Traditional plastic processing has gradually failed to meet our needs, that's why in-mold decoration (IMD) plays a big role. People like thin, short and light electronic products. We do care about environmental protection, giving rise to this technology.

IMD is an automated production process. Compared with traditional processes, IMD reduces production steps and parts, which not only saves time and cost of rapid production, but also improves product quality, increases image complexity, and improves product durability. It can be applied to design of product appearance.

IMD can finish printing, high-pressure forming, stamping and cutting on film surface, and finally combine with plastic to avoid manual working time and secondary operation process. It's good at the printing roller coating, such as backlight, multi-curved surface, imitation metal, wool processing, logical light pattern, rib interference, etc..

IMD can replace many traditional processes, such as thermal transfer, spraying, printing, electroplating and other appearance decoration methods. It's OK for products that require various color images, backlight, etc.

Of course, not all surface treatment for plastic can be replaced by IMD. IMD still has some bottlenecks on positioning accuracy, distance between special shapes and convex points, inverse relationship between tension and hardness, degree of drawing materials, etc.. For specific products, you should provide 3D drawing files for professional engineers.

Cracks

You can see cracks on IMD products. There are surface filiform cracks, micro cracks, whitening, cracking, and damage caused by the mucous membrane of parts and runners. Cracking is divided into demolding cracking and application cracking.

Cracks refer to the breakage of molded products when the mold is opened or ejected. Sometimes cracks occur when the product becomes brittle or has poor demolding properties. There are reasons and solutions of cracks of IMD products.

1. Machine

The plasticizing capacity of injection molding machine should be appropriate. If it is too small, the product will become brittle due to insufficient plasticization.

2. Materials

a. The material is not suitable for the processing, or the quality is poor. Contamination will also cause cracking.

b. There are too much recycled material, so the strength of the product is too low. It is easy to cause cracking.

c. Excessive humidity will cause a chemical reaction between the plastic and water vapor, which will reduce strength, and cause the ejector to rupture. Pay attention to the molding temperature of each material. The residence time should be shortened to reduce resin degradation, and the drying conditions should be strengthened to inhibit hydrolysis.

3. Mould

a. The main runner is sufficient to release the gate material at a later time and during solidification. It is easy to release.

b. For deep-bottomed products, the demoulding air inlet should be properly set to prevent the formation of vacuum negative pressure.

c. Use as few metal inserts as possible to prevent excessive internal stress caused by differential shrinkage between inserts and product.

d. The sprue bushing and nozzle joint should prevent the cooling material from dragging and causing the product to stick to the fixed mold.

4. Processing

a. Properly increase the mold temperature to make the product easy to demould, and properly reduce the material temperature to prevent decomposition.

b. Prevent cracking and plastic degradation due to welding marks. Otherwise, it would reduce the mechanical strength.

c. Use mold release agent appropriately, and take care to regularly remove aerosols attached to the mold surface.

d. Rapid and strong pulling of the product can easily cause demoulding and cracking, so the door opening speed and pressure should be adjusted appropriately.

e. Residual stress in the product can cause cracks. After the product is formed, internal stress can be eliminated by annealing and heat treatment immediately to prevent cracking.

f. Excessive processing pressure, too fast speed, too much filling, too long injection and holding time will lead to excessive internal stress and cracks.