As the name suggests it is an injection molding machine which can process 2 colors of plastic material at the same time. It normally has 2 injection units which processes one material at a time. These 2 material can be injected simultaneously or at different times based on the product requirement.

A tooth brush is a fine example for the parts manufactured using these machines.

1、 what is two color injection
The so-called two-color injection molding refers to the molding method of injecting two different colors of plastic into the same mold. It can make the plastic parts two different colors, and can make the plastic part of a regular pattern or irregular cloud pattern color, in order to improve the practicality and beauty of the plastic parts.

2、 Two color injection molding principle
Double mixed color injection molding

Two color injection diagram
It has two cylinders, and the structure and usage of each barrel are the same as those of ordinary injection molding. Each barrel has its own passages connected with the nozzles, and the opening and closing valves are 2 and 4 in the nozzle passageway. When molding, the molten material is plasticized in the barrel, and the opening and closing valves 2 and 4 control the order of the molten material into the nozzle and the proportion of the discharge material, then the nozzle is injected into the mold cavity. All kinds of plastic products with different mixing effects can be obtained.

3、Requirement of two color injection
Material requirements
Two color injection molding matching materials must meet two basic compatibility conditions, namely, adhesion compatibility and processing compatibility.

technological requirements

Double fire design of soft and hard glue

The two materials must have a certain temperature difference, generally recommended at 60 degrees centigrade, suggested at least 30 degrees centigrade, the melting point temperature of the first material is high, the first one is PC or PC/ABS, second is TPU or TPE, PC thick 0.6-0.7mm, and software 0.4mm above.
As far as possible to widen the contact area, do grooves and so on to increase adhesion, or the first shot to use the core, second injection part of the material injection into the first inside, the first surface of the die as rough as possible.

Transparent and non transparent bifire design

Small lens dual-beam design: the first shot to do non-transparent, the second shot to do lenses, the first shot as high as possible with PC melting point, the second shot with PMMA.
The transparent and non transparent double fire design for decoration is first shot as non transparent material, second as transparent material, non transparent material is commonly used as PC with high temperature, and second for transparent material using PMMA or PC. PC needs to be sprayed with UV to protect. PMMA can choose UV or reinforcement. If there are characters on the surface, UV must be selected.

Mould requirements
Two-color mold: two kinds of plastic materials in the same injection molding machine, two molding, but the product only mold once. Generally, this molding process is also called double injection molding, usually by a set of molds, and a special two-color injection molding machine is needed.

In general, there are the following requirements:
1, the two shapes of the female die must be different, forming a product separately, while the two shapes of the male die must be exactly the same.
2, after the center of the mould is rotated by 180 degrees, the mold must be identical.
3. The total thickness of the front panel plus A board should not be less than 170mm. The maximum thickness of the mold, the minimum thickness of the die, and the distance of the KO hole should be carefully investigated.
4, the water outlet of the three plate die can be designed to be automatically demoulding.
5. In the design of the master mold for the second injection molding, in order to avoid the second master mold scratching the first molded product glue level, you can design a part of the avoidance of void. But it is necessary to carefully consider the strength of each sealing site (i.e., in the injection molding, is there a plastic deformation under the large injection pressure, resulting in the possibility of a batch front in the second injection molding). ;
6, injection molding, the first injection molding product size can be slightly larger in order to make it in the second time the molding can be more tight with the other, in order to meet the sealing effect;
7. Pay attention to the second injection molding, plastic flow will impulse the first has been formed products, so that the glue deformation;
8, before A or B plate clamping, it is necessary to pay attention to whether the front mold slider or inclined roof will first reset and crush the product.
9, two mother mold and public mode of water distribution as far as possible, and balanced;
10, 99% of the situation is first injection of hard rubber part of the product, and then injection molding products soft rubber part, because the soft rubber is easy to deform.