Piezoelectric Cavity Core Adjustment for Micro Resonator Frequency Stabilization
Dynamic piezo core adjustments during moulding freeze sub-micron resonator dimensions, stabilizing frequency and eliminating post-moulding laser trim steps.
Bulk Modulus Relaxation
Meaning
Thermodynamic properties in polymer melts determine how pressure and volume interact during the solidification phase of injection moulding. The phenomenon of bulk modulus relaxation governs how the volumetric resistance of a compressed polymer melt decreases over time under a constant strain. This behavior is critical during the packing and holding phases where the material is subjected to high pressures that gradually decay as the polymer cools and undergoes phase transition.
Time Dependency
Compressibility in polymer systems is not an instantaneous elastic response but a time-sensitive process. During bulk modulus relaxation, the polymer chains slowly reorganize to accommodate the applied compressive load. This molecular rearrangement occurs over seconds, altering the effective bulk modulus of the polymer from its initial glass-like value to its long-term rubbery state.
Process Influence
Precision injection moulding requires accurate prediction of part shrinkage and warpage. When bulk modulus relaxation occurs too rapidly, the cavity pressure drops faster than expected, which leads to inadequate packing and localized sink marks. Process engineers adjust packing time to compensate for this transient behavior.
Viscoelastic Behavior
Viscoelastic properties dictate how melt pressure relates to cavity volume during cooling. Under steady temperature conditions, bulk modulus relaxation is directly linked to the free volume within the polymer matrix. As the temperature falls toward the glass transition point, the relaxation rate slows dramatically.