The name suggests is a multi-color injection molding using two or more plastic members to achieve injection. Including generalized multicolor injection over molding, achieved by an ordinary injection molding machine, two-shot, multi-color injection molding is the use of a narrow multi-color injection molding machine, 2. Two or more different plastics are injection molded on the same machine, the most common one is the rotary injection molding machine.
Multi-color injection After years of development, is not limited to rotary molding machine, which has expanded the doors of many fixed branches, sandwich injection molding, multi-colored cube molds and injection of liquid silicone is also popular trend in recent years, the sandwich Injection molding to consume secondary materials, twin-screw is responsible for injection and independent pressure-holding, and thus improve cycle to reduce energy consumption. It is called the most environmentally friendly injection molding process; cube mold has unique advantages in efficiency, and is very suitable for thin walls such as bottle caps. products, there are products on the mass production of the excellent advantage; injection of liquid silicone, LSR as a combination of high temperature resistance, corrosion resistance and other excellent properties, and have the stability and accuracy of the molded parts and the like to bring excellent characteristics , Become a hot new product choice. Next, let's take a look at it:
Common forms of multicolor injection molding:
Vertical turntable
Wheel vertical (parallel radio station) injection molding machine is the most widely used two-shot injection molding machine, it can be sized large molded articles usually tonnage of 1500 tons, have certain requirements on the mold size and shape, can not exceed the loading Area.
In-mold rotation
After injection is completed, the holder of the core in the motor driven rotating mold, the preform is moved to the next position to complete the subsequent processing. Mold rotating in the toothbrush manufacturing art has a very outstanding advantage can improve production efficiency over 50% At the same time, it can complete the customization requirements of multiple colors and production packaging at the same time.
Horizontal turntable
The horizontal rotating (opposite) injection molding machine can form large two-color parts, such as TV frame, car sunroof, lamp cover, etc. The maximum tonnage can reach 1900 tons. The horizontal turntable, the biggest advantage is that it can produce large tonnage products. The process is unmatched by traditional carousel equipment. It is widely used in the field of automobile manufacturing.
Monochrome injection molding machine produces two-color products
Monochrome injection molding machine is the earliest and most basic two-color injection molding application. The principle is very simple. First, the first semi-finished product will be produced. After the production is completed, the front semi-finished product will be coated on the second set of molds. The advantage is production flexibility. Large, the investment in the machine is reduced, the disadvantage is that it will increase the inventory of semi-finished products. It is easier to put into production for small injection molding plants that are just starting out, but this process will gradually be eliminated in the environment of increasing automation.
Linked robot
The two injection molding machines are connected by a linkage robot. The first injection molding machine produces the first product. The robot takes the product out and puts it into the second injection molding machine to produce the second one. In principle, it is the same as the manual pick-and-place product, but the efficiency. It will be much higher, the dimensional accuracy will be more stable, and it will not require the inventory of semi-finished products. Linked robots have unique advantages in the sanitary industry, especially the processing of showers. The labor input is reduced by about 60% compared with traditional manufacturing, but it needs The two machines are matched for production, and the flexibility of production is not high.
Combined with LSR application
The liquid silicone rubber LSR is suitable for high-demand applications. Because of its excellent electrical insulation, heat resistance, cold resistance and light resistance, it is harmless to the human body, so it is very useful in various fields such as medical treatment and electronics. Wide range of applications, currently in the field of two-color injection molding, LSR and plastic are also used in two-color processing to meet various needs.
Liquid silicone has a very wide hardness range, which can replace TPU, TPE and other thermoplastic elastomers, and can produce very good tactile texture. At the same time, liquid silicon also meets the requirements of many extreme environments. The material of liquid silicon has become an emerging popular choice in various industries, and it has gradually entered everyone's daily life.
Sandwich injection
Sandwich injection molding, also known as sandwich injection molding or surface-core processing technology, can completely inject a material into the surface material. It can be used for refill filling, hardness and toughness blending, and different requirements for product center of gravity adjustment. Improve the performance requirements of the product and ensure the appearance of the surface.
An internationally renowned sanitary ware company introduced sandwich injection molding and optimized in the addition of secondary materials, which can save 35% of raw materials in one year. At the same time, it can make rational use of the secondary materials that could not be added, which greatly enhances the manufacturing of the enterprise. Competitive in terms of cost.
Cube mold
The cube mold can fully utilize the time of mold opening for cooling, thereby greatly improving the production efficiency and increasing the capacity of the equipment to the limit.
It has a very prominent advantage in the production of thin-walled and large-volume products. The only drawback is that the mold input cost is extremely high, and the equipment needs to be customized.
In the current multi-color molding process, the advantages of the cube mold in terms of efficiency are unparalleled. This process fully utilizes the opening and closing mode in the molding cycle, and the ejecting time has outstanding advantages in mass production.
Multi-color injection molding process requirements
Soft and hard plastic two-color design:
The two materials must have a certain temperature difference in the melting point. Generally, it is recommended to reach 60°. It is recommended to be at least 30°. The melting temperature of the first shot material is high. Generally, the first shot is PC or PC/ABS, and the second shot is TPU or TPE, PC thickness is 0.6-0.7mm, soft rubber part thickness is required to be 0.4mm or more.
Try to widen the contact area, make the groove to increase the adhesion, or use the core for the first shot, and the second part of the material is injected into the first shot. The surface of the first shot is rough as much as possible.
Material compatibility
Multi-color injection molding mating materials must meet two basic compatibility conditions, which are compatible with the bonding compatibility and processing.
Transparent and non-transparent bijective design
‧ Double-lens design of small lenses
The first shot is non-transparent, the second shot is made of lens, the first shot uses PC to have a high melting point, and the second shot uses PMMA.
‧ Transparent and non-transparent bijective design for decoration
The first shot is a non-transparent material, the second shot is a transparent material, the non-transparent material is commonly used for SABIC PC material temperature, the second shot transparent material PMMA or PC. PC needs to be sprayed with UV to protect, PMMA can choose uv or strengthen If the surface has characters, you must choose UV.
Two-color injection mold features
The moving mold is the same. The injection molding process is rotating and needs to be exchanged, so the moving mold must be exactly the same. (There are special cases, the cavity can be different when molding)
After the injection molding of the first shot of the mold is completed, it cannot be left on the mold, preferably a hot runner, otherwise it can be grasped by a robot, and the worst is a latent gate, which can be automatically detached. Otherwise, the gate remains on the mold. The second shot is not consistently produced.
The product is shot twice. After the product is opened, the first shot must be left on the movable mold side. Generally speaking, it is generally chosen to leave both products on the movable mold side, so the mold needs a shutter. , pull rods, etc. to achieve sequential mold opening, first open the fixed mold side, on the fixed mold side need to add the ejection mechanism.
Process evaluation for multicolor injection molding:
Two-color injection molding is a very mature molding process. In the initial stage of mold development, analogy analysis can be performed by various CAE software. The analog operation of the model can accurately determine the mold and various parameters of the molding.
Materials Analysis
The analysis of materials is a key issue in the development of two-color injection molding. With the increasing market demand, a variety of materials are appearing in the field of two-color injection molding, and reasonable material selection during the development phase has become a very The key link. The more rigorous approach is to use the CAE software for surface compatibility and binding simulation test, data selection.
Waterway analysis
In the mold development stage, the waterway is a crucial link, because if the cooling is insufficient or unstable during the two-color injection molding process, it will cause defects in the appearance of the product, so the distribution of the waterway must be done seriously during the development stage. Review.
Analysis in areas such as LSR
In LSR and other emerging molding processes in China, we can also analyze some software to determine the possible problems in the molding process, and thus reduce the non-performing rate of the production process.
In summary, the multi-color injection molding technology has developed over the years, and its forming branches have become more and more perfect. It can be applied to various fields well, and the manufacturing efficiency is extremely high, which can satisfy the different practical requirements. Therefore, it is gradually being widely used, and it has good economic benefits in the automotive industry, electronics, medical fields, etc. It is a technology with great development potential. In these branches, sandwich injection molding, cube mold, LSR molding because of its own In terms of environmental protection, high efficiency, and excellent application performance, these products have distinct advantages. These processes have gradually become a hot trend in the industry, and slowly enter everyone's daily life. We also hope that multi-color molding process can be used for everyone. The production brings more exciting.