The two most important processes for two-color plastic co-extrusion are filling and pressure holding. How to control the pressure in the two-color injection molding process is our years of accumulation of extrusion technology.
1. Two-color plastic co-extrusion pressure: In the current two-color co-extrusion process, the co-extrusion pressure of almost all extrusion machines is based on the pressure exerted by the plunger or the top of the screw on the plastic. The role of extrusion pressure in co-extrusion is to overcome the flow resistance of the plastic from the barrel to the cavity, give the molten material the rate of filling the mold, and compact the molten material.
2. Two-color plastic co-extrusion plasticizing pressure: In co-extrusion, the plasticizing pressure needs to be changed with the screw design, product quality requirements, and different types of plastics. If these conditions and the screw speed are the same, increase The plasticizing pressure will strengthen the shearing effect, that is, it will increase the temperature of the melt, but it will reduce the plasticizing efficiency, increase the countercurrent and leakage current, and increase the driving power.
In addition, increasing the plasticizing pressure can make the melting temperature uniform, the mixing of the pigments, and the discharge of the gas in the melt. In general operation, the decision of plasticizing pressure should be as low as possible under the premise of ensuring good product quality. The specific value varies with the types of plastic two-color molds used, but usually rarely exceeds 20 kg/cm².