In the die casting process, the thermosetting resin material is added to a separate material cavity, often called a material tank, and then forced into one or more closed molds for polymerization (curing).
The sprue also called the sprue and runner, which allows the material to flow from the trough to the cavity, and pass through the restrictor or gate before entering the cavity. Many cavities have a single trough. The air in the material cavity is replaced by the incoming material and discharged through a specially placed exhaust port.
When the material is placed in the trough, the material is measured in a compact measuring device, and then preheated to close to the polymerization temperature. Add enough injection volume at a time.
The force of the preheated raw material out of the trough sends it to an injector, which is mounted on the trough immediately to prevent leakage from the gap between the piston and the edge of the trough. The sealing sleeve is usually clipped into the injector to further prevent leakage.
The surface maintenance of chute, injector, gate, runner, and mold cavity can make the raw material solidify quickly. The temperature is 280-380°F according to the material properties, mold design, and part geometry.
When the die casting is near the curing period, demold the complete die casting, including removing the gate, runner, sprue, and trough to form a solidified mat (residual material).
In die casting, preheating of the material is very important. The cold material flows slowly, and the material that enters the cavity first has not reached its endpoint, that is, it may polymerize. If the above situation occurs, the product quality is poor, not only in appearance but also in mechanical properties. There are some exceptions, such as a small injection volume or some low viscosity materials. It can be heated by a heating lamp or a furnace, but an effective and commonly used method is to use a dielectric heater specially made for plastic molding.
Screw-type plasticizing and heating of thermosetting materials are also commonly used now. This equipment can be combined with the molding equipment, or it can be independent, with the advantages of reducing the volume and measuring the feed amount accurately, and must be combined with the pre-forming in other systems.
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