Induction Shrink Fitting for Precise Aircraft Engine Assemblies
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Solution Overview
Problem
Existing shrink fitting techniques for aircraft engine assemblies are not practical, predictable, and can damage sensitive parts, while also increasing manufacturing costs due to challenges in temperature control and production rate optimization.
Innovation Solution
An induction heating system with a controller and tooling units, each equipped with an induction coil and holder, uses a heating recipe to precisely control temperature and power supply, ensuring efficient and predictable shrink fitting of male and female parts, minimizing damage and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional resistance heating or gas heating is used for shrink fitting, then the equipment is simple and easy to operate, but the manufacturing precision and consistency of interference fits are poor due to lack of process control
Solution Approach 1:
The patent replaces conventional resistance heating elements or gas heating systems with an induction heating system. The induction coil generates an electromagnetic field that induces eddy currents in the workpiece, heating it rapidly and precisely without direct contact. This substitution enables precise temperature control through programmable parameters (heating time, power level, cooling rate) while maintaining operational simplicity through automated control, thereby achieving consistent interference fits without the complexity of manual heating processes.
Solution Approach 2:
The patent implements precise control over heating parameters including temperature, heating duration, and cooling rate. By programmatically adjusting these parameters based on the specific workpiece and desired interference fit, the system achieves consistent manufacturing results. The computer-controlled induction heating system allows optimization of each parameter independently, ensuring the workpiece reaches the exact temperature needed for shrink fitting while controlling the cooling rate to achieve the desired residual stress state.
2Manufacturing precision
If manual heating methods are used, then the equipment is simple, but the heating uniformity and temperature control are inconsistent leading to variable interference fits
Solution Approach 1:
The patent replaces manual heating methods with an induction heating system where an electromagnetic field directly induces currents within the workpiece material. This internal heating mechanism ensures uniform temperature distribution throughout the workpiece volume, eliminating the temperature gradients and hot spots associated with external heating methods. The computer-controlled system automatically manages the heating process, providing consistent results without requiring manual intervention or complex manual control procedures.
Solution Approach 2:
The induction heating system utilizes the workpiece's own electrical conductivity and electromagnetic properties to generate heat internally. The alternating magnetic field from the induction coil induces eddy currents within the conductive workpiece, and the workpiece's own resistance to these currents generates the heat uniformly throughout the heated zone. This self-heating mechanism eliminates the need for external heat transfer media and ensures consistent, uniform heating without manual adjustment.
3Adaptability or versatility
If a single heating system is used for multiple assembly types, then the device complexity is reduced, but the adaptability to different assemblies is limited
Solution Approach 1:
The patent divides the heating system into separate, interchangeable tooling units, each configured for a specific assembly type. Each tooling unit includes a custom-shaped induction coil, holder, and positioning fixtures tailored to the geometry of its target assembly. This segmentation allows each unit to be optimized for its specific application while maintaining simplicity. The modular design enables quick replacement of tooling units between different assembly types without requiring reconfiguration of the core induction heating system or control computer.
Solution Approach 2:
The patent creates a universal induction heating platform that can accommodate multiple assembly types through interchangeable tooling units. The core system (induction power supply, control computer, induction coil holder) remains the same and serves all assembly types, while the specific tooling units provide the necessary adaptability. This multi-functionality approach allows a single base system to handle diverse assemblies by simply changing the tooling unit, combining the benefits of simplicity with versatility.
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 enables faster, more precise, and controlled shrink fitting of aircraft engine parts, reducing manufacturing costs and ensuring reliable assembly without part damage, by using a programmable logic controller with PID control to manage power and temperature.
Implementation Method 1
An induction heating system can be adapted for shrink fitting a plurality of different assemblies (30)
Implementation Method 2
heat the workpiece (36) to a temperature above its transformation point so that the workpiece (36) expands
Implementation Method 3
cooling the heated workpiece, thereby contracting the heated workpiece
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3C
AI summary
An induction heating system can be adapted for shrink fitting a plurality of different assemblies (30). A plurality of tooling units (26) associated to respective ones of the assemblies (30), each one having an appropriately configured induction coil (32) and holder (34), can be provided. A computer can be used to control the delivery of electrical power to the induction coil (32) in accordance with a heating recipe, and can be provided with an input device for inputting an assembly identifier allowing the computer to operate the control based on the right heating recipe.