Multi-color Multi-material Injection Molding Process

Mold Design

In principle, there are two types of mold designs for multi-color and multi material injection molding. First, the mold has more than two rubber inflow channels, and the primary molded product is moved to another mold cavity through a rotating device (turntable or rotating bearing mechanism) or moving mechanism (manual hand, robot or hydraulic sliding mechanism). After the mold is closed, the concept of the mold here for over-injection molding is that you must consider how to transfer the part from one cavity to another. Second, the mold shares a runner system that injects two or more materials into the cavity of the traditional mold. This multicomponent injection molding method is often called Sanwichmolding or co-injection. Chuck injection molding now has two methods: double-cylinder injection molding and single-cylinder injection molding. The following is a brief description of several common multi-color and multi-material designs.

Turntable

After the first molding is opened, the turntable rotates 180 degrees, and the first molded product matches the mold cavity of the second molding. After the mold is closed, the second molding is performed. All injection molding units in this process can be injected simultaneously.

In addition to the 180-degree forward and reverse rotation of the turntable, due to special product production requirements, the turntable is designed to rotate on multiple sides, which can produce or inlay injection molding of three materials or more. The drive of the turntable can be hydraulic or servo driven, but whether the manufacturing technology of the turntable is good or not directly affects the quality and efficiency of forming.

The turntable method is often used to produce products with surface sizing.

Centering Rotation

The mold has a rotating central axis. The rotating central axis can be rotated by a rack or a hydraulic motor. After the first molding mold is opened, the core connected to the central axis is ejected by the ejection system of the injection molding machine, and is lifted together with the workpiece from the lower mold. The rotating mechanism then Rotate the workpiece 180 degrees to form the second cavity. All injection molding units in this process can be injected simultaneously. In addition to the 180-degree forward and reverse rotation of the trolley, due to special product production requirements, the trolley can also be designed to rotate on multiple sides to produce injection molding of three or more materials (such as in-mold assembly, etc.).

Core Back Technology (Core Back)

In primary molding, after waiting for the product to cool to a certain hardness, the mold part retreats and sinks from the core to form a secondary cavity with the same shape as the core, and then performs secondary molding.

The advantage of this method is that there is no need to open or move the initial molded product during the molding process, and the number of mold cavities will double on an injection molding aircraft of the same tonnage; the disadvantage is that the two materials must be injected strictly in sequence. The cooling cycle is long and the entire injection molding cycle is long. In addition, the requirements for the second injection molding have also become higher. If the adjustment molding is not mastered well, chuck failure and retracted cloak may occur.

This process is only suitable for secondary forming of regular shapes.

Use Robot or Human Hands to Move and Drop

After the mold is opened for primary molding, the finished product is taken out by robot or manually and transferred to the secondary cavity of the same mold. After the mold is closed, secondary molding is performed. All injection molding units in this process can be injected simultaneously.

The advantage of this method is that the mold cost is low and the two parts of the core cavity can be completely independent. Therefore, the process advantage over the molding combined with silicone rubber LSR is obvious. Access by robots and human hands requires precise positioning.

This process is only suitable for products with simple structure.

Neutron Slide

After the mold is opened for the first molding, the core is pushed down to the opposite side by the hydraulic system, and matches the second mold cavity for the second molding.

Synchronous Injection Molding

After the mold is closed, the two materials are injected into the same mold cavity at the same time. This process may result in uneven weld lines between the two materials and is only suitable for products with lower appearance requirements.

Rotating Laminated Type

Rotating laminated mold technology uses a horizontal turntable placed at the bottom of the injection molding machine. The first molding mold is rotated horizontally by 90 degrees or 180 degrees through the driving of the horizontal turntable. After the mold is closed, secondary molding is performed on the parting surface of the other mold. . This is a laminated multi-material type combination. Since the mold closing projected areas of the two molding molds overlap, the production capacity may be doubled if the mold clamping force of the machine is sufficient, but the molds and equipment are expensive.

Chuck Injection Molding Technology

The two injection molding units of the injection molding machine are for injecting outer material and sandwich material. The initial injection station first injects the outer material into the mold cavity. After reaching the predetermined measurement, the second injection station fills the middle layer material into the outer plastic, fills the entire mold cavity, and forms a product with different materials for the inner and outer layers.

The above-mentioned multi-color and multi-material injection molding processes provide an effective method for the "multi-color" design and manufacturing of products. Choosing the appropriate process is crucial to the success of the project. With the development of technology, more and more innovative possibilities are provided for the design and production of multi-color plastic products. Choosing the appropriate multi-color, multi-material injection molding technology must comprehensively consider factors such as product design, materials, injection molding equipment, mold design, as well as automation and investment plans. Each technology has advantages and limitations, and suitability for practical application is most important.