The plastic resin is melted in the injection molding machine and then injected into the mold, where it cools and solidifies into the final part. 

Plastic products are lightweight and inexpensive, and can be produced massively and fast. It is easier to form structures and perform surface treatment on plastics than on the metal. So it has been a substantial replacement of metal or other materials products, and commonly used on a variety of daily commodities in daily life.

Plastic polymers can be divided into two main categories:

1. Thermoplastics: The curing process is completely reversible. It is recyclable and reusable, but with poor heat resistance. According to the function, it can be classified as general plastics, engineering plastics, elastomers. Such as: PET bottle, acrylic, etc.
2. Thermoset plastics: Plastics which become irreversibly hard on heating and not easy to recycle. It is more heat resistant and weather resistant than thermoplastics. Such as: tires, dishes, melamine tableware.

There are many kinds of plastic materials on the market. In order to meet the different product functions and applications, a variety of plastic material are gradually developed a variety of plastic materials. As long as you detail the function and the intended use of the product, we can recommend you the most suitable material. The main principles of material selection are: application, function, environment and price.

Common defects include short shot, knit lines, surface sinks (shrinkage), surface flow marks, discoloration (debris), flash, bubbles, bubbles,  stick on core/cavity, and warpage/deformation, etc.

The deformation/warping of the plastic injection molded products  is a very difficult issue. It should be prevent mainly from the initial mold design and plastic material selection. The effect of adjusting molding parameters is very limited. Common causes of deformation and solutions are as follows:

1. Residual stress: Deformation caused by molding pressure can be eliminated by reducing the pressure, increasing the temperature of the mold and material, or by annealing.
2. Cooling unevenly: If the cooling is uneven, deformation may occur. It can be solved by adjusting the mold temperature to the average temperature, or setting different mold temperature and extend the cooling time according to the degree of warpage.
3. Improper ejection from the mold: The uneven ejection force causes deformation. It can be solved by increasing the draft angle, or adding ejectors, or extending ejection area to improve the ejection system.
4. Sink deformation: Sink deformation after molding, which is generally structural deformation. In such case, it is necessary to consider product design change. The most important thing is to make the overall material thickness even.
5. Product structure deformation: Deformation due to this cause is the most difficult problem. Choose different solutions depending on the product development stage and requirements.
   • Before mold development: Use CAE software for deformation analysis in advance. It allows design changes to reduce deformation before product development starts.
   • After mold development: Analyze of the overall deformation trend according to the measurement data, and then proceed mold correction according to the data of different areas of mold.
   • Without affecting the mold structure and product function, it is also possible to use auxiliary fixtures for product correction.