Introduction: Two-color injection molding is a classic molding process. It uses two materials to injection mold into one product, which can achieve different appearance effects of color and touch.
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Today we will introduce and review in detail the five major sections: What is two-color injection molding? What are the advantages of two-color injection molding? Working principle of two-color injection molding . Material, process and mold requirements for two-color injection molding . Main applications.
Double-shot molding is a process where two different colored plastics are melted in two barrels, then injected through the same nozzle at the same time or one after the other. You can use two injection molding machines or a two-color injection molding machine to make products with different mixed color patterns, or products with clear color separation.
After the energy-saving transformation of the injection molding machine, the system can respond quickly, the injection molding machine can quickly adjust the supply according to its own needs, and the utilization rate of the injection molding machine’s electrical energy can be effectively improved to achieve high efficiency and energy saving.
Fast response is one of the important signs of the dynamic quality of the servo system. Since the production transition process time is short, generally within 200ms, to meet the overshoot requirements, the front edge of the transition process is required to be steeper, and the rise after energy-saving transformation is larger. The time it takes for the injection molding machine to reach rpm is less than 0.03 seconds.
The system uses double closed-loop control of pressure and flow to determine how much the injection molding machine needs. When you change something or something changes outside, the system can get back to normal pretty quickly.
Accuracy is how well the output follows the input. The servo motor uses permanent magnet technology, which is accurate and fast. The servo motor uses PLC technology, which is even more accurate. The error is usually between 0.01~0.00LMM.
Get a fast response, repeat the same thing over and over again, and keep the speed the same; use two different materials or two different colors at the same time, which saves a lot of time and money; it’s really easy to set up and change the settings.
Two-color injection molding products require a male mold and two female molds. The first injection molding is in the male mold and the first female mold. After molding, open the mold and directly switch to the second female mold without demolding. After the second injection molding, the two-color injection molded product can be obtained after demolding.
a. The front mold has two different shapes and forms two products, while the rear mold has the same shape.
b. The nozzle of the three-plate mold is designed to automatically release the mold, which makes the work more convenient. Pay attention to whether the demolding action of the soft glue nozzle is reliable.
c. The front and rear molds of the mold are rotated 180 degrees from the center. When rotating, the front and back must be consistent. This inspection must be carried out during work as it requires high positioning of the formwork. The total thickness of the front formwork plus plate A should not be less than 170 mm. This should be done by carefully checking the injection molding machine model and other reference data.
d. When designing the second injection molding master, in order to prevent the secondary master from scratching the glue position of the first molded product, a component can be designed to avoid voids. However, the strength of each sealant must be carefully considered, that is, whether the plastic will deform under large injection pressure during injection molding, which may lead to the possibility of a second injection molding front.
e. When doing injection molding, the first molded part can be a little bigger because it can be tightly pressed with another male mold in the second molding to achieve the sealing function. And pay attention to the second injection. Does the plastic flow affect the first molded part? Is the plastic position deformed? If possible, we must find ways to improve.
f. Before clamping plates A and B, pay attention to whether the front mold slider or inclined top will reset first and crush the product. So we had to find a way to have the A and B plates clamped first, then the front module slider. Or tilt the top to reset. The water delivery arrangement of the two front and rear molds is as adequate as possible, and the balance is the same.
This type needs two front molds and one back mold. The product is finished in one shot. It doesn’t need to be taken out of the beer machine in the middle. The product looks good and beautiful. The material thickness of the second injection molding is generally 0.5-2MM. The cost is higher and is generally used for comparison. Small product.
This type needs two front molds and two rear molds. After the first injection molding, the semi-finished product must be taken out and put into the second mold for the second injection molding. The product appearance is not very good. The requirements for injection molding technology are high. Generally, the second injection molding material can be up to 3MM to make larger products.
Two-color injection molding technology uses two different materials for injection molding, so the selection of two different materials is also an important process. Generally, two plastics with different colors are used, which can greatly improve the strength and durability of the injection molded product. It also makes it easier to fuse and shape.
However, products with special uses may need to take advantage of the situation where the properties of two materials are very different, which requires solving the problem of difficulty in fusion of two materials with large differences.
The main problems are delamination and shedding, which are fatal blows to injection molded products. Therefore, careful consideration is needed for the shrinkage rate and different interface conditions, and the proportion of materials must be adjusted.
For two-shot molding, the two materials must meet two basic compatibility conditions: adhesion compatibility and processing compatibility.
In addition, the following requirements must be met: injection unit, parallel and same direction, parallel and opposite, horizontal and vertical L-shaped, Y-shaped single-cylinder injection structures; mixing nozzle, patterns, waves, flow marks, gradients, interlayers, etc. Special nozzle;
Clamping mold, standard type, vertical turntable type, horizontal turntable type, rotating shaft type, robot rotating type and other mechanisms; feeding, in addition to standard hydraulic motor drive, there is also ESD (ElectricScrewDrive) electric feeding structure; oil circuit, there is ACC pressure accumulation High-speed injection and closed-loop design.
In double-shot design of soft and hard glue, the two materials must have a certain temperature difference in their melting points. It is generally recommended to be 60°C, and it is recommended to be at least 30°C. The melting point temperature of the first shot material is high. Generally, the first shot is PC or PC/ABS, and the second shot is generally PC or PC/ABS. The second shot is TPU or TPE, PC is 0.6-0.7mm thick, software is 0.4mm or more.
Try to widen the contact area as much as possible, make grooves, etc. to increase the adhesive force, or use core pulling for the first shot, and inject part of the material of the second shot into the first shot, and make the surface of the first shot mold as rough as possible.
Transparent and non-transparent double-shot design. Double-shot design of small lenses: the first shot is opaque, and the second shot is made of lenses. The first shot should be made of PC with a high melting point, and the second shot should be PMMA. Transparent and non-transparent double-shot design for decoration: the first shot is opaque material, the second shot is transparent.
The two female molds must be different to form two different products, while the two male molds must be the same; the front and rear molds of the mold must be consistent after being rotated 180° from the center; the maximum capacity needs to be carefully checked. Mold thickness, minimum mold thickness, KO hole distance, etc.; the nozzle of the three-plate mold is best designed to allow automatic demolding action.
when designing the master mold for the second injection molding, in order to avoid the second master mold scratching the first The glue position of the formed product can be partially designed to avoid voids. However, the strength of each sealing position must be carefully considered; during injection molding, the size of the first injection molded product can be slightly larger so that it can be pressed more tightly with the other male mold during the second molding to achieve sealing. The function of glue.
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Be careful that the flow of plastic doesn’t hit the part that was made the first time during the second shot, causing the glue line to deform; before you close the mold with plates A and B, make sure that the front mold slide or the angle pin doesn’t hit the part first and damage it when it resets; try to get the water flow in the two cavities and the core as even and balanced as possible; in 99% of the cases, you shoot the hard rubber part of the part first and then you shoot the soft rubber part of the part because the soft rubber part is easy to deform.
The structure of two-color injection molded products is very different from ordinary plastic products. Because two different materials are used for injection molding, the products have two different properties and characteristics, which are fundamentally different from ordinary injection molded products; at the same time, before injection molding, careful structural design of two-color injection molded products is required, and the compatibility characteristics of the two materials should be fully considered.
Two-color injection molding technology uses two different materials for injection molding, so the selection of two different materials is also an important process. Generally, two plastics with different colors are used, which can greatly improve the strength and durability of the injection molded product. It also makes it easier to fuse and shape. However, products with special uses may need to use two materials with extremely different properties.
This is a difficult problem to solve, because the two materials are relatively different. The main problems are delamination and shedding, which are fatal to injection molded products. Therefore, we must carefully consider the shrinkage rate and different interface conditions, and adjust the proportion of materials.
When designing the structure and shape of the product, we must first consider the purpose and use of the product, and conduct detailed research on the size and internal structure. Generally, we need to increase the contact area of the two raw materials to enhance the firmness.
Here, we can design many small grooves and convex grooves inside the product for inlaying and stitching. This can increase the contact area of the two materials, so that when we perform injection molding, we can better improve the strength and service life of the product and enhance its practicality.
This kind of mold requires different considerations in the molding part. First, the concave and convex grooves of the two injection molds need to be carefully designed to ensure a tight fit during docking. At the same time, when designing the demoulding mechanism, a second injection is required before demoulding can be carried out.
Different injection molding methods need to be differentiated in different details. After the vertical rotation injection machine is demoulded, the product is ejected to complete the relevant operations. However, if the demoulding situation cannot be ejected by the injection machine, a hydraulic device must be used for demoulding mold.
The two-color injection molding machine can complete the injection molding of two colors or materials in one injection molding process, avoiding multiple injection molding and assembly steps, and improving production efficiency.
Save the cost of melting and printing, increase the beautiful visual effect of the product, and improve the grade and added value of the product. Compared with traditional single-color injection molding technology, the two-color injection molding machine can reduce manual operations and production links, reduce production costs and labor costs.
The two-color injection molding machine is equipped with a dedicated mold and control system, which can achieve high-precision color positioning and alignment, ensuring the consistency and beauty of the product appearance.
Not only has the function of anti-slip and increasing friction, the flexible resin material makes it more ergonomic and feels very good. The two-color injection molding technology brings more possibilities to product design, and can create more colorful and unique appearance effects to meet the personalized needs of consumers.
Two-color molds can combine two resins and colors with different characteristics into a single two-color product, which can decrease the assembly and post-processing tasks of molded products. Additionally, two-color injection molding technology can decrease errors caused by multiple assembly, thus decreasing scrap and improving product quality and consistency.
Two-color injection molded products have high quality stability, easy control of product deformation, short molding cycle and high output value. The loss can be 7% lower than that of rubber-coated injection molding, and the product manufacturing cost can be 20%-30% lower than that of rubber-coated injection molding.
Used in power switches, mobile buttons, car switches, etc., to meet certain light guide or light transmission requirements.
Used in handheld products, such as walkie-talkie shells, toothbrush handles, power tool handles, wrenches and thermos cups, etc., to improve the feel.
Used in products with multiple color appearance requirements, such as keyboards, using two-color injection molding, which is beautiful and does not worry about being rubbed off during use.
Used in products that require waterproofing to achieve waterproofing requirements.
The two-color injection molding process has now been widely used in almost all plastic fields such as automobiles, electronic products, power tools, medical products, home appliances, toys, etc.
Used in products that require local electroplating, such as feature buttons, etc.
In the plastic family, only ABS and polysulfone (PSU) surfaces can be electroplated. If a local area or one side of the product requires electroplating, the electroplated area must be injected with ABS, and the area that does not require electroplating must be injected with other materials such as PC. etc.
In summary, two-color injection molding technology has been around for a long time, but it has only been recognized and used in recent years because the products made with it are adaptable to the environment in which they are used.
At the same time, it can be molded in one step, which saves money, allows for precise positioning, encourages design innovation, reduces waste, and ensures that the quality of the products is stable. It can meet different requirements, so it is being used more and more widely and has a big impact on the automotive industry and other industries. It has good economic benefits and is a technology with a lot of potential.
Injection molding is a widely used manufacturing process for producing plastic parts. Two-color injection molding is a variation of this process that enables the creation of parts with two or more colors or materials in a single operation. This article will cover the basics of two-color injection molding and its advantages and limitations.
Two-color injection molding is a process that combines two different materials or colors to produce a single part. The process involves using a two-shot injection molding machine, which has two separate injection units. The first injection unit injects the first material into a mold cavity, while the second injection unit injects the second material on top of the first material.
The mold cavity for two-color injection molding has two or more cavities that are designed to produce different sections of the part. The two-shot machine rotates the mold, allowing the second material to be injected into the second cavity, producing a two-color or two-material part in a single molding operation.
Two-color injection molding offers several advantages over traditional injection molding. Here are some of them:
Despite its many advantages, two-color injection molding has some limitations that manufacturers should be aware of. Here are some of them: