What is the difference between plastic die casting and compression molding? Please be specific
In recent years, press molding has been applied to thermosetting blends such as urea formaldehyde plastics, phenolic resins, epoxy resins, melamine resins, and rubber. Although some materials are available for injection molding, compression molding is still very common. Die casting material is more flexible than plastic material. Many thermosetting materials with high impact (1.0ft lb) and good notched impact strength retention, only in the limit under pressure will flow.
With the rapid development of the modified polymer materials, new improvements have been required in the compression molding industry. Two mold plastic molding reinforced (plug): male and female die (cavity). When the mold is filled with reinforcing material, the two molds of the mold are closed and then heated and pressurized to solidify the product. The complexity of the molds to be matched varies greatly. Aluminum, plastic or steel can be used.Lightweight materials are less expensive to make and are generally used in short-term production such as "cold molding"". Room temperature curing resins for cold moulding, but still use moulds and press presses. Long term production of hardened steel mold is more cost-effective, for cutting off the mouth can provide better shear performance and excellent finish. These plastic steel dies are mechanically adapted to cut through the mold and usually face the die block. The metal mold with this pair of dies has a uniform surface and a good finish. The closed die process is used in compression molding, die casting, injection molding and some stamping reinforced composites.
Equipment: simple, but also the main features of plastic equipment. The two halves of the platen are joined together to heat and pressurize the material into a predetermined shape. Most pressing processes are hydraulically operated; pneumatic operations are also used. On the two plate moves in the 4 corner posts up and down under pressure. According to the size of press and mould equipment, the pressure is usually 20 - 1000 tons. The size of the platen is usually 8 inches, 2 to 5 feet, 2.There are different degrees of automation in the mold release after charging and curing. The most modern hydraulic press is often used. Previous simple systems include temperature control, pressure control, stop pressure control, and time control. Modern equipment is controlled by more advanced microprocessors. For thinner products, a heating cylinder or belt heater can be used in the plate. For deeper parts, use a cylindrical electric heater, steam heating or hot oil heating system. There are several kinds of pressure heating system used in plastic with uniform temperature steam heating mode, but the heating temperature limit below 350 DEG F; barrel heating or other heating (heating coil, heating etc.) is relatively clean, easy to maintain, with more universal; oil heating, because the heating medium circulation is stable, so the uniform heating. Now there are many new heating methods, hot water heating, similar to hot oil heating, heating medium, one water, one gas combustion, continuous cycle, can provide higher plastic temperature.
The obvious advantage of plastic forming of thermosetting materials is the simplicity of the system. Place the material in a heated cavity and keep it to the desired time. Because the process is simple and the cost is low. Additives and reinforcing agents are irregular and have better strength. Since there is no gate and runner, no waste of materials, mold almost no maintenance. The parts have good uniformity, no casting and flowing marks, and reduce the cost of modification. According to the structure of the product and the application characteristics of the plastic, we can use full pressure mold, semi pressure mold and closed die (see the article about the plastic mould).
