Immetech’s Thoughts on Double-color Injection Molding Technology Processes

Immetech’s Thoughts on Double-color Injection Molding Technology Processes

Double-color molding is the one available process for managing product molding with two different materials and colors, using simultaneous molding processes in the same injection machine to output a single unit. Double-color molding is now widely used for electronic parts, electric tools, medical parts, home appliances, toys and almost all areas of plastic products. Center-stack Rotary Double-shot is one hot double-color molding method seen in recent years, differing from common double-color rotary injection molding, especially in the automotive injection molding sector, for products such as two-color door panels, lights and so on. The development of double-color mold manufacture and molding process, double-color or multi-color injection machines and double-color material is advancing rapidly, with several advantages:

1. Simplification of the assembly and post-processing process, saving costs in melting and printing, while increasingartistry and raising the products’ level and added value.
2. With anti-slip and increased friction functions, flexible resin is more ergonomic and feels better.
3. Increased quality stability, with easier control of product deformation, and a high yield with short cycle time. Comparing with overmolding, there is 7% less loss and a 20%-30% lower product manufacturing cost can be achieved.

Double-color injection molding technology types

According to the structure of the double-color mold, classification can be divided into: core rotation, core back type, push plate rotation. The core rotary type can be divided into split-type and combined type; the so-called split-type means two molds installed at one injection machine for the double-color injection purpose, which is now more widely used. The combined type means double-color molding with only one mold.

Double-color injection molding process features

1. Configuration of double-color injection machine: considering the molding effect, it is necessary to equip with two matching plasticizer injection devices for the same injection machine, not only for process needs, but also for the transformation purpose. The specifications of these two injection devices need to have the same function, apart from the structure. During the injection molding process, material temperature, injection pressure and injection speed in the two sets of equipment need to be adjusted consistently, to ensure final molding parts performance are at the same level, and then proceed to related fusion and integration work. Please be aware to align the parameters if there is inconsistency between the two injection devices.
2. The structure differences between double-color injection molding components and normal injection molding components: due to the unique characteristics for double-color injection molding components, there are some obvious differences in machine mechanism settings compared with ordinary injection machines. First of all, double-color injection molding components use a higher melt temperature and need a high temperature to maintain the flow ability; Secondly, it needs larger injection pressure, not only because using two different plastic materials, but to press it for welding needs strong pressure for fusion, and is designed to overcome the huge resistance of melt material flowing through the mold, to ensure filling smoothly.
3. Double-color injection molding technology material parameters setting: double-color injection molding technology uses two different materials for plastic product production, so materials have to be considered carefully before injection molding. Not only must material quality standards be considered, but also attention paid to controlling temperature, pressure and related parameters during molding. Due the difference between double-color injection molding technology and general injection molding, where the material used in double-color injection molding technology requires higher melting temperature parameters to ensure material won’t solidify before filling completion, ensure that you use the injection device to control material pressure well, enabling it to reach every area of the mold, and achieve injection molding purpose.

Double-shot injection mold design features

Double-shot mold is becoming more and more popular in the market, but it needs higher requirements for mold design, mold building and injection molding.

1. Molding: double-color mold molding is almost the same as other ordinary injection molding. The difference is that the convex/core side of the injection mold in two positions should be considered to be the same, concave/cavity side should fit well with convex/core side. These kind of molding parts are small.
2. Releasing: The release system will be ineffective during the first shot since double-color molding part can only release after the second shot. For parallel turntable injection machines, the ejection system in injection machine can be used for part release. For vertical turntable injection machines, it’s necessary to set up hydraulic ejection in rotary table, due to the inability to use the ejection system in injection machine.
3. Gating system: since is double-color molding, there are the first shot gating system and second shot gating system, from 2 different injection devices.
4. Mold: since double-color molding methods are special and need to cooperate and coordinate with each other, so the guiding device size and precision of both molds should be consistent. For parallel turntable injection machine, mold shut height must be same and the center of both molds should be on same rotation radius, only with 180° difference. For vertical turntable injection machines, both molds should be on the same axis.

From multi-color molding and double shot molding characteristics and applications we can see there is a tendency to replace the traditional injection molding process. Innovation in molding technology not only increases the precision of molding process and provides technology for difficult processes, but also develops a whole new scope of molding. Innovative molding technology and equipments can handle more and more diversified, high quality, high value-added products in response to increased demand. See the process in action here:

Immetech Industrial have developed more than 50 sets of double-color molds and provided solutions for many famous automotive enterprises in the world, including Ford, Volvo, Saic and other customers. Now Immetech has united with Ninghai Longhua to invest substantially in opening the largest double-shot, three-color and center-stack rotary double-shot injection machine professional molding factory and manufacturer in South China：Dongguan Shuangyu Technology Co., Ltd., with a full set of double-shot, three-color and center-stack rotary double-shot injection machine professional mold development technology, alongside supporting equipment and mature technology to support and provide services for Bentley, Tesla, Mercedes, Porsche, BMW, Audi and other global automotive industry manufacturers.