Two component injection molding
DATE：2020/12/22 8:45:11 / READ： / SOURCE：This station
Two component injection molding
In recent years, a series of new injection molding processes have been introduced, such as two-component (multi-component) injection molding, injection blow molding, injection pull blow molding.
Bicomponent injection molding includes two-color, two-component and double-layer composite injection molding, and the equipment structure is roughly the same.
1. Two color injection molding
Two kinds of plastics of the same kind with different colors are plasticized by two barrel and then injected into the same nozzle at the same time or successively. A control valve is installed between the material sheet and the nozzle, which acts with the plasticizing screw (or plunger) at the same time and is controlled by the program. Another type is that the nozzle is equipped with a rotating mandrel to produce a radial pattern. The product is mixed color, with a variety of patterns. Two parallel or relatively set injection devices share a mold locking system. The mold can be rotated 180 ° to obtain color mixing products with obvious color separation.
2. dual component foam molding
First, the material without foaming agent (surface material) is injected into the mold cavity, and then the core material containing foaming agent is injected into the mold cavity by the same nozzle. At the same time, the surface material is extruded and compacted to the cavity wall. At this time, the mold cavity is full. Due to the cooling shrinkage, a small amount of material without foaming agent is injected into the mold cavity to close the gate, so as to obtain the surface without shrinkage and collapse Products.
(1) Equipment features: the injection molding equipment is basically the same as the ordinary injection molding machine, but two sets of plasticizing and injection molding devices are required. The nozzle used has a special structure and locking nozzle to ensure that the two components can be completely separated when passing through the nozzle.
(2) Process characteristics: ① the material should be dried in advance and then added with foaming agent; ② the injection temperature of the core layer is related to the foaming agent. When exothermic foaming agent is used, the barrel temperature should be 10-20c lower than that of the ordinary injection molding; ③ the mold temperature should not be too low to avoid the surface material freezing quickly, which is not conducive to the core material polishing. Generally, ABS is 5-i5c, and the modified PPO is 80-90c; (4) the amount of material used in the surface and core layer depends on the use requirements (strength, etc.), the shape and size of the products, the molding process conditions, etc., usually taking the core material that can be completely coated as the criterion: (5) the injection speed is related to the factors such as injection molding and mold structure, etc., usually with slower injection speed to ensure the laminar flow of the melt, so that the products with good surface quality are: the cooling time of the two-component foam plastics. It is related to the wall thickness, dimensional accuracy, mold temperature and the amount of foaming agent. In order to avoid free spraying, the sprue of the mold should be set to ensure that the two components are evenly filled. The vent hole can be vented through the gap of the parting surface. The diameter of the cone near the product of the central gate should be greater than the wall thickness of the gate to avoid free spraying. If the sub gate or film gate is used, it should be greater than 2mm.
(3) It has the following characteristics: 1) the core material is completely covered by the surface material; 2) it is light in weight and has good sound insulation and shock proof effect; 3) it can form large-scale products with a general thickness of 8-10 mm, good bending strength and rigidity; ④ (8) it can be used to reduce the thickness of the core material, and (5) it can be used to process the surface of the waste product, such as the thickness of the core material can be reduced.
Author：admin