Two-Color/Multi-Color Injection Molding Technology And Material Selection

Two-color injection molding means that a part is realized by injection molding of two kinds of plastics.

Two-color injection molding in a broad sense includes overmolding, which is realized by two injection molding by ordinary injection molding machines.

In a narrow sense, two-color injection molding refers to the use of a two-color injection molding machine to inject two different plastics into the same machine to complete the parts, and the common one is rotary.

The former does not require high equipment, but the production efficiency is low, and it is basically only suitable for the molding of two materials that do not require a high degree of soft and hard rubber. The latter has a good scope of application, good product quality, and high production efficiency.

Two-color injection molding requirements

The paired materials for two-color injection molding must meet two basic compatibility conditions, adhesive compatibility and processing compatibility. In addition, the following requirements must be met:

(1) Injection unit, parallel, parallel, opposite, horizontal and vertical L-shaped and Y-shaped single-cylinder injection structures;

(2) Mixed nozzles, special nozzles such as patterns, waves, flow marks, gradients, interlayers, etc.;

(3) Clamping die, standard type, vertical turntable type, horizontal turntable type, shaft type, manipulator rotation type and other mechanisms;

(4) For feeding, in addition to the standard hydraulic motor drive, there is also an ESD (ElectricScrewDrive) electric feeding structure;

(5) The oil circuit has ACC accumulating high-speed injection and closed-circuit design.

Two-color injection molding characteristics

High performance and high energy saving: After the energy saving transformation of the injection molding machine, the system can respond quickly, and the injection molding machine can quickly adjust the supply according to its own needs, which can effectively improve the utilization rate of the electric energy of the injection molding machine, so as to achieve high efficiency and energy saving.

Good stability: The system is double closed-loop control of pressure and flow, and the supply of the injection molding machine is determined according to the demand of the injection molding machine. Under the action of a given input or external disturbance, the system can reach a new equilibrium state after a short adjustment process, or return to the original equilibrium state.

Good fast response: Fast response is one of the important signs of the dynamic quality of the servo system. Due to the short production transition time, generally within 200ms, in order to achieve the requirements of overshoot, the frontier of the transition process is required to be steep, and the rising rate after the energy saving transformation is required. To be large, the injection molding machine takes less than 0.03 seconds to reach 1500 rpm.

High precision: The precision after transformation refers to the degree of accuracy that the output quantity can follow the input quantity. The servo motor adopts permanent magnet technology, which is accurate and fast. The servo motor adopts PLC technology, and the control is more precise. The allowable deviation is generally between 0.01 and 0.00lmm.

Energy saving: The billet taking system is adopted to reduce power consumption.

Improve efficiency and reduce costs: achieve high response, high repeatability, and improve speed stability; using 2 kinds of raw materials or 2 kinds of colors can be molded at the same time, greatly reducing the process and labor to achieve cost savings; parameter setting, the system is adjusted to Very simple digital manipulation.

Two-color mold selection

1. Wear resistance. When the blank is plastically deformed in the mold cavity, it flows and slides along the surface of the cavity, causing severe friction between the surface of the cavity and the blank, resulting in the failure of the two-color mold due to wear. Therefore, the wear resistance of the two-color mold material is one of the most basic and important properties of the mold. Hardness is the main factor affecting wear resistance. In general, the higher the hardness of the two-color mold parts, the smaller the amount of wear and the better the wear resistance. In addition, wear resistance is also related to the type, quantity, shape, size and distribution of carbides in the material.

2. Strong toughness. Most of the working conditions of the two-color mold are very bad, and some often bear a large impact load, which leads to brittle fracture. In order to prevent the sudden brittleness of the two-color mold parts during operation, the two-color mold must have high strength and toughness. The toughness of the two-color mold mainly depends on the carbon content, grain size and organizational state of the material.

3. Fatigue fracture performance. During the working process of the two-color mold, fatigue fracture is often caused under the long-term action of cyclic stress. Its forms include small-energy multiple impact fatigue fracture, tensile fatigue fracture, contact fatigue fracture and bending fatigue fracture. The fatigue fracture performance of the two-color mold mainly depends on its strength, toughness, hardness, and the content of inclusions in the material.

4. High temperature performance. When the working temperature of the two-color mold is high, the hardness and strength will decrease, resulting in early wear of the mold or plastic deformation and failure. Therefore, the two-color mold material should have high anti-tempering stability to ensure that the two-color mold has high hardness and strength at working temperature.

5. Heat and cold fatigue resistance. Some two-color molds are in a state of repeated heating and cooling during the working process, which causes the surface of the cavity to be subjected to tension, pressure and stress, causing surface cracking and peeling, increasing friction, hindering plastic deformation, and reducing dimensional accuracy. Causes the failure of the two-color mold. Hot and cold fatigue is one of the main forms of failure of hot work dies, and these dies should have high resistance to cold and heat fatigue.

6. Corrosion resistance. When some two-color molds such as plastic molds are working, due to the presence of chlorine, fluorine and other elements in the plastic, strong corrosive gases such as HCI and HF are decomposed after heating, which erodes the surface of the two-color mold cavity, increases its surface roughness, and aggravates wear. invalid. Therefore, materials with superior corrosion resistance must be selected in the processing of two-color molds.