Due to the different uses of consumer products, different materials are used in different parts to meet the needs of specific environments and achieve the purpose of prolonging product life, increasing aesthetics and practicability. This practical design requirement will undoubtedly complicate the production technology, and the two-color
injection molding process is born in response to this trend. Below, Shanghai Mulan
The two-color injection molding factory will share with you the principle of two-color injection molding and the basic requirements of the process.
Two-color injection molding refers to the molding method of injecting two different colored plastics into the same mold. It can make the plastic parts appear in two different colors, and can make the plastic parts present regular patterns or irregular moiré patterns, so as to improve the practicability and aesthetics of the plastic parts.
The pairing materials of two-color injection molding must meet two basic compatibility conditions, namely, bonding compatibility and two-color injection molding process compatibility.
1. Transparent and non-transparent bijective designs
Two-shot design for small lenses: the first shot is made of non-transparent, the second shot is used as a lens, the first shot uses PC with a high melting point as much as possible, and the second shot uses PMMA. Transparent and non-transparent double-shot design for decoration: the first shot is a non-transparent material, the second shot is a transparent material, the non-transparent material is commonly used PC with high material temperature, and the second shot is a transparent material.
2 shot transparent material with PMMA or PC. PC needs to be sprayed with UV for protection, PMMA can choose UV or reinforcement, if there are characters on the surface, UV must be selected.
2. Two-shot design of soft and hard glue
There must be a certain temperature difference between the melting points of the two materials. Generally, it is recommended to be 60°C, and it is recommended to be at least 30°C. The melting point 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 to 0.7mm, software 0.4mm or more. Try to widen the contact area, make grooves, etc. to increase the adhesion, or the first
The first shot adopts core pulling, the second shot part of the material is injected into the first shot, and the surface of the first shot mold is as rough as possible.
3. Mold requirements
Two-color mold: Two plastic materials are injected on the same injection molding machine and molded twice, but the product is only molded once. Generally, this molding process is also called double-material injection molding, which is usually completed by a set of molds and requires a special two-color injection molding machine. It generally has the following requirements:
①The two shapes of the female mold must be different, forming a product respectively, while the two shapes of the male mold must be exactly the same;
② After the front and rear molds of the two-color injection mold are rotated 180°, they must match;
③ The total thickness of the front formwork panel plus A-plate cannot be less than 170mm. It is necessary to carefully check the thickness of the mold, the distance of the KO hole, etc.;
④ The nozzle of the three-plate mold can be designed to be able to automatically remove the mold;
⑤When designing the master mold for the second injection, in order to prevent the second master mold from scratching the glue position of the product that has been formed in the first time, a part of the void can be designed. However, the strength of each sealing position must be carefully considered. In injection molding, whether there will be plastic deformation under high injection pressure, resulting in the possibility of a batch front in the second injection molding;
⑥During injection molding, the product size of the first two-color injection molding can be slightly larger, so that it can be pressed more tightly with another male mold during the second molding, so as to achieve the effect of sealing
⑦Pay attention to whether the flow of plastic will impel the product that has been formed in the first time during the second injection molding, causing its glue position to deform;
⑧Before the A and B boards are closed, pay attention to whether the front mold slider or the inclined top will reset first and crush the product;
⑨The arrangement of the water transportation of the two female molds and the male mold should be as sufficient and balanced as possible;
⑩99% of the cases are the hard rubber part of the two-color injection molding product first, and then the soft rubber part of the injection molded product, because the soft rubber is easy to deform.
The principle and process requirements of two-color injection molding. Shanghai Mulan Two-color Injection Molding Factory said that two plastic materials are injected on the same injection molding machine and molded in two parts, but the product is only molded once. Generally, this molding process is also called double-material injection molding, which is usually completed by a set of molds and requires a special two-color injection molding machine. The two plastic materials are not necessarily injected on the same injection molding machine, and they are molded twice; after the product is taken out of one set of molds, it is put into another set of molds for the second step.
Two-shot two-color injection molding. Therefore, in general, this molding process is usually completed by 2 sets of molds, without the need for a special two-color injection molding machine.
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