laser beam, or burns part of the material by the light energy, showing the graphics and words needed to be etched; According to the different carving methods can be divided into dot matrix carving and vector cutting.

The process of radium engraving is as simple as printing on paper using a computer and printer; Can be designed in CorelDraw and other graphics processing software, scanning graphics, vectorized graphics and a variety of CAD files can be easily "printed" to the engraving machine. The only difference is that printing applies toner to paper, while laser engraving applies laser light to wood products, subgrains, plastic sheets, metal plates, stone and almost any other material.


Six, electrophoretic paint

Electrophoresis process is divided into anode electrophoresis and cathode electrophoresis. If the coating particles are negatively charged, the workpiece is the anode, and the coating particles are deposited into a film in the workpiece under the action of electric field force, which is called anode electrophoresis. Conversely, if the coating particles are positively charged and the workpiece is the cathode, the coating particles deposited on the workpiece into a film is called cathode electrophoresis.



Electrophoresis Application:



It can be divided into anode electrophoresis paint and cathode electrophoresis paint.


The anodic electrophoretic paint has anodic acrylic acid, mainly used in aluminum products, aluminum oxidation with anodic electrophoretic paint protection, gloss between 50-90 degrees, thin paint film, widely used in the aluminum profile industry. Cathodic electrophoresis paint can be divided into: epoxy electrophoresis paint, acrylic electrophoresis paint and polyurethane electrophoresis paint.


Seven, drawing

Wire drawing process is a kind of metal working process. In metal pressure working. The metal is forced through the mold under the action of external force, and the cross-sectional area of the metal is compressed, and the required shape and size of the cross-sectional area of the technical processing method is called the metal drawing process. Make it change shape. The size of the tool is called a drawing die. Such as the cable industry will be 8mm copper rod with copper drawing machine, through a group of (5~8) from large to small drawing mold, the copper rod into copper wire, such as 3.5mm, 2.0mm, etc..

Wire drawing is a method of reciprocating motion of the wire drawing cloth and rubbing back and forth on the surface of the workpiece to improve the surface finish. The texture of the surface is linear. Can improve the surface quality, cover the surface slight scratches.

The role of wire drawing:

The surface of the metal plate has the characteristics of rust resistance, oxidation resistance, scratch resistance, chemical reagents and smoke resistance. In appearance, due to the special bright surface of the product itself, in order to avoid the loss of luster due to friction, it is recommended to use in the horizontal surface with less friction, or the general vertical plane. In addition, it is recommended to use in dry, or not often wet, moisture is not too heavy, to maintain the stability of the product. Metal surface drawing can well cover up the defects of mechanical grain and mould in production.


Eight, CD


CD grain is the application of precision CD grain machine in the metal surface to remove materials and get a similar effect with CD disc grain, its grain spacing is according to the appearance of the product size effect. It is widely recognized in the industry that CD pattern is a kind of high grade surface treatment technology for metal surface.


High-quality CD grain processing must have the following five elements:


1. High precision CD printing machine.


2. Scientific product processing fixture.


3. Trained process operators.


4. Choose reasonable machining tools.

5. Proper cooling plan.

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