Introduction to two-color injection molding

1.1 The concept of two-color injection molding

Bumper Mold two-color injection molding (2K molding or two shot mold) refers to the process of one injection molding

A process in which two plastics (or two plastics of different colors) are molded into one piece.

In this paper, the material injected for the first time is called the base material, and the material injected for the second time is called the covering material.

The most common form of two-color injection mold is that two identical moving molds correspond to two different fixed mold cavities.

After the base material is injected for the first time, the movable mold is opened first, and then the movable mold is rotated 180° by the rotatable structure of the injection machine, and then the mold is closed, and the raw material of different color or color is injected for the second time using a different raw material (covering material ).

After the second mold opening, the punches for the two injections are demoulded.

The first base material injection and the second cover material injection are carried out at the same time, requiring two injection nozzles on the injection machine to inject different colors or different base materials and cover materials respectively.

1.2 The difference between two-color injection molding and insert injection molding

Two-shot injection molding differs from insert molding (or overmolding) in that:

1) Use ordinary injection molding machine for insert injection molding. After the product is taken out of one set of molds, it is put into another set of molds for overmolding.

Therefore, insert injection molding is usually completed by 2 sets of molds, and does not require a special two-color injection molding machine.

Two-color injection molding is a one-time injection molding of two kinds of plastics on a two-color special injection molding machine.

The two plastics are injected into the same injection molding machine and molded twice, but the product is ejected only once. Therefore, two-color injection molding is usually completed by a set of molds, which requires a special two-color injection molding machine.

2) During the whole process of two-color injection molding, the plastic is in a molten state without cooling shrinkage, which means that there is an opportunity to form a strong chemical connection between the base material and the covering material, with high strength and at the same time reducing the risk of burrs.

3) Compared with insert injection molding, two-color injection molding does not require an insert insert process, and the molding cycle is shorter, with higher efficiency and higher quality.

Advantages and disadvantages of two-color injection molding

2.1 Advantages of two-color injection molding

1) Increase the flexibility of product design

Two-color injection molding can integrate multiple functions into one plastic part, such as soft surface, ergonomic design, two-color appearance, brand identity, function improvement, noise reduction, shock absorption, waterproof and anti-collision, etc., which can save design space and reduce spare parts. number of parts etc.

2) Reduce the number of items to reduce costs

Multifunctional plastic parts can be completed by one injection molding, reducing secondary processing.

3) Different plastics are chemically bonded into one body, with higher quality and better strength.

2.2 Disadvantages or limitations of Bumper Mold's two-color injection mold

1) The compatibility of the two plastics needs to be considered

Since different plastics have different chemical properties, their compatibility will directly affect the bonding strength and bonding effect of the bonding surface, and not all plastics have good compatibility.

2) Small difference in plastic shrinkage

If the difference is too large, it will affect the bonding strength of the bonding surface and may cause product warping.

3) The shape of the finished Motorcycle Kit Mold product should not be too complicated