Induction Tunnel for Wax Thermostatic Elements Testing

Application: Material research and testing

Industry: Automotive; HVAC and Appliances

Application Objectives:
An automotive thermostat manufacturer needed a faster, more repeatable way to qualify wax thermostatic elements during quality testing. The existing electric furnace was slow and could not hold temperature accurately enough for a reliable stroke check. UltraFlex was asked for a compact, automation-ready alternative that reaches the stroke-activating temperature across all five element types and sustaining line throughput of 45–60 parts/min.

The challenges:

• Reach and hold the target temperature for each part type (49 °C to 110 °C depending on part type)
• Sustain a line throughput of 45–60 parts/min
• Run unattended inside an automated handling line

Material:
Wax elements for thermostat assembly

Key parameters:

• Element diameter: 20 mm to 32 mm
• Maximum temperature: 110 °C
• Heating cycle: 60 s maximum
• Duty Cycle: Continuous

Equipment:

• Induction heating system: Ultraheat SMT-5/200 + Heat Station: HS-n5
• Coil: custom segmented tunnel coils, two- and three-zone
• Additional tooling: RoboStand handling stand, IR thermal camera, adjustable tunnel head, stroke test station

Process:
UltraFlex engineers conducted extensive tests using UltraHeat S5 Series
systems with segmented tunnel coils on a RoboStand handling setup. Each part (a metal cup assembly filled with thermostatic wax) was heated inductively while pin stroke was measured, so wax expansion could be read directly rather than inferred from surface temperature. Dual- and triple-zone configurations were simulated and then tested on real parts, splitting the cycle into preheat, hold and final adjustment. Power and timing were tuned per alloy to keep the temperature drop between zones to a minimum.

Results and Conclusions:
Segmented multi-zone inductor was used: the first zone brings the element rapidly to its activation temperature, the second holds it long enough for the wax to expand fully, and a third zone in the extended configuration prevents heat loss on the way to the stroke test station.
The multi-zone approach reached the required pin displacement inside the 60 s cycle while remaining compatible with continuous automated movement — confirming that induction can replace furnace heating in this quality check, at line rate and with power drawn only while a part is in the coil.

Reference Info: AR3464-9007