产品设计与工艺：塑料表面处理工艺

The purpose of surface treatment is to meet the corrosion resistance, wear resistance, decoration or other special functional requirements of the product, also known as secondary processing.

1. Surface machining

Advantages:

Make the surface smooth, bright and beautiful.

1.1. Scrub

Frosted plastic generally refers to plastic film or sheet. When calendering, there are various lines on the roller itself, and the transparency of the material is reflected by the different lines.

1.2. Polishing

Polishing refers to the processing method of using mechanical, chemical or electrochemical action to reduce the surface roughness of the workpiece to obtain a bright and flat surface.

The principle is the same as the principle of shoe shine. Use paraffin oil and kerosene to dip the toothbrush evenly on the plastic, evaporate for a day, pull it left and right with silk such as socks, wipe it back and forth on the plastic surface, and then dry it.

2. Surface plating treatment

Advantages:

Decoration, beautification, anti-aging, corrosion resistance.

2.1. Painting (spraying)

Plastic spraying is to spray paint on the surface of plastic to ensure the beauty and physical properties of plastic.

Effects: coloring, obtaining different textures, preventing plastic aging, corrosion resistance.

Plastic spraying process:

Annealing → degreasing → eliminating static electricity and dust removal → spraying → drying

Powder spraying: spray plastic powder on the surface of the workpiece under the condition of an electrostatic field, and then cure it into a protective layer at high temperature;

Spraying: Spray the alloy powder to the surface of the workpiece by heating to form a wear-resistant layer or fill the worn part;

Spray paint: spray the paint evenly on the surface of the workpiece with compressed air.

Spray paint is oil spray, divided into ordinary spray paint, UV paint, PU paint, rubber paint (hand paint).

Because UV paint is more environmentally friendly than PU paint, PU paint is gradually replaced by UV paint.

2.2. Printing

Plastic printing refers to a process in which the desired pattern is printed on the surface of plastic parts.

It can be divided into screen printing, curved printing (pad printing), hot stamping, penetration printing (transfer printing), and etching printing.

2.2.1. Screen printing

The printing plate is in a mesh shape, and the ink on the printing plate is leaked from the through hole of the layout to the substrate under the extrusion of the ink scraper during printing.

Usually silk mesh is made of nylon, polyester, silk or metal mesh.

Plastic screen printing applications:

1) ABS plastic

2) Appearance of plastic parts of electronic products

3) Plastic signage

4) Soft and hard plastic parts

5) Instrument panel

6) Color polyester signage

Screen printing:

The traditional plate making method is manual, and the photochemical plate making method is commonly used in modern times.

In this plate-making method, the screen is used as a support, the screen is stretched on the screen frame, and then the screen is coated with photosensitive glue to form a photosensitive plate film, and then the bottom plate of the positive picture is tightly attached to the plate film. After exposure and development, the part of the printing plate that does not need to be inked is subjected to light to form a cured plate film, and the mesh is sealed, and ink is not permeable during printing; the mesh holes of the part of the printing plate that needs to be inked are not closed, and the ink is transmitted during printing, and ink is formed on the substrate.

2.2.2. Pad printing (curved printing)

As a printing method for printing characters or patterns on the surface of plastic molded products, curved printing methods are often used.

Curved printing refers to using a piece of flexible rubber to print the characters and patterns that need to be printed to the surface of plastic molded products containing curved or slightly concave and convex surfaces.

The principle of curved surface printing is to first put the ink into a gravure engraved with characters or patterns, then copy the characters or patterns onto the rubber, and then use the rubber to transfer the characters or patterns to the surface of the plastic molded product, and finally through heat treatment or ultraviolet light irradiation and other methods to cure the ink.