Injection molding is an advanced plastic processing technology that is characterized by high efficiency, high quality, and high precision, and is widely used in various fields. With the continuous development and progress of technology, it is believed that injection molding technology will become more mature and perfect, providing better support and assistance for the development of various industries.

Injection molding is achieved through the use of injection molding machines and molds. First, add plastic raw materials (usually in granular form) into the barrel of the injection molding machine, and the barrel melts the plastic raw materials through a heating device. Then, the screw or plunger of the injection molding machine rapidly injects the melted plastic into the closed mold cavity under high pressure. The plastic is cooled and solidified in the mold, and then the mold is opened to take out the formed plastic product.

How to solve the problem of warping and deformation of plastic products after injection molding in Dalian?

1、 Optimize mold design

Cooling system design

Principle of uniform cooling: Reasonably design the cooling pipeline layout of the mold to ensure that all parts of the plastic product can be cooled evenly. For example, for plastic products with complex shapes, cooling pipes should be placed as close as possible around the thick walled parts of the product and areas that are prone to heat concentration. Computer aided engineering (CAE) software can be used to simulate the cooling process, predict possible temperature differences, and optimize the position and diameter of the cooling pipeline.

Cooling medium flow control: Adjust the flow rate of cooling medium (such as water) to achieve balance in the cooling speed of different parts of the mold. In the thick walled part of the mold, the flow rate of the cooling medium can be appropriately increased to accelerate the cooling speed and reduce the cooling difference with the thin-walled part.

Gate Design 

Gate position selection: The position of the gate has a significant impact on the warping and deformation of plastic products. The sprue should be set at the center or thick walled part of the plastic product as much as possible, so that the plastic melt can evenly fill the cavity and avoid shrinkage differences caused by uneven filling. For example, for flat plastic products, setting the sprue at the center of the plate can make the melt flow evenly in all directions, reducing warping and deformation.

Determination of Gate Quantity and Form: Choose the appropriate number and form of gates based on the shape, size, and structural complexity of the plastic product. For large or complex shaped plastic products, using multiple gates can make the melt filling more uniform. Different gate forms (such as side gates, point gates, hidden gates, etc.) can also affect the flow and filling method of plastic melt, and need to be selected according to specific situations.

2、 Adjust injection molding process parameters

temperature control

Tube temperature regulation: The appropriate tube temperature can ensure the uniformity and fluidity of the plastic melt. For different plastic raw materials, it is necessary to strictly follow their recommended processing temperature range for setting. If the temperature of the barrel is too high, the shrinkage rate of the plastic melt will increase, which can easily lead to warping and deformation; If the temperature is too low, it will affect the fluidity of the plastic and cause uneven filling. For example, when injecting polycarbonate (PC) plastic products, the temperature of the barrel is generally controlled between 260-320 ℃.

Mold temperature control: Properly increasing the mold temperature can reduce residual stress inside plastic products, thereby reducing the possibility of warping and deformation. However, excessive mold temperature can prolong the cooling time and reduce production efficiency. The mold temperature needs to be determined based on the characteristics of the plastic and the requirements of the product. For example, for some plastic products that require high appearance, increasing the mold temperature appropriately can improve their surface quality and reduce warping and deformation.

Pressure adjustment

Injection pressure control: Reasonably control the injection pressure to avoid excessive internal stress caused by high pressure in the plastic melt in the mold cavity. Excessive injection pressure can cause plastic products to warp and deform after demolding due to the release of internal stress. On the premise of ensuring that plastic products can completely fill the mold cavity, injection pressure should be minimized as much as possible.

Optimization of holding pressure and time: The function of holding pressure is to replenish plastic melt during the cooling and shrinkage process of plastic, reducing shrinkage. Properly adjusting the holding pressure and time can effectively control the dimensional accuracy and warping deformation of plastic products. If the holding pressure is too high or the time is too long, it will increase the internal stress of plastic products, leading to warping and deformation; If the holding pressure is too low or the time is too short, defects such as shrinkage marks may occur.

3、 Material selection and pretreatment

Choose appropriate plastic materials: Different plastic materials have different shrinkage rates and mechanical properties. When designing plastic products, plastic materials with low shrinkage and good thermal stability should be selected based on the product's usage requirements and molding process characteristics. For example, glass fiber reinforced plastic can improve the dimensional stability of plastic products and reduce warping and deformation.

Pre treatment of plastic raw materials: Drying treatment of plastic raw materials is very important. If the raw materials contain moisture, bubbles will be generated during the injection molding process, which will affect the quality of plastic products and may also cause warping and deformation. For some highly hygroscopic plastics, such as nylon, it is necessary to dry them thoroughly before injection molding to remove any moisture.

Injection molding has many advantages, one of which is high production efficiency. Injection molding is an efficient production method that can achieve continuous production through automated production lines, greatly improving production efficiency and speed. In addition, injection molding can also produce complex products, such as parts with rich details and complex shapes, which can meet the needs of various industries.

Different plastic materials have different melting temperature ranges. For example, the barrel temperature of polypropylene (PP) is generally between 180-280 ℃, while the barrel temperature of polycarbonate (PC) requires 260-320 ℃. Excessive temperature in the material barrel can cause plastic decomposition, while insufficient temperature can prevent the plastic from fully melting, affecting the quality of molding.