Final answer:
Screw injection molding is a manufacturing process that involves injecting molten material into a mold. Thermoplastic and thermosetting plastics have different temperature requirements for the exit of the barrel and the die.
Step-by-step explanation:
Screw injection molding is a manufacturing process used to produce parts by injecting molten material, such as thermoplastic or thermosetting polymers, into a mold using a screw mechanism. The simplified sketch of screw injection molding includes a barrel, a screw, and a die. The relative temperatures at the exit of the barrel and in the die vary depending on the type of plastic. For a thermoplastic, the temperature at the exit of the barrel would be high to keep the material in a molten state, while the temperature in the die would be slightly lower to allow the material to solidify. On the other hand, for a thermosetting plastic, the temperature at the exit of the barrel would be lower to prevent the material from curing prematurely, and the temperature in the die would be higher to facilitate the curing process.
A sketch of screw injection molding involves a hopper, heated barrel with a screw, and a simple die. Thermoplastics exit the barrel at a high temperature and solidify in the cooler die, whereas thermosets soften at a lower temperature in the barrel and cure at a higher temperature within the die.
The sketch of screw injection molding would show a hopper where the raw material is loaded, proceeding to a heated barrel with a rotating screw. At the end of the barrel, the molten polymer is injected into a simple die that shapes the material into the desired part. Typically, the temperatures in the barrel for a thermoplastic material would be high enough to melt but below the degradation point, and it would cool after being injected into the die to harden into the final shape. On the other hand, for a thermosetting plastic, the initial temperature would be lower, since it only needs to soften enough for shaping. The material undergoes a chemical reaction within the die to harden permanently after injection.
For thermoplastics, the exit temperature of the barrel is high, allowing the material to flow into the die, and the die temperature is lower to solidify the part. For thermosets, the barrel temperature is just enough to soften and mix the polymer, while the die temperature is higher to initiate the cross-linking reaction and cure the part.