Injection molding is typically used to make plastic parts. If the pressure at the gate is monitored as a function of time during the injection of a thermoplastic polymer, identify the profile that best describes this event.
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In injection molding, always expect a pressure curve with three parts: sharp rise (filling), plateau (holding), and fall (cooling/solidification).
In the injection molding process of thermoplastics, the pressure profile at the gate is crucial for understanding how the material flows into the mold. During the injection cycle, the pressure initially increases as the molten polymer is injected into the cavity—this is followed by a pressure plateau and then a decrease once the cavity is filled, leading to the holding/packing phase. Here's a breakdown of the expected pressure profile features:
Initial Rise: The pressure climbs rapidly as the polymer is injected at high velocity to fill the cavity quickly.
Plateau phase: A leveled pressure indicating the cavity is filled and pressure is applied to pack the material to ensure a complete filling and compensates for material shrinkage.
Drop after filling: As the polymer cools and solidifies, the pressure decreases since the mold cavity is completely filled and material flow stops.
Given these characteristics, profile P best matches the expected pressure change during the injection molding of a thermoplastic polymer.
