Mineral Insulated Cable Routing Strategies for High Temperature Mould Telemetry
Recessed MI cable routing with thermal expansion loops prevents wire pinch, shields noise, and eliminates press downtime in high-temperature moulds.
Expansion Loop
Meaning
Curvature in a heating element or sensor lead provides a mechanical buffer against physical displacement caused by temperature changes. Incorporating an expansion loop prevents the buildup of axial stress in rigid heater assemblies. This design feature is common in hot runner systems where significant temperature swings occur between the ambient state and the processing temperature.
It functions within the elastic limit of the sheath material to ensure repeatable movement.
Stress Distribution
Mechanical loads are diverted away from brittle termination points when the assembly undergoes thermal cycling. The expansion loop acts as a spring that absorbs the longitudinal growth of the metal sheath. Failure to include this feature often results in the shearing of electrical connections or the cracking of ceramic seals.
Such damage occurs because the metal expands faster than the surrounding steel block.
Positional Stability
Proper sizing of the bend ensures the heater remains in contact with the transfer surfaces. An expansion loop that is too large might interfere with other mould components or cooling lines. Precise calculations of the expected growth determine the necessary volume of the relief area.
Installation Radius
Minimum bend requirements for the sheath material must be observed to prevent thinning of the wall. A tight expansion loop can introduce work hardening that makes the metal prone to fatigue. Maintaining a generous radius preserves the dielectric properties of the internal insulation.