P19037: Skreppa Modular Shoe
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Detailed Design

Table of Contents

Team Vision for Detailed Design Phase

What did your team plan to do during this phase?

Our team plans for the detailed design included prototyping joining mechanism utilizing CAD, 3D printing, and thermoplastics; printing and finishing womens 8.5 last; using tape to create an upper pattern. We also planned to finalize test plans and talk about a reduction in scope.

What did your team actually accomplish during this phase?

Our team successfully completed a We printed and polished our Women's size 8.5 last. In addition to this, we also 3D printed our sliding mechanism; we found that our tolerances were too tight for an appropriate slide. We created a preliminary upper design with the help of our industrial design consultants. We got approval from our customer to reduce our deliverables from 3 outsoles to 2 outsoles by only making a hiking and flat sole and not creating a running outsole. We also began placing orders and receiving items to begin prototyping.

Progress Report

Our team sent out a mid gate progress report to our customer (Bri) and our guide (Jerry) on Tuesday November 20 before we left for Thanksgiving break. The purpose of this email was to show key takeaways, rest of semester plans, and set up meeting times for the end of the semester.

Key Takeaways

Rest of Semester Plans

Detailed Design Review

The date has been set for December 6th at 12:30 pm with the following in attendance

MSD I Tollgate

The date has been set for December 13th at noon with the following in attendance:

Flowcharts, Rapid Prototyping, Current Design

The team met throughout the phase to establish a more solid idea of what we will want in the final shoe. This produced a messy whiteboard full of ideas. However, at the end of the day, a more cleaned up idea was generated. This can be found below:

Whiteboard Meeting

Whiteboard Meeting

Using the whiteboard meeting from above, we were able to derive a total build plan. In order to establish a frame of reference from here on out, a cleaned up first level build plan was been generated in the form of a flow chart. This will allow for better planning in the steps ahead.

Formulated Build Plan

Formulated Build Plan

During the Detailed Design phase, the team began to step towards physically creating what we have been envisioning. This begins with prototyping and purchasing - which is an exciting time for any project. There were two main prototyping projects that were in production during the time of this phase - the shoe last and the beginning portions of the sliding mechanism.

The Shoe Last

Background: In traditional cobbling shoemaking, there is a phrase that goes, “the last is first”. A shoe last is essentially a physical representation of a human foot that assists in pattern making, sizing, and fit. Typically, these are fabricated out of wood or a solid plastic and can cost on average about $70.

The Process: Given that the team is creating a shoe for a Women’s 8.5 shoe, and not a range of sizes, we decided to get our hands on a last. Since the team is not going to be using typical cobbling techniques (i.e. using nails and leather), the possibilities opened up when it came to materials. Since the budget of the team is not expansive by any means, we decided to save as much money as possible and elected to 3D print a shoe. Using an STL file that was acquired from David Cohen (RIT Industrial Design, 2018), we were able to print using a PLA plastic at The Construct. The overall print took approximately 12 hours but the payoff was a complete shoe last that only cost the team $6.60. The last has now been used to create a beginning template of the final shoe.

Shoe Last

Shoe Last

Shoe Last

Shoe Last

Moving Forward: The team is planning to utilize this last for the remainder of the year as not only a frame of reference and measurement, but to test final fits until it is time to present to the customer for the final handoff in the spring.

The Sliding Mechanism

Background: Similar to a male-female sliding mechanism found on a calculator case, the shoe’s sliding mechanism is designed to act as a positive stop at the heel of the shoe. Located on the sides of the foot near the heel, these will eventually be made out of a thermoplastic that will have a low enough coefficient of friction that the shoe will not get stuck when trying to swap outsoles.
Example of the sliding mechanism that we are seeking to base our design off of

Example of the sliding mechanism that we are seeking to base our design off of

The Process: While primitive, the sliding mechanism that is currently designed allows for a proof of concept to be established. It features a positive and negative track that is straight in form. This was designed in the Creo software and was exported as an STL file; the current mechanism was also 3D printed in PLA to save money for the later processes - only costing about $0.21 overall.

1st iteration of the sliding mechanism

1st iteration of the sliding mechanism

Moving Forward: In future iterations, this will be slightly more form fitted that will flex with the outsole material that is selected and will have a slightly wider female track. This is due to the fact that the tolerances in the first iteration were slightly too tight to slide the male track through. This is especially important considering that we plan on using a purchased thermoplastic sheet to form around the track as a type of mold. Additionally, we will want to create a type of 2D funnel at the entrance of the female side in order to help guide the male wedge through.

Finally, here is our flowchart showing where our Engineering Requirements lead into our final design. This is the same chart used in the Preliminary Design Phase since our final design has not altered tremendously since then.

Engineering Requirements Map

Engineering Requirements Map

NOTE: EDGE has been having issues with formatting photos. Using Tortoise SVN, the photo files are shown to be right side up. However, on this level of EDGE the photos appear to be rotated 90 degrees. If you click on the photo itself, the image will appear correctly. If there is any wording that is difficult to read due to this rotation, please click the photo for better viewing

Bill of Materials (BOM)

Current Bill of Materials

Current Bill of Materials

Test Plans

Using the developed engineering requirements, along with the given customer requirements when necessary, we developed test plans to quantitatively analyze user comfort, sole switch time, cost per one pair of shoes, outsole cure time, topsole fabrication time, and water resistance.

Topsole fabrication time and outsole cure time will be simple estimations based on initial prototyping time.

Cost per one pair of shoes will be based on the cost of materials used in one total pair.

User Comfort will be analyzed using human volunteers rating on a visual analog scale.

Sole switch time and ease of use will also be tested with these volunteers.

Water resistance will be tested based on varying height markers by simulating walking in puddles.

For more detailed test plans, our Preliminary Detailed Design module is worth checking out.

Risk Assessment

We have reduced some concerns from the preliminary detailed design by going ahead and printing some supporting materials and purchasing necessary materials as we move into build & test. By getting ahead, we are allowing some slack in our associated timeline as we move forward into MSD II.
Risk Assessment 1-18

Risk Assessment 1-18

Risk Assessment 19-26

Risk Assessment 19-26

For the live document of our Risk Assesment, please click here.

Engineers for a Sustainable World Winter Banquet Expo

In addition to working on The Delta during the week, the Skreppa team made a small field trip on Friday, November 30th to present at the Engineers for a Sustainable World Winter Expo. This expo featured different projects from all over campus and panel speakers from around the Rochester area. Although the theme this year was Sustainable Agriculture, the Skreppa team was invited to present due to our commitment towards using sustainable materials and reducing waste in our landfills.

Additionally, presenting at the expo opened up the floor to hear from people outside of the realm of Multidisciplinary Senior Design - which is always appreciated. Thoughtful questions helped establish points to focus on in the coming phases, while there was a steady amount of interest in The Delta becoming a consumer product on the shoe market.

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Design Review Materials

Plans for next phase

End of Cycle Peer Review

Peer Review For Detailed Design Phase

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