2 shot injection molding (double shot mold), as its name suggests, is a part of two plastic injection molding. Generalized 2 shot injection molding includes overmolding, which is realized by ordinary injection molding machine and two injection moldings. Narrow 2 shot injection molding refers to injection molding of two different plastics on the same machine by a two-color injection molding machine.
The former does not require high equipment, but production efficiency is low. It is basically only suitable for forming materials that are not highly soft and hard. The latter’s scope of application, product quality and high production efficiency are current trends.
First, 2 shot injection molding requirements
Paired materials for double shot mold must meet two basic compatibility conditions, and bond compatibility and processing are compatible. And also it must meet following requirements:
(1) Injection unit, parallel co-directional, parallel-oriented, horizontal and vertical L-type, Y-type co-directional single-cylinder injection structure;
(2) Mixing nozzles, special nozzles such as patterns, waves, flow marks, gradients, and interlayers;
(3) Clamping, standard, vertical rotary, horizontal rotary, rotary, robot rotary and other institutions;
(4) Feeding, in addition to standard hydraulic motor drive, there is ESD (ElectricScrewDrive) electric feeding structure;
(5) Oil circuit, with ACC accumulator high-speed injection and closed circuit design.
Second, 2 shot injection molding characteristics
High performance and high energy consumption: After energy-saving transformation of injection molding machine, system can respond quickly. Injection molding machine can quickly adjust supply according to its own needs, which can effectively improve utilization rate of injection molding machine, thus achieving high efficiency and energy saving.
Good stability: System is double closed loop control of pressure and flow, and supply of injection molding machine is determined according to requirements of injection molding machine. System can reach a new equilibrium state after a short adjustment process or return to original equilibrium state under given input or external disturbance.
Fast response: Rapid response is one of the important indicators of dynamic quality of servo system. Due to short production process time, generally within 200ms, in order to achieve overshoot requirements, frontier of transition process is required to be steep, and rate of increase after energy saving is improved. To be large, injection molding machine reaches 1500 rpm for less than 0.03 seconds.
High precision: Accuracy after transformation refers to accuracy with which output can follow input. Servo motor adopts permanent magnet technology, which is accurate and rapid. Servo motor adopts PLC technology, and control is more precise. Allowable deviation is generally between 0.01 and 0.00lmm.
Energy saving: Adopting a blanking system to reduce power consumption.
Improve efficiency and reduce cost: Achieve high response, high repeatability, and improve speed stability; use two kinds of raw materials or two colors to form at the same time, greatly reducing process and manpower to achieve cost savings; parameter setting, system adjustment to Very simple digital operation.
Third, 2 shot injection molding features
Double shot mold: Two kinds of plastic materials are injection-molded on same injection molding machine, and molded in two parts, but product only molds once. Generally, this molding process is also called 2 shot injection molding, usually completed by a set of molds, and requires a special two-color injection molding machine. Double shot mold are becoming more and more popular on the market today. In this process, appearance of product can be more beautiful, and it is easy to change colors without spraying, but cost is high and the technical requirements are high.
*Two shapes of master mold are different, and one product is formed separately, and two shapes of male mold are exactly the same.
*Front and back molds must be aligned after being rotated 180 degrees from center. This inspection must be done during design, which requires high positioning of mold base.
* Total thickness of front mold panel plus A board should not be less than 170mm. Please review other reference data for this type of injection molding machine, such as maximum die thickness, minimum die thickness, KO hole distance, etc.
* Nozzle of three-plate mold can be designed to automatically release mold. Pay special attention to whether demolding action of soft glue nozzle can be smooth.
* When designing second injection molding master, in order to avoid second master mold inserting (or rubbing) first molded product glue position, you can design a part to avoid air. However, strength of each sealant must be carefully considered. That is, in the mold manufacturing, will plastic be deformed under the large injection pressure, which may result in possibility of second shot?
* When mold manufacturing, size of 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 function of sealing.
* Note that in the second shot mould, will flow of plastics impulsively melt plasticized position of first molded product? If this is possible, we must find a way to improve it.
* Before A and B plates are clamped, pay attention to whether front mold slider or inclined top will first reset and crush product? Therefore, it is necessary to find a way to first clamp A and B plates, then slider of front die or slanted top can be reset.
* Water distribution of two master and male models is as full as possible, equal and same.
*99% of cases are hard rubber part of injection molding product first, and then soft rubber part of injection molding product. Because soft rubber is easy to deform.
