Plastic net tells the principle and process requirements of two-color injection molding

Two-color injection molding refers to a molding method in which two different color plastics are injected into the same mold. It can make the plastic parts appear in two different colors, and can make the plastic parts have a regular pattern or irregular cloud-like color to improve the practicality and aesthetics of the plastic parts.

Second, the principle of two-color injection

Double color mixing injection molding

It has two barrels, each of which is constructed and used in the same way as a conventional injection molded barrel. Each cylinder has its own passage communicating with the nozzle, and the opening and closing valves 2, 4 are also installed in the nozzle passage. During molding, after the melt is plasticized in the cylinder, the order of the melt entering the nozzle and the proportion of the discharged material are controlled by the opening and closing valves 2, 4, and then injected into the cavity by the nozzle. You can get a variety of plastic products with different color mixing effects.

Double pattern injection molding principle

It also has two barrels 1 and 5, the nozzle structure of which is somewhat special, in addition to the function of the usual nozzle, it can also be rotated by the gear 3 mounted at the rear. During molding, the different sizes of the melt are respectively plasticized in the cylinders 1, 5, and the gear 3 drives the rotary shaft 4 to rotate, so that the different colors of the melt alternately enter the cavity, thereby obtaining different colors in the form of radiation from the center to the periphery. Patterned plastic products.

Third, the requirements of two-color injection molding

Material requirements

Paired materials for two-color injection molding must meet two basic compatibility conditions, namely, adhesive compatibility and process compatibility.

Process requirements

Soft and hard plastic double shot design

There must be a certain temperature difference between the two materials. It is generally recommended to be 60 ° C. It is recommended to be at least 30 ° C. 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 0.6-0.7mm, software 0.4mm or more. Try to widen the contact area, make grooves 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 as rough as possible.

Transparent and non-transparent bijective design

The dual-lens design of the small lens: the first shot is non-transparent, the second shot is made of lens, the first shot uses the PC melting point as high as possible, and the second shot uses PMMA.

Transparent and non-transparent two-shot design for decoration: the first shot is a non-transparent material, the second shot is a transparent material, the non-transparent material is usually a PC with a high temperature, and the second transparent material is a PMMA or a PC. The PC needs to be sprayed with UV to protect it. PMMA can be UV or reinforced. If there are characters on the surface, UV must be selected.

Mold requirements

Two-color mold: Two kinds of plastic materials are injection-molded on the same injection molding machine, and molded in two parts, but the product only molds once. Generally, this molding process is also called double-material injection molding, usually completed by a set of molds, and requires a special two-color injection molding machine. It generally has the following requirements:

1. The two shapes of the master must be different, forming one product separately, and the two shapes of the male mold are exactly the same;

2. After the front and back molds of the mold are rotated 180° from the center, they must be matched;

3. The total thickness of the front mold panel plus the A board should not be less than 170mm. Need to carefully check the maximum die thickness, minimum die thickness, KO hole distance, etc.;

4. The nozzle of the three-plate mold can be designed to automatically release the mold;

5. When designing the second injection molding master mold, in order to avoid the second master mold scratching the first molded product glue position, you can design a part to avoid the air. However, the strength of each sealant position must be carefully considered (ie, in the injection molding, will the plastic be deformed under large injection pressure, which may result in the possibility of a second front injection?);

6. When molding, the size of the first injection molding product can be slightly larger, so that it can be pressed tighter with another male mold in the second molding to achieve the function of sealing.

7. Note that in the second injection molding, whether the flow of plastic will impinge on the first molded product, so that the glue position is deformed;

8. Before the A and B plates are closed, it is necessary to pay attention to whether the front die slider or the inclined top will first reset and crush the product;

9. The water transport arrangement of the two female and male models is as full as possible and balanced;

10, 99% of the situation is the first hard plastic part of the injection molding product, and then the soft rubber part of the injection molding product, because the soft rubber is easy to deform.