Resonant Frequency Shift

Physical Measurement

Sensor systems embedded in the mold or within the plastic part track changes in dielectric properties during the cooling phase. The resonant frequency shift provides a measure of how the polymer is solidifying and contracting inside the mold cavity. As the resin transitions from a molten state to a solid crystalline structure, its dielectric constant decreases, which alters the frequency of an embedded sensor.

This measurement gives real-time feedback on the state of the material without destroying the part.

Moulding Variable

Variations in processing conditions such as injection pressure or melt temperature alter the final density of the molded thermoplastic. This density variation causes a measurable resonant frequency shift when the finished component is analyzed with RF sensors. If the molder fails to hold consistent packing pressure, the parts will have varying density and internal voids.

This variation is caught immediately during the high-frequency test, allowing the operator to adjust the process before producing a large batch of defective parts.

Failure Mode

Environmental factors like humidity or temperature changes during the product’s operational life can degrade the structural integrity of a polymer component. A gradual resonant frequency shift in a molded sensor housing indicates that the plastic has absorbed water or suffered micro-cracking from fatigue. When moisture enters the polymer matrix, the electrical capacitance rises, leading to a permanent drop in the resonant frequency.

This change signals that the component has reached the end of its useful life and requires replacement to avoid system failure.