Design of a Formable & Heated Insole

Project Objective and Scope:

This project was a unique design idea delivering documentation and research and development for a final year undergraduate engineering process in the design of a “Design of a Formable & Heated Insole”. The design idea was theorized by the group with no ideation help from any other parties. The design focused on creating an effective footbed heating system, specifically for ski boots, and material thermos setting aimed at enhancing comfort during winter sports activities. The project will be carried out with a consideration for implementing two features in footwear that are not available together: foot memory shaping and heating.
The project was carried out during an 8-month period with a core group of 4 members that were each in charge of a different section of the design, delegating responsibility effectively. The group communicated efficiently together as well as externally.
Result of the project consisted to a working model with some minor electrical modifications needed to transition into a developed product. The group conducted market research and found out that no products exist that combine the two features, this along with total pricing was an important factor in the design. Important considerations were taken for materials, manufacturing and assembling to keep the final price minimal. This is in order to develop a final product that would be accessible to a market.

Project Statement

The objective of this degree project is to develop a heated insole that has the functionality of plastic deformation, being able to form to a person's foot and ensure a secure fit. In skiing, the foots constraint inside the ski boot is paramount to a comfortable, secure riding experience. Without a stable, locked in foot, a skier may not be able to properly control their ski, making them prone to injury. Today's market has insoles that can mold to a person's foot, or devices that allow the insole heat up, but not both.
Through defining the functional requirements of the product, a few parameters where needed to achieve the design. To start, the product had to be a similar size to current market options for insoles, being around the 3-6mm range. The Product also had to produce a temperature range that allowed the thermoplastic layer to plastically deform under the forming conditions. The product also had to Produce the heating portably, so batteries would be needed. In order to achieve the temperatures, monitoring and control of the temperature would be needed to achieve the required temperature, as well as safety for the user.
The design process revealed that the temperature distribution along the thermoplastic layer had been nonuniform. To deal with this, a thermally conductive layer would be implemented on the interface on the heaters would allow the temperature to become more uniform along the cross-sectional area of the thermoplastic. To also aid in the uniformity, larger diameter polyimide heaters would be implemented, over smaller ones that meet power requirements.
The design that had been finalized results in a multi-layered product that runs off a micro-controller that monitors temperatures and regulates the heat dependant on the users needs.
Though the insole did not 100% emulate real life parameters, the assumptions that were used still gave confident results for the use case. We were still able to achieve the correct temperature across the thermoplastic and have the design fit within the required thickness.

Methodology

The methodology highlights the engineering implementations used in order to support the results from the project; this section will detail the software and theories applied with the knowledge being gained from university academia.
During the design and development process of the "Heated Insole," various software tools were used to establish strategies for product design and ensure its functionality. The knowledge gained from previous semesters, particularly through courses such as Heat Transfer, Materials Science, and CAD Design, played a crucial role in successfully completing this project. These foundational concepts provided a strong understanding of thermal management, material properties, and the integration of mechanical and electrical components. Additional research was conducted to identify suitable materials, heating technologies, and design features for the footbed heating system. 3D modeling in Autodesk Fusion and SolidWorks was used to create detailed designs and simulations giving for the precise visualization of the footbed and its components. These tools facilitated the optimization of space and integration of the heating elements within the footbed.
For analyzing and optimizing the thermal performance of the system, ANSYS physics modeling software was employed to simulate heat distribution and ensure the even distribution of heat across the footbed. This was particularly important to avoid hotspots and ensure that the footbed maintained comfort while providing effective heating. These software tools, combined with practical knowledge from past coursework, were essential in developing the final design of the heated insole, ensuring both efficiency and practicality in its operation.
3D scanning was utilized to build the reference geometry of the ski boot and foot to use in the thermal simulations.
Photogrammetry is a type of 3D scanning utilizes the images taken using a standard camera such as a DSLR or the camera on a cellular device to generate 3D models by processing overlapping photos taken from various angles around the object being scanned. This method of scanning was used since it can be used on any mobile device with a camera, utilizing the Scaniverse app. This is a convenient method and eliminates the need to source an expensive 3D scanner. We also compared the dimensions of the scan against the object’s dimensions and they within a millimeter of each other.