The mold-shaping method is to first mold the mold, then add the rubber to the cavity, pressurize and inject the rubber at the same time. After filling the glue, the mold is moved to the flat vulcanizer for vulcanization. The compression molding method is to first fill the rubber (or pre-formed semi-finished product), and then press mold and vulcanize.
The difference between the die-casting method and the molding method is that the mold is injected after the mold is closed. The glue injection method is to load the rubber into the cylinder under a specific press, and press the rubber into the cavity through a high pressure of 50 to 80 MPa. After filling the glue, the mold is transferred to a vulcanizing machine for vulcanization. This method is between the molding method and the vulcanization by injection molding. It is easy to fill the rubber and the product is even and dense. It is suitable for the manufacture of products with complex structure and large volume. The disadvantage is that the blank requires a long time to produce and the production efficiency is low.
The mold for the die-casting method also has a runner system, which is the same as the injection mold and the injection mold. However, when the shift mode mold is in operation, the pressure injection nozzle of the mobile injector is aligned with the gate, and the rubber is forcibly injected into the cavity of the mold by strong pressure.
The die casting method requires that the rubber used should be soft, low in hardness, and easy to plasticize and flow. In order for the compound to be quickly injected into the mold cavity, its plasticity and fluidity must be improved. For this reason, polyethylene, zinc stearate, wax, soap and lubricating oil lubricants should be added to the formulation of the compound to minimize the Mooney viscosity.
Due to the high injection speed, the mass fraction of the accelerator in the rubber is 10%~20% less than that of the general rubber to prevent the rubber from scorching in the gate area. In addition, when the rubber compound is used, it is not suitable to apply talc powder, stearic acid and liquid separator containing clay, but an appropriate amount of slip-moisting agent can be added to the rubber cylinder of the injector to improve the fluidity of the rubber compound.