Two-color injection molding refers to a molding process in which two different materials are injected into same set of molds, so as to realize injection molded parts made of two materials.
A complete two-color or even multi-color injection molding program requires integration of injection molding machines, molds, turntables, automation, and auxiliary equipment. Complex structure and non-standard customization of two-color multi-color injection molding machine are much higher than that of single-color injection molding machine.
In recent years, with development of industrial technology, multi-color (multi-component) injection molding technology has been widely adopted.
Technical development of two-color machine can be divided into two main technical orientations. One is represented by European and American companies, which is biased towards versatility. It is based on single-color injection molding machine plus related configurations to form a two-color machine. Its characteristics are: Dual-purpose machine.
Second is that Japanese and Taiwanese companies are represented, and they are more specific. Its two-color machine is a special model, and integrates many customized functions, which is more suitable for professional mass production of two-color products.
Among many injection molding machine companies in the Greater China region, one of them is dedicated two-color machine of FCS. Precision two-color machines developed by FCS include turntable, rotary shaft, electric, sandwich, and color mixing machines.

 

FB-200R The first generation of two-color machine dedicated to pen making-2003
Since 2000, two-color machine technology has undergone four major developments: large-scale, precision/specialization, multi-injection and multi-function, and vertical axis of rotation.

Before 2006, domestically produced large-scale two-color machines were extremely rare in Chinese market. With increasing market demand for medium and large two-color machines, industries including automobiles, home appliances, notebook computers, and large-scale daily necessities have begun to adopt two-color technology in large quantities, two-color machines have begun to develop toward large-scale development.
For example, since 2006, FCS introduced large two-color machines with a clamping force of 700 tons or more into Ningbo plant to realize localized mass production of medium and large two-color machines, and set a milestone in the development of large two-color machines in Chinese market.

Precision development of two-color machine is mainly reflected in use of a hybrid two-color machine. Oil-electric injection molding machine has a lower cost than full motor, but it can effectively improve energy consumption and poor accuracy of traditional oil pressure, greatly reduce pollution and noise problems.
In addition to precision of injection unit, continuous optimization and refinement of rotating structure is also an important development of two-color machine. Whether it is a turntable or a rotating shaft, from the earliest rack and pinion structure, to hydraulic motor drive, to servo electric drive, rotation speed and accuracy have been greatly improved.
Two-color machine is industry-specific and has a high degree of customization. Since 2000, two-color injection molding has been used in mobile phone industry, auto parts industry, electronic appliances, cosmetics and medical applications and other industries, showing a professional development trend.

 

Development of multi-component injection molding machines started with two-color machines. With increase in product complexity, demand for three-color or even four-color has begun to emerge.
From a technical point of view, accuracy requirement of multi-tasking turntable control is higher than that of two-station, so production cost of machine is relatively high, so there is no need to blindly pursue a multi-color machine with multiple tasks, but to choose the most efficient solution according to product structure requirements.
In terms of multi-functional development, what really enables multi-component injection molding machines with diverse functions and flexible production modes is realization of movable function of injection unit.
For example, "right-angle sky-side four-color machine" (LV type), combined with injection movement function, can realize single color, P type two color, L type two color, V type two color, L type three color, V type three color, LV type Eight functions including three-color type and four-color LV type.

 

Three-color taillights
For companies that tend to diversify their products, multi-function machines are an excellent choice. Take automotive lighting industry as an example. Through configuration of injection unit, a multi-color machine can meet production of automotive headlights and taillights at the same time.

At K exhibition in 2004, many horizontally rotating multi-color molds appeared, including: small horizontally rotating overlapping molds, horizontally rotating four-sided cube molds, and two-group horizontally rotating four-sided cube molds.
Among them, Milacron exhibited a 250-ton through-beam two-color machine, equipped with two sets of horizontally rotating twin cube turning stack moulds, combined four technologies of "two-color + IML (in-mold labeling) + IMA (in-mold combination) + rotating stack mould".
At 2007 K exhibition, KraussMaffei exhibited a 2,300-ton two-platen machine equipped with a horizontal rotating superimposed mold to produce automobile door trims.

 

KraussMaffei's 2300-ton two-platen machine is equipped with a horizontal rotating overlap die
It can be seen from above observations that after 2000, use of horizontal rotating molds in multi-color machines has expanded from a small 250-ton machine to a large-scale 2,300-ton machine.

Observed from previous K exhibitions in Germany, a combination of multiple applications appeared in multi-component molding technology.
For example: two-color + IML (in-mold labeling), two-color + IMA (in-mold assembly), two-color + overlapping mold, two-color + rotating overlapping mold + IMA, two-color + IML + IMA + overlapping mold, two-color + sandwich, two-color + Mucell (micro foaming) , three-color + IMA, etc.
However, high-tech products such as ultra-large horizontal turntable counter-injection machines, all-electric two-color machines, three-station three-color rotary machines, and four-color machines also appeared at this time.
In other words, multi-component molding technology must be combined with other technologies to create higher benefits and become a goal that must be challenged in the next stage.
Key issue is development of multi-component mold technology and automated peripherals. Whether it is in-mold labeling, in-mold assembly, horizontally rotating four-sided overlapping molds, micro-foaming, silicone molding, etc., related molds and peripheral cooperation are required.
Therefore, technical integration and joint development of injection molding machines, molds, and automation peripherals are key to development of multi-component molding technology. Only in this way can a highly automated production unit be formed.
In the future, two-plate horizontal turntable multi-color machine will continue to deepen its development, especially application of horizontally rotating four-sided overlapping molds. Combined with electric drive units, such as rotating units, injection molding units, etc., is also an important foundation for multi-color machines to achieve high precision and multi-function.
With advancement of intelligent injection molding machine technology, application of technology such as multi-cavity flow balance, injection melt variation control, and online mold clamping force monitoring has enabled multi-component injection molding machines to gradually develop in the field of high-efficiency.
China has the largest automotive market and the largest injection molding machine business. It is expected that two-color injection molding will have greater achievements in the era of Industry 4.0, and era of intelligent automobile driving.