Melt Pressure Transducers for Injection Molding? Wait, what??
- Bob
- Mar 22
- 2 min read
A comparison of the two applications for Pressure Sensors with NoNonSensor Tech.
Melt transducers are used in both plastic extrusion and injection molding processes, but they serve slightly different roles due to the nature of these two processes. Here’s a breakdown of the key differences:
1. Purpose and Function:
• Plastic Extrusion Melt Transducer:
• In extrusion, the melt transducer measures the pressure or flow rate of the molten plastic as it is pushed through a die to form a continuous shape (like film, sheet, or tubing). The melt transducer ensures that the pressure is within the desired range for a consistent and uniform extrusion process.
• These transducers are primarily concerned with monitoring the melt flow and ensuring the pressure at the die is stable for an even extrusion process.
• Injection Molding Melt Transducer:
• In injection molding, the melt transducer typically measures the pressure of the molten plastic as it is injected into a mold cavity. This helps monitor the injection process, ensuring that the correct pressure is maintained during the filling of the mold and that the part is filled evenly and completely.
• The focus is on the pressure at the injection point, as the molten plastic is rapidly injected into the mold, where it will cool and solidify.
2. Pressure Range:
• Extrusion: The pressure in the extrusion process is generally more constant but lower, as the material is continuously pushed through the die.
• Injection Molding: The pressure in injection molding can be much higher because the material needs to be injected quickly into the mold cavity under high pressure to fill it accurately.
3. Flow Characteristics:
• Extrusion: In extrusion, the material flows continuously in a steady stream. The melt transducer monitors this steady-state flow, ensuring that the extrusion rate is consistent throughout the process.
• Injection Molding: The flow in injection molding is more dynamic, with a rapid injection phase followed by a packing phase. The melt transducer in injection molding often helps track these phases to ensure proper cavity filling and part quality.
4. Design and Sensitivity:
• Extrusion: The transducer used in extrusion is typically designed to handle the continuous, low-to-medium pressure flows, and may be optimized for longer-term, steady monitoring of melt pressure at the die.
• Injection Molding: Injection molding transducers are designed to handle higher peak pressures that occur during the short burst of injection. These sensors are often more sensitive to rapid pressure changes and may include features to compensate for the dynamic changes in pressure as the melt fills the mold.
5. Location in the System:
• Extrusion: The transducer is usually located near the die or extrusion nozzle, monitoring the pressure at the point where the material exits the extrusion barrel.
• Injection Molding: The transducer is located in the injection molding machine at the injection nozzle, directly measuring the pressure as the material is injected into the mold cavity.
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