Several ways of surface treatment of injection molded parts

Generally speaking, injection molding is all that you need to produce finished components. Once manufactured, parts with the correct color can be assembled with other parts to complete the product. However, the quality of injection molded parts can be further improved by surface beautification.

There are several reasons why manufacturers prefer surface beautification of injection molded parts. The most common is to increase the cosmetic value of the product, which can make it more desirable to customers.

Sometimes, surface beautification may be necessary to meet functional requirements, such as improving the wear strength or scratch resistance of the part.

So what are some common ways ZHXTOYS can do to beautify injection molded parts? Let’s find them here.


Overview: Hot stamping, commonly known as “hot gold”, mainly for silver or gold tags, is a special printing process without ink. It is carried out with the help of certain pressure and temperature.

The stamping machine is mounted on the stencil so that the printed materials and hot foil get transferred to the surface of the stamped printed materials in a short period of time under mutual pressure, the metal foil or pigment foil.

Features and Applications: This printing method is used throughout almost all areas of the plastics processing industry for its scratch resistance, abrasion resistance, and peel resistance. It is also used for decorative purposes in addition to important text tips and instructions for printing. Today’s embossed patterned films have excellent abrasion and scratch resistance, as well as extremely high physical and chemical resistance.

Process flow: The stamping process can be divided into four steps:

    • Contact between the stamping foil and the substrate
    • By heat and pressure, the transfer layer is transferred to the surface of the substrate
    • Removal of pressure and peeling off of the polyester film;
    • Feeding the stamping foil and replacing it with the substrate to be stamped.

Pad printing

Overview: Pad printing is an indirect concave head printing technology. It has become important to a variety of object surface printing and decoration methods. When pad printing is used, a soft (rubber-like) silicone tip is pressed onto the ink-coated printing block and then onto the surface of the product.

Features and applications: Suitable for printing onto irregular substrates (such as instruments, electrical parts, toys, etc.).

Process flow: 1. Put the ink into the gravure plate; 2. Scrape off the excess ink; 3. Squeeze the surface to obtain the ink; 4. Transfer the ink from the surface to the surface of the molded product; 5. Clean the surface and the layout (if necessary).

Screen Printing

Overview: Screen printing is a very old printing method invented by the Chinese 2000 years ago. The basic principle of its printing is – a part of the screen printing plate mesh passes through the ink and the rest of the plate on the mesh is blocked so that it can not pass through the ink, thus forming a blank on the substrate.

Features and applications: This method can be used for flat and cylindrical surfaces. Pad printing is suitable for small area printing, and large area printing. It can also be used for screen printing.

Process: Photochemical plate method is the most commonly used method for screen printing.

    • The screen is taut on the screen frame, and then coated with photopolymer on the network, forming a photographic plate film
    • Thereafter, the sun map base plate is placed together on the plate film sun, by exposure and development. The plate does not need to be inked with part of the light to form a cured plate film. The mesh is sealed when printing and the plate along the inked part of the mesh is not closed.
    • When printing in one end of the screen printing plate poured into the ink, ink in the absence of external force will not leak through the mesh hole in the substrate. When the squeegee with a certain tilt angle and pressure scraping ink, the ink through the screen plate is transferred to the substrate under the screen, to achieve image reproduction.

Water transfer printing    

Overview: Water transfer printing is a type of printing that uses water pressure to polymerize the transfer paper/plastic film with colored patterns. There are two types of water transfer printing, one is the water label transfer technology, and the other is the water draping transfer technology.

The former mainly completes the transfer of text and photo patterns, while the latter tends to complete the transfer on the entire product surface.

The overlay transfer technology uses a water-based film that dissolves easily in water to carry the graphics. Because of the excellent tension of the water-based film, it is easy to wrap around the surface of the product to form a graphic layer, giving the product surface a very different appearance, just like spray paint.

Features and applications: The biggest advantage of water transfer printing is that it can form a layer of natural or other desired pattern color without creating seams on the product with the complex appearance of concave and convex.

Moreover, its adhesion effect is not affected by the product material, while also avoiding the general layout of the printing of false position. Also, in the printing process, since the product surface does not need to contact the printing film, you can easily avoid damage to the product surface and its integrity.

Process: The process is as follows:

    • Film printing is done on the polymer film with a variety of different patterns
    • Spray primer: many materials must be coated with a layer of adhesives, such as metal, ceramics, etc. If you want to transfer different patterns, you must use a different base color, such as wood grain basic use of brown, coffee, earthy yellow, etc., stone grain basic use of white, etc.
    • Film Stretching: so that the film can be printed on the surface of the product and its integrity.
    • Film extension: let the film lay flat on the water surface and leave the film to stretch flat.
    • Activation: special solvent (activator) to make the pattern of the transfer film activation into the ink state.
    • Transfer printing: use water pressure to print the activated pattern on the printed object.
    • Washing: the impurities remaining in the printed workpiece will be washed with water.
    • Drying: It is workpiece drying, where the temperature depends on the material and melting point of the vegetation.
    • Spray paint: sprayed with transparent protective paint to protect the surface of the object to be printed.

UV transfer printing

Overview: The UV transfer process is also known as the UV infusion process or UV coating process. It uses UV transfer glue and metal non-stick characteristics. All kinds of cell phone ultra-thin button effects through the UV transfer process to PET, PMMA, or PC sheet, to make a variety of effects, including CD pattern, brushed pattern, weave pattern, sandblasting pattern, leather pattern, 3D surface, illusion effect, cat’s eye effect, matte surface, high gloss surface effects, etc.

Features and applications: With the advantages of ultra-thin, high hardness, high abrasion resistance, high solvent resistance, and exquisite appearance, this printing method is used in the 3C industry, various remote control buttons, home appliance control panel components, ceiling decorative pieces, etc.


    • Mold opening: The mold is to be made with the effect of UV transfer and positioning pillar and printing ink positioning holes (to make the transfer mold)
    • Transfer: The UV glue will be printed on the transfer mold by screen printing
    • Press together: The PC sheet to the transfer mold, and then use the glue stick to press the sheet tightly
    • Light solid: The sheet and the transfer mold are placed into the light solid machine for light solid
    • Demold: Take out the transferred products from the mold and put them in the designated position (the process is finished).


Overview: IML stands for the in-mold insert molding. The surface is a layer of hardened transparent film, the middle is the printing pattern layer, and the back is the plastic layer.

Because the ink is sandwiched in the middle, it can make the product prevent the surface from being scratched and resistant to friction and can keep the color vivid and not easy to fade for a long time.

It can realize matte surface, leather grain, wood grain, and various 3D patterns, but the outermost layer is film material, so the grain is not tactile.

Features and applications: It has a variety of applications and can be used in the short film production cycle, in expressing multiple colors. Patterns and colors can be changed at any time during production.

Moreover, it has excellent scratch resistance. IML production batch quantity is very flexible and suitable for multi-species small quantity production. Currently, IML is developing towards a variety of innovations, such as antibacterial, automatic repair of surface scratches, in-mold injection of real cloth, pearlescent effect, 3D texture, etc.

Process flow: It is mainly divided into three major steps: printing, molding, and film injection.

    • Cutting material: cut the rolled film into square blocks of the designed size for the printing and molding process.
    • Plane printing: It is done according to the requirements of the icon, text manufacturing into film network, printing icons, and text on the cut film square blocks.
    • Ink drying fixed: The printed film square is placed in a high-temperature oven
    • Apply protective film: To avoid blurring the surface of the printed film when punching the positioning holes, sometimes it is necessary to apply the single or double-layer protective film
    • Punching positioning holes: The positioning holes of thermoforming must be punched accurately. Thermoforming (high pressure or copper mold).
    • After heating the printed film, use the high-pressure machine or copper mold to form the film in preheated condition.
    • Cutting peripheral shape: Cut off a scrap of the formed three-dimensional film
    • Material injection: Put the film with the same three-dimensional shape as the front mold after forming onto the front mold to inject the finished IML product.

The above six are the most common surface treatment methods used for the popularity of our injection molded products. There are many more such as flock coating, metal spraying, spraying, laser engraving, IMR, and so on.

The lack of introduction does not mean that ZHXTOYS is not able to do it, but for baby products, the above six are the most applicable and can best meet the needs of customers who need to change the surface.

That’s all about the article. If you have any questions, you can contact us. We have 24-hour professional staff to match the service.

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