Laminating die is also called laminating die. There are two ways of die non rotation and die rotation. There are two kinds of rotary die technology: rotary die technology and die technology with built-in rotary mechanism. Its characteristic is that two components can be injected at the same time, which greatly shortens the production cycle of the product. In addition, the use of hot runner laminated injection mold can give full play to the ability of injection molding machine, save manpower and equipment resources, and greatly improve production efficiency.
It has the following characteristics:
1. Different from the conventional mold, the cavity of the laminated injection mold is distributed on two or more layers and arranged in an overlapping manner, that is to say, multiple pairs of molds are stacked and combined together. The most common two-layer lamination die is usually installed by two single-layer die back-to-back, and the parting surface usually depends on the gear and rack mechanism to keep synchronous opening.
2. Generally, when the injection molding machine is used with the conventional mold, its injection volume and opening stroke are only 20% ~ 40% of the rated value, which does not give full play to the performance of the injection molding machine. Compared with the conventional die, the production efficiency of the two-layer laminated die is nearly 100% higher than that of the standard die, and the die locking pressure is only about 10% higher than that of the standard die. It greatly improves the equipment utilization and productivity, and reduces the injection cost.
3. The laminated injection mold is most suitable for forming large flat parts, shallow cavity shell parts, small multi cavity thin-wall parts and parts that need mass production.
Double layer lamination technology can also produce two different products at the same time, for example, the first layer mold produces one product, while the second layer mold produces another product, which can be a combination of the same or different materials, the same or different colors, etc. For example, the cover of the first layer of injection container and the main body of the second layer of injection container can be realized by using the laminated mold.
Key design points of two-layer hot runner injection mold
Maximum injection volume of injection molding machine
The material in the hot runner plate and the central main nozzle of the laminated hot runner injection mold does not affect the injection quantity required by the mold, which can be ignored. The injection volume of the injection molding machine is nearly twice that of the standard mold.
Injection pressure of injection molding machine
The verification of injection pressure is mainly to check whether the injection pressure can meet the needs of molding. Because of the hot runner technology, the injection pressure of the laminated hot runner die is larger than that of the single-layer cold runner die due to the increase of the process and projection area. When checking the injection pressure, the injection pressure of the plastic parts should be determined according to the injection process of various plastics, combined with the computer simulation flow analysis, and then compared with the rated injection pressure of the injection molding machine.
Maximum clamping force of injection molding machine
Each layer cavity of the laminated injection mold is set "back to back", and the theoretical locking force does not increase. However, the projection area of the plastic part plus the gating system on the parting surface is increased due to the increase of the flow channel of the central main nozzle and the splitter plate of the laminated injection mold; Moreover, the flow channel is extended due to lamination, the pressure loss is larger than that of the conventional single-layer mold, and the injection pressure increases correspondingly, resulting in the increase of the cavity pressure, so the clamping force is increased. It is safer to increase the clamping force by 10% ~ 15% according to the same single-layer mold during verification.
Opening stroke of injection molding machine
The laminated injection mold divides the mold and the ejection parts at two levels. When checking the opening stroke, the simultaneous interpreting mechanism with the same transmission ratio should be adopted, such as the rack and pinion or the connecting rod die opening device. The opening stroke is 2 times that of the single mold.
Length of main nozzle
The center main nozzle should not be too long or too short, so that when the mold is closed, the center main nozzle will not exceed the maximum distance of the injection molding machine nozzle in the base backward or forward. Since the central main nozzle and the middle part of the mold are to move together during parting, it is necessary to ensure that the central main nozzle remains in the fixed mold after opening, so as to prevent the overflow at the head of the central main nozzle from dropping into the cavity wall of the fixed mold.
gating system
The hot runner pouring system of the laminated injection mold can transfer the injection pressure well, improve the molding quality of the plastic parts, and realize the automatic production easily, but it has certain requirements for the plastic varieties, and the hot runner system is expensive.
Mold temperature control system
Mold temperature is one of the important factors affecting the molding quality of plastic parts. In the design of laminated injection mold, the temperature condition of each layer cavity should be controlled consistently. For the laminated hot runner injection mold, in order to reduce the heat loss of the hot runner system due to heat conduction, the contact area between the mold and the hot runner plate should be reduced, and the corresponding heat insulation pad should be set.
Die opening mechanism
In order to make the shrinkage of plastic parts consistent, the residence time (cooling time) of plastic parts in each mold cavity should be equal, so the laminated injection mold should ensure that the parting surface of each mold cavity is opened at the same time. Rack and pinion drive mechanism and mechanical linkage mechanism are often used as the opening mechanism of laminated injection mold. The former has better technical performance and economy, but the latter has more flexibility.
Demoulding mechanism
According to the requirement of equal cooling time, the laminated injection mold shall eject the plastic parts in each layer cavity at the same time.
It is composed of a double material injection molding machine, a set of two-layer mold and an intermediate template which can rotate 180 ° repeatedly. After the first injection of the injection molding machine, the mold will be opened after cooling, and the middle mold will rotate 180 ° according to the design requirements, turning the first injection molded part attached to the mold core to the second mold cavity, and then closing the mold for injection.
