Induction-Heated Curing Tools with Curie-Point Self-Regulation
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Solution Overview
Problem
Existing induction-heated tool systems for plastic fiber components in the aerospace industry face issues with uneven heating, excessive temperature gradients, and thermal expansion, leading to potential damage during curing due to the use of ferromagnetic materials with Curie temperatures matching the curing temperature.
Innovation Solution
A tool system comprising a thermally dimensionally stable material with a low thermal expansion coefficient and a susceptor element made of ferromagnetic material with a Curie temperature corresponding to the target curing temperature, combined with an induction device to generate an alternating magnetic field, ensuring controlled and even heating without excessive temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ferromagnetic material with Curie temperature matching curing temperature is used for tool part contact surfaces, then temperature control is improved, but thermal expansion increases significantly
Solution Approach 1:
The tool part is divided into two functional segments: a base material providing dimensional stability and a separate ferromagnetic coating layer providing temperature control. This segmentation allows each segment to perform its specific function without compromising the other - the base material maintains low thermal expansion while the coating regulates contact surface temperature through Curie point effects
Solution Approach 2:
The tool part uses a composite structure combining a thermally dimensionally stable base material with a ferromagnetic material coating. The composite design enables the tool part to exhibit both low thermal expansion (from the base material) and self-regulating temperature control (from the ferromagnetic coating that loses magnetic properties at the Curie temperature, reducing eddy current heating)
2Speed
If induction heating is used to heat tool parts, then heating speed is improved, but uneven heating and excessive temperature gradients occur
Solution Approach 1:
The ferromagnetic coating is applied specifically to the contact surfaces where temperature control is critical, while the bulk tool part material maintains its dimensionally stable properties. This local application of ferromagnetic material ensures that induction heating effects are concentrated where needed for temperature regulation without causing excessive overall heating or temperature gradients in the tool part
Solution Approach 2:
The ferromagnetic coating changes its magnetic properties at the Curie temperature, which directly alters its electrical conductivity and eddy current absorption characteristics. This parameter change provides automatic feedback control - as the contact surface approaches the target temperature, the coating loses ferromagnetic properties, reducing energy absorption and preventing overheating, thus maintaining temperature uniformity
3Loss of time
If ferromagnetic material is used for contact surfaces, then temperature self-regulation is improved, but thermal dimensional stability deteriorates
Solution Approach 1:
The tool part is segmented into a dimensionally stable base material and a ferromagnetic coating layer. The base material (such as austenitic stainless steel or aluminum alloy) provides thermal dimensional stability with low expansion coefficient, while the ferromagnetic coating provides automatic temperature self-regulation through Curie point effects. This segmentation allows both functions to coexist without interference
Solution Approach 2:
The composite structure combines materials with complementary properties: the base material contributes dimensional stability and low thermal expansion, while the ferromagnetic coating contributes temperature self-regulation. The coating thickness is optimized to provide sufficient temperature control while minimizing impact on overall tool part dimensional stability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system provides uniform heating with minimal thermal expansion, preventing damage to plastic fiber components by maintaining the tool parts within a stable temperature range, ensuring even thermal energy distribution and self-regulation.
Implementation Method 1
at least one induction device which is designed to generate an alternating magnetic field at least in the region in which the at least one susceptor element is arranged
Implementation Method 2
use inductors and inductively heat the tool parts to the desired temperatures by inducing eddy currents
Implementation Method 3
the susceptor element is formed from a ferromagnetic material having a first Curie temperature corresponding to the target temperature
Implementation Method 4
such a ferromagnetic material loses its ferromagnetic properties at approximately the temperature to which the plastic fiber component is to be heated and absorbs electrical energy radiated by an inductor to a much lesser extent
Implementation Method 5
the tool part is formed from a thermally dimensionally stable material, so that the tool part has a thermal linear expansion coefficient at temperatures in the range between the initial temperature and the target temperature which is less than 1x10^-6
Data Source
Figure 1~2
Figure 3
AI summary
An induction-heated tool system for receiving and heating plastic fiber components from an initial temperature (T1) to a target temperature (T2) is shown and described. It comprises a tool part (1, 1') with a receiving recess (3), wherein the tool part (1, 1') is made of a thermally dimensionally stable material such that, at temperatures in the range between the initial temperature (T1) and the target temperature (T2), the tool part (1, 1') has a coefficient of thermal expansion in the plane of the largest dimension of the receiving recess (3), preferably in all directions of extension of the receiving recess (3), which is less than 10 x 10⁻⁶ K⁻¹, preferably less than 5 x 10⁻⁶ K⁻¹, and more preferably less than 4 x 10⁻⁶ K⁻¹.The tool part (1, 1') has at least one receiving recess (3) for receiving a plastic fiber component, wherein the receiving recess (3) is bounded by a receiving surface section (5) of the tool part (1, 1') so that a plastic fiber component received in the receiving recess (3) can abut the receiving surface section (5). Furthermore, a susceptor element (17) is provided, which comprises a ferromagnetic material having a first Curie temperature corresponding to the target temperature (T2), wherein the susceptor element (17) is arranged on a surface section (13) of the tool part (1, 1') that lies outside the receiving recess (3) and the receiving surface section (5). Finally, an induction device (15) is provided, which is configured to generate an alternating magnetic field at least in the region in which the at least one susceptor element (17) is arranged.