Manual Post treatment (Part 2)

In the last issue, we talked about the surface treatment processes that are often used in the post treatment of handboards: grinding, sandblasting, polishing, spraying, powder spraying, and UV spraying.

Then today we will talk about other post-treatment surface treatment processes: printing, radium carving, electroplating, oxidation, blackening, wire drawing and phosphating. (Oxidation, blackening, wire drawing and phosphating are only applicable to metal parts)

1 Printing

(1) Silk screen printing: part of the mesh of the screen printing plate can pass through the ink and miss printing to the substrate; The mesh of the rest of the plate is blocked and cannot pass through the ink to form a blank on the substrate. The mesh of the part to be inked on the printing plate is not closed. During printing, the ink passes through and forms ink marks on the substrate. During printing, ink is poured into one end of the screen printing plate. The ink will not leak on the substrate through the mesh without external force. When the ink is scraped by the ink scraper with a certain angle and pressure, the ink is transferred to the substrate under the screen through the screen to achieve image replication. (The printed pattern is convex)

Advantages of silk screen printing:

A. Low cost and quick effect;

B. Suitable for printing on irregular substrate surface;

C. Strong adhesion and good inking performance;

D. The ink layer is thick and three-dimensional;

E. Strong rotation resistance and good color formation;

F. Wide range of printing object materials and large printing format.

(2) Transfer printing (curved surface printing): It refers to printing the words and patterns to be printed on the surface of plastic molding products with curved or slightly concave convex surfaces with a piece of flexible rubber. Transfer printing is to put the ink into the intaglio with carved words or patterns, then copy the words or patterns onto the rubber, transfer the words or patterns onto the surface of plastic molding products with rubber, and finally solidify the ink through heat treatment or ultraviolet light irradiation.

Radium carving: Radium carving is also called laser carving, which is a process of surface treatment using optical principles. For example, to build a keyboard, the characters on it are blue, green, red and gray, and the key body is white. When laser engraving, first spray the corresponding colors on the blue characters, green characters, red characters, and gray characters, so that it looks like there are blue keys, green keys, and other keys, and then spray a layer of white color on the whole. This is a whole white keyboard, and all blue and green characters are wrapped under it. Then, the film is made of laser technology and the key map submitted by the industrial designer. The white oil on the film is carved out to show blue and green buttons.

Limitations of radium carving:

(1) Radium carving depth: AL is 0.1mm, plastic paint coating: 0.2-0.3mm, iron and other metals up to 0.08mm;

(2) The limit surface area of the radium carving is 100X100mm. If it exceeds 100X100mm, the radium carving needs to be spliced. The connection position is not beautiful and the connection trace is obvious.

(3) White and near white colors cannot be carved, and characters carved from curved radium are prone to deformation.

3 Electroplating: Electroplating is to make metal adhere to the surface of an object by means of an electrode passing through an electric current. The purpose is to change the characteristics or dimensions of the surface of an object. Electroplating is generally divided into wet electroplating and dry electroplating.

The wet method is commonly referred to as water plating, while the dry method is commonly referred to as vacuum plating. Water plating is to generate ion replacement and attach the coated metal to the surface of the plating piece through the electrode method. The vacuum plating is to use high voltage and large current to make the coated metal vaporize into ions in a vacuum environment and then evaporate to the surface of the plating piece. The water plating adhesion is good, and no other treatment is needed later. The vacuum plating adhesion is poor, Generally, PU or UV.PC shall be made on the surface and cannot be plated.

Duplicates cannot be water plated, but can only be vacuum plated. The color of water electroplating is monotonous. Common water electroplating includes chromium, nickel, gold, etc., while vacuum electroplating can solve the problem of colorful Before water plating, the surface effect of the workpiece must be polished to 1500-2000 abrasive paper, and then water plating can be carried out after polishing. Therefore, water plated workpieces are generally very expensive. The grinding effect of vacuum plating can be slightly less than 800-1000 abrasive paper, so vacuum plating is relatively cheap

4 Oxidation: The oxidation treatment of metal is to form a protective oxide film on the metal surface by acting with oxygen or oxidant to prevent metal corrosion. Oxidation is divided into chemical oxidation and electrochemical oxidation (i.e. anodic oxidation).

(1) The oxide film produced by chemical oxidation is thin, with a thickness of about 0.3-4um, porous, good adsorption capacity, soft but not wear-resistant, and good conductivity. It is suitable for occasions with shielding requirements, and can be painted with various colors. It has good adsorption capacity, and can be painted with various colors. Re painting on its surface can effectively improve the corrosion resistance and decoration of aluminum products.

(2) The oxide film produced by anodic oxidation is relatively thick, with a thickness of 5-20 v m in general, and the thickness of hard anodic oxide film can reach 60 – 2500 vm. It has high hardness, good abrasion resistance, good chemical stability, good corrosion resistance, good adsorption capacity, good insulation performance, strong thermal insulation and resistance, and can be used in various colors. To sum up, the oxide film formed on the surface of aluminum and aluminum alloy after chemical oxidation treatment, especially after anodic oxidation treatment, has good characteristics of protection and decoration. Therefore, it is widely used in aviation, electrical, electronic, mechanical manufacturing and light industry. (It can only be oxidized on aluminum or aluminum alloy. Generally, aluminum alloy is oxidized with imported 6160)

5 Blackening: surface blackening treatment, also known as bluing. There are two commonly used methods for blackening treatment: traditional alkaline heating blackening and late room temperature blackening. The protective film obtained by blackening is black, which improves the corrosion resistance and mechanical strength of the metal surface, and can also be used as a good bottom layer of the paint. (The stainless steel cannot be blackened, and the blackening effect of iron is the best)

6 Wire drawing: wire drawing treatment is a surface treatment method that forms lines on the workpiece surface by grinding products to achieve decorative effect. Wire drawing can well reflect the texture of metal materials, and can make the metal surface obtain non mirror metallic luster. According to different surface effects, it can be divided into straight silk (hair texture) and messy silk (snowflake texture). According to the requirements of wire drawing effect and the size and shape of different workpiece surfaces, wire drawing can be divided into manual wire drawing and mechanical wire drawing.

Common manual wire drawing is mostly used for 3M company’s industrial cleaning cloth. The quality of silk patterns is subjective. Each user has different requirements for surface lines and different preferences for line effects. Therefore, it is necessary to have a drawing template to produce a satisfactory effect. The circular arc (the junction between the curved surface and the straight surface is very ugly, and the wire drawing is uneven) and the paint surface (the metal color surface can be used to draw fine silk lines) should not be drawn