What is Two-Color Injection Molding?

2023-12-27



Table of Contents

1. Introduction

2. What is two-color injection molding?
3. What are the advantages of two-color injection molding?
4. How two-color injection molding works?
5. Two-color injection molding requirements for materials, processes and molds
6. Application of two-color injection molding
7. Conclusion




1. Introduction


Two-color injection molding technology, as an important technology in the field of plastics processing, has been widely used in the modern manufacturing industry. It enhances the added value of products by using two different plastic materials in a single injection molding process, which endows products with unique aesthetics and practicality. This blog will introduce in detail the principle, process characteristics, application areas, etc. of two-color injection molding technology to deepen the understanding of the technology.





2. What is two-color injection molding?


Two-color injection molding refers to the use of two different colors of plastic raw materials in a single injection process, through a specific injection molding machine and injection mold, the two plastics at the same time or separately injected into the cavity of the injection mold, after cooling and curing to obtain the plastic products with two colors.



The difference between overmolding and two-color injection molding should be explained here:


Overmolding is to make a plastic part of one color on the first single color injection molding machine, and then manually put this plastic part into the second mold for plastic injection molding, without the need for a special injection molding machine. Two-color injection molding is done by a two-color injection molding machine, there are also two injections, but all of them are done inside the two-color injection molding machine, usually using a special two-color injection molding machine.






3. What are the advantages of two-color injection molding?


Reduced assembly steps: Traditional plastics processing requires multiple steps and component assembly, while two-color injection molding can complete the entire product in a single injection process, reducing the number of assembly steps and increasing production efficiency.


Diversified design: two-color injection molding can produce plastic products with two or more colors or materials, so that the products have a richer and more personalized appearance and touch, to meet the consumer's demand for product aesthetics and practicality.


Reduced production costs: Two-color injection molding reduces material waste and scrap rates during the production process, as well as reduces assembly steps and labor costs, thus lowering overall production costs.


Improve product quality and stability: Two-color injection molding can produce plastic products with high precision and consistency, which improves product quality and stability and reduces product defects and performance fluctuations.


Can be used for complex product design: two-color injection molding is suitable for the production of plastic products with complex structure and difficult design, such as parts with multiple colors or material changes, multi-curved surfaces or shaped products.


Environmental Sustainability: Two-color injection molding reduces waste and pollutants in the production process, while optimizing the use of materials and reducing energy consumption, in line with the requirements of environmental sustainability.


Customizable production: two-color injection molding can be customized according to customer needs, providing more personalized product solutions to meet the needs of customers for specific products to meet.


Good abrasion resistance and anti-skidding: Two-color injection molding products have good abrasion resistance and anti-skidding, which can improve the service life and reliability of the products and are suitable for products that need to be used frequently or exposed to harsh environments.




4. How two-color injection molding works


The molding of two-color injection molded products requires a male mold and two female molds, the first injection in the male mold and the first female mold, after molding, open the mold, without demolding, directly switch to the second female mold for the second injection, demolding can be obtained after the finished product of two-color injection molding. In actual production, two groups of male molds are usually used, each group is responsible for one injection, and the different female molds are switched by rotating 180° vertically.





5. Requirements for materials, processes and molds for two-color injection molding



1) Requirements for materials


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



2) Process requirements


Hard and soft rubber double shot design


The two materials must have a certain temperature difference between the melting point, generally recommended for 60 ℃, it is recommended that at least 30 ℃ or more, the melting temperature of the first shot material is high, generally the first shot is PC or PC / ABS, the second shot is TPU or TPE, PC thick 0.6-0.7mm, software 0.4mm or more.


Try to widen the contact area, do grooves and so on to increase the adhesion, or the first shot using the core, the second shot part of the material injection molded into the first shot inside, the first shot mold surface as rough as possible.



Transparent and non-transparent double-shot design


Double-shot design for small lenses: first shot for non-transparent, second shot for lenses, try to use PC with high melting point for the first shot, PMMA for the second shot.


Decorative transparent and non-transparent double-shot design: the first shot for non-transparent materials, the second shot for transparent materials, non-transparent materials commonly used for high material temperature PC, the second shot of transparent materials with PMMA or PC. PC need to be sprayed with UV to protect the PMMA can be selected for UV or reinforced, such as the surface of the characters must be selected for UV.



3)Requirements for injection molds


1. The two shapes of the female mold must be different, molding a product separately, while the two shapes of the male mold should be exactly the same.


2. The front and rear molds of the die must coincide after rotating 180° from the center.


3. The maximum mold thickness, minimum mold thickness, KO hole distance, etc. need to be carefully checked.


4. The spout of the three-platen mold should preferably be designed for automatic demolding action.


5. In the design of the second injection of the mother mold, in order to avoid the second mother mold to avoid the first has been molded products rubbing the glue bit, can be designed part of the avoidance of empty. But must carefully consider the strength of each sealing bit.


6. When injection molding, the size of the first injection molded product can be slightly larger so that it can be pressed more tightly against another male mold during the second molding to seal the glue.


7. Pay attention to the second injection molding, the flow of plastic will not impulse the first already molded products, so that its glue position deformation.


8. Before the A and B plates are molded together, pay attention to whether the front mold slider or tilt top will reset first and crush the product.


9. Arrangement of water transport for both female and male molds is as adequate and balanced as possible.;


10. 99% of the cases are first injection molded products of the hard plastic part, and then injection molded products of the soft plastic part, because the soft plastic easy to deformation.





6. Application of two-color injection molding


The two-color injection molding process is now widely used in automobiles, electronic products, power tools, medical products, home appliances, toys and so on in almost all plastic fields.


Showcase the two-color process products from several areas.






7. Conclusion


Overall, two-color injection molding is a powerful and flexible plastics processing technology that offers many advantages to manufacturers, including improved product quality, lower production costs, increased productivity and more design freedom. As technology advances and consumer needs continue to change, we can expect two-color injection molding to play an even more important role in the future.