This project will consist of designing an insole for a shoe consisting of two materials, a flexible/soft material for cushion and a strong material for support. Our initial thoughts are to use FilaFlex, a thermoplastic elastomer, for the flexible material and PLA or ABS to provide strength for the support material. In consideration of the design of the insole, we need to consider:
1. Dual extrusion of the materials and whether the FilaFlex material will work properly with the home 3D printers we have at our disposal. If it doesn’t, we will need to find a new material with properties that will provide the cushion for the insole. We already know PLA and ABS will work in the printers, but the use of the dual extruders will be necessary. Otherwise, the support and flexible components can be printed separately and adhered together afterwards.
2. Development of a CAD model with parameters that can be quickly changed for different foot/shoe sizes.
3. Various loading conditions in walking and running, such as being on the heel, toe, and bending in the arch. A force plate will most likely be used to get values for these forces and software will be used to optimize the support structure to give optimal performance (especially in bending at the arch) while minimizing support material needed. There are two ways to consider various walking/running loading conditions with our design. Since the PLA material will provide the arch support, a simple in-vivo standing test can prove it’s strength. The part can be placed under the arch in the shoe and the feel of how it will affect in-shoe foot positioning can be subjectively measured. Additionally, ANSYS can be used to apply a force load over the top surface of the PLA CAD model to predict stresses in the part.
4. The bonding of the two materials together to make sure the materials adhere to each other during the print.
5. Post processing and method of heating up the FilaFlex material to mold it to the specific foot that it will be fit to.
Fuse Deposition Modeling (FDM) is the logical choice for our project, as it is the most inexpensive platform, although using TPE for SLS would provide far better surface finish, as well as eliminating the need for support structure. Binder jetting with premixed flexible and support material in an ideal ratio could be an option for future development, but with the materials at our disposal, FDM is the best option.