What are the temperature requirements for plastic injection molding?
The setting of plastic injection molding temperature is considered the "lifeline" of injection molding process control. Its accuracy directly affects the dimensional stability, mechanical strength, and surface finish of the product.
Generally, the processing temperature needs to find a balance between the material's melting temperature (Tm) and decomposition temperature (Td). Taking common ABS as an example, its melting temperature is approximately 105℃, and its decomposition temperature is above 250℃. Therefore, the barrel temperature should be set between 210-240℃, requiring precise control like walking a tightrope.
Different plastic materials have significantly different temperature requirements: crystalline materials such as PP (polypropylene) need to exceed their distinct melting point (160-170℃), and the barrel temperature often uses a gradient increase from the rear to the front, typically 180-230℃; while non-crystalline materials such as PS (polystyrene) can be flexibly adjusted within a wider range (180-280℃), like a symphony conductor adjusting the "temperature symphony" based on the product thickness.
The injection mold temperature is also crucial. High-gloss products require a temperature of 80-100℃ to eliminate weld lines, while ordinary parts can be satisfied with 40-60℃.
Temperature control must consider material fluidity. Too low a temperature will lead to a sudden increase in melt viscosity, resulting in underfilling or ripple defects; while too high a temperature may cause material degradation, producing bubbles or burn marks. Temperature parameters can be fine-tuned by observing the injection pressure and product appearance.
Modern injection molding machines are equipped with PID intelligent temperature control systems, which can control temperature fluctuations within a reasonable range, providing a "constant temperature cradle" for precision injection molding.