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Full analysis of insert injection molding technology

Insert injection molding is an important technology widely used in the field of plastic processing. There are many types of processes, each with its own characteristics. In the large family of injection molding processes, insert injection molding is quite special.

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Full analysis of insert injection molding technology

Injection molding is an important technology widely used in the field of plastic processing. There are many types of processes, each with its own characteristics. In the large family of injection molding processes, insert injection molding is quite special.

What is insert injection molding? Simply put, during the injection molding process, a pre-prepared metal or other material insert is placed in the mold, and then molten plastic is injected. After the mold is opened, the insert is tightly buried in the plastic by the cooled and solidified plastic. The plastic and the insert are firmly combined to form a complex and delicate integrated part or product with inserts such as threads and electrodes. It is also called “rubber injection molding” in China.

What is insert injection molding

What is insert injection molding

Process flow of insert injection molding

In the insert injection molding process, the injection molding machine is usually only a part of the whole system. The insert usually needs to be oriented first, which can be done with a vibration table. Then, the insert is placed in the mold by the robot end-of-arm tooling (EOAT), usually with the help of a pre-positioning device. When it comes to the finished part stage, ejection positioning is the most important step, and the repeatability of the injection molding machine’s mold opening action is crucial here. After the insert is installed in the mold, it is fixed in a vacuum state or by mechanical means (such as using a slide). While the insert is inserted, the previous finished part is ejected .

Insert injection molding process

Insert injection molding process

When insert molding, the placement of the insert in the mold can also be done manually, but this will greatly increase the injection molding cycle and reduce the production efficiency of the injection molded product. It is only suitable for small batch production or products with complex structures. Automated placement is a better choice for mass production, which is conducive to reducing manual errors, improving efficiency, shortening the injection molding cycle and improving product reliability.

In this technology, the integrated operation of the injection molding machine, mold and automation device plays the most important role. Combining the injection molding machine with a robot with automatic clamping inserts, an insert product arranging device and other equipment, many insert injection molding processes can achieve automated production, reduce manual errors and improve product quality.

The vertical injection molding machine is equipped with a rotating worktable, a mobile worktable and a tilting worktable, etc., which can easily achieve insert injection molding. Since the mold face is facing up, it is easy to place the insert. If the lower template is fixed and the upper template is movable, combined with a belt conveyor and a robot, it is easy to achieve fully automatic insert injection molding. However, the more advanced horizontal injection molding machine can also achieve insert molding well, which is no different from the vertical injection molding machine.

The vertical injection molding machine is generally open-ended around the clamping device, which is easy to configure various automation devices. It is suitable for processing inserts, embedded parts, connectors, etc. The injection molding precision is higher than that of the horizontal injection molding machine, the price is relatively cheap, and it is easy to load and unload, which is very suitable for small batch production.

Advantages and disadvantages: There is no perfection, only more suitable

Insert molding has many characteristics and advantages! First of all, integration is the biggest feature of insert molding, which can achieve the perfect combination of the advantages of different materials, so that the product has both the lightness, elasticity and easy molding advantages of plastics, and the rigidity, strength and durability of metals.

Secondly, integrated molding integrates the insert and plastic into a single component, eliminating secondary processing steps such as welding and riveting, greatly shortening the assembly time and reducing labor and material costs, and improving production efficiency. Insert molding, which combines the insulation of plastics and the conductivity of metals, can enhance the functionality of the product. For example, in electronic and electrical products, it can achieve better electrical conductivity, magnetic conductivity, heat dissipation and other properties. Insert products are not limited to metals, but can also be cloth, paper, wires, glass, wood, coils, springs, nuts, electrical parts and many other types of items, providing unlimited possibilities for product design.

Characteristics and advantages of Insert molding

Characteristics and advantages of Insert molding

Designers can create novel shapes and structures more “imaginatively” according to product requirements .

Although insert injection molding has many advantages, it also inevitably has some disadvantages.

  • ◆ Technical difficulty: Insert injection molding has extremely high requirements for mold design, material selection, injection molding process, etc., and the technical threshold is relatively high.
  • ◆ Difference in thermal expansion coefficient: The thermal expansion coefficient of the insert is inconsistent with that of the plastic resin, which easily increases the internal stress of the final product, thereby causing the product to warp and deform (Figure 4). Inserts often require preheating or drying treatment to reduce internal stress.
  • ◆ High mold cost: The addition of inserts makes the mold structure more complex, and the mold precision requirements are extremely high. The initial mold production cost is relatively high, which is not very friendly for small batch production. How to reduce the mold cost has become a major problem in insert injection molding.
  • ◆ Long production cycle: The placement and adjustment process of inserts is relatively cumbersome, and improper operation is prone to waste, affecting production efficiency. This is also a major challenge facing insert injection molding technology.
  • ◆ Difficult quality control: Once defective products appear in insert injection molding, such as poor injection molding, missing inserts, poor positioning, etc., the entire product is often scrapped, which is costly.
  • ◆ The product recycling cost of insert injection molding is relatively high.

Application fields of insert injection molding

Insert molding utilizes the insulation of plastic resin and the conductivity of metal, and the molded products can meet the basic functions of electronic and electrical products. With the increasing complexity of industries such as electronic components, automobiles, and medical care, insert molding technology is shining in these fields .

The automotive industry has always been a loyal supporter of insert molding technology. Insert molding can improve the strength of parts, reduce weight, and help lighten automobiles. This technology is a powerful assistant for new energy vehicles.

Under this layout, direct contact between conductive parts may cause short circuits and cause safety hazards. Due to the limitation of the bottom space of the car, it becomes difficult to maintain a safe distance between components, and the bumps and collisions of the vehicle under harsh road conditions increase the risk of component displacement. The insert injection molding process has played its unique advantages in this field. It uses insulating injection molding materials to tightly integrate electronic components of metal materials, effectively isolate the possibility of short circuits, improve the high-voltage safety protection performance of the car, and shorten the distance between components, optimizing the overall layout .

Application fields of insert injection molding

Application fields of insert injection molding

In addition, when the vehicle is hit, the injection molding material can provide the necessary buffer to protect the electronic components from damage. The use of copper busbar inserts realizes the electrical connection between high-voltage components, greatly improving the integration and space utilization efficiency of high-voltage electrical systems such as batteries and high-voltage power distribution units (PDUs).

At present, the use of insert molding for automotive electronics has become the mainstream choice of the industry. Whether it is the motor controller, battery disconnect unit (BDU)/PDU power management module, or the bus  and inverter components , insert injection molding technology has achieved efficient, safe and compact integrated design, which marks a major advancement in automotive electronics manufacturing technology.

More and more sensors will be installed on electric vehicles. In addition, systems such as reversing cameras and remote starters were only equipped on high-end cars in the past, but this is no longer the case. As complexity increases, the demand for insert molding technology is also increasing.

At present, new energy vehicles are moving towards a new era of high integration and integration, and the design of electronic components in the car is becoming more compact. Insert molding technology, with its seamless fusion of metal and plastic, has brought an efficient solution to the new energy vehicle industry and has been widely used in the new energy vehicle industry. This technology not only significantly promotes the integration and simplification of automotive parts, helps companies cope with cost pressure in an increasingly competitive market, but also becomes a key driving force for the technological progress and market demand expansion of the entire automotive industry.

In the field of consumer electronics, the application of insert injection molding is extremely extensive, meeting the needs of electronic products for miniaturization, integration and high performance. For example, mobile phone antennas are a perfect example of the application of insert molding in this industry. Insert molding makes mobile phone antennas thinner and lighter, and the signal is stronger. Other examples include connectors, switches, sensors, etc.

Insert injection molding notes

Insert injection molding notes

In the field of medical devices, insert molding can be seen from simple medical devices to complex and sensitive medical devices such as sutures and implants. In addition, insert injection molding can also be used to produce some electronic equipment for the medical industry, such as the production of pipes, medical equipment components and dental instruments. Other applications include medical knobs, blades, surgical instruments and medical housings, etc.

In the field of aerospace, insert molding is mainly used for aircraft seats, luggage compartment latches, toilets, handles and user interface switches. In addition, sensors, valves, etc. are also often manufactured using insert injection molding. This process ensures the accuracy and reliability of components and meets the high performance and high precision requirements of the aerospace industry.

Insert molding is not the only process for combining plastic and non-plastic materials (others include two-color injection molding, welding, etc.). Its wide application in the fields of automobiles and consumer electronics is inseparable from the excellent performance of this process in terms of cost-effectiveness, part reliability and design flexibility. It can be said that the insert injection molding process is one of the most popular injection molding processes at present.

Future Prospects

The insert molding process has not been fully developed. With the continuous advancement of technology, we can expect insert injection molding to continue to develop in the future, including the application of new engineering plastics and more intelligent materials, higher sustainability and more efficient production processes.

With the rapid development of industries such as new energy vehicles and intelligent manufacturing, the demand for high-performance, high-precision and high-integration products is increasing, and insert injection molding technology will also usher in more development opportunities. With the development of intelligent manufacturing, the automation and intelligence of insert injection molding equipment will continue to improve. At the same time, with the continuous advancement of technology and the gradual reduction of costs, insert injection molding technology is expected to be applied and promoted in more fields.

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