1. Barrel Temperature: The melt temperature is of paramount importance; the barrel temperature settings used serve merely as a guideline. The actual melt temperature can be measured at the nozzle or determined using an air-shot method. The barrel temperature settings depend on the desired melt temperature, screw speed, back pressure, shot volume, and molding cycle time. If you lack experience processing a specific grade of plastic, please begin with the lowest recommended settings.
For ease of control, the barrel is divided into zones; however, these zones are not necessarily set to the same temperature. For long production runs or high-temperature operations, set the temperature of the first zone (the rear zone) to a lower value; this prevents the plastic from melting prematurely and bridging within the feed throat. Before commencing the molding process, ensure that the hydraulic oil, hopper dryer, mold, and barrel are all at their correct operating temperatures.
2. Melt Temperature: The melt temperature plays a primary role in determining the flow properties of the molten material. Since plastics do not possess a single, precise melting point-but rather a melting *range*-the influence of temperature on flowability varies depending on the structure and composition of the polymer's molecular chains. Rigid molecular chains (such as those found in PC and PPS) are significantly more sensitive to temperature fluctuations. Conversely, the flowability of flexible molecular chains (such as those in PA, PP, and PE) does not change as drastically with temperature adjustments. Therefore, appropriate injection temperatures must be selected and calibrated based on the specific material being processed.
3. Mold Temperature: Certain plastics require higher mold temperatures due to their high crystallization temperatures or slow crystallization rates. Other materials may require specific mold temperatures-either high or low-to ensure dimensional stability, minimize deformation, or facilitate easy ejection from the mold. For instance, PC typically requires a mold temperature of at least 60°C, whereas PPS may require temperatures exceeding 160°C to achieve superior surface finish and improved flow characteristics. Consequently, mold temperature plays an indispensable role in optimizing product appearance, minimizing deformation, ensuring dimensional accuracy, and facilitating the molding process.
4. Injection Pressure: Injection pressure represents the force required for the molten material to overcome flow resistance as it advances through the mold; it directly impacts critical product attributes such as dimensions, weight, and deformation. The required injection pressure varies depending on the specific plastic product being manufactured. For materials such as PA and PP, increasing the pressure can significantly enhance flowability. Furthermore, the magnitude of the injection pressure determines the product's density-and, by extension, its surface gloss. There is no single fixed value for injection pressure; rather, as the difficulty of filling the mold increases, the required injection pressure must be correspondingly increased.
