P19037: Skreppa Modular Shoe

Subsystem Build & Test

Table of Contents

Team Vision for Subsystem Level Build & Test Phase

What did your team plan to do during this phase?

During this phase our team planned to construct at least a first iteration prototype of our subsystems. We planned to have multiple prints of our joining mechanism to experiment with different molding techniques. We planned to construct at least one upper prototype out of muslin. We also hoped to have a first print of our outsole completed.

What did your team actually accomplish during this phase?

During this phase we found many unknown roadblocks however we were able to print a third iteration of our joining mechanism, resizing and adding a dovetail shape to the slide. We tested the properties of instamorph for molding and binding our joining mechanisms to our shoes. We set up and practiced operating our sewing machine and created five iterations of an insole. We created both a low top and high top upper pattern using our last. We also found a source for our outsole and have decided to 3D print the first iterations. Our team also entered the RIT business model competition and began working on our paper for Tiger Tank.

Visual Representation of Work Completed

With this new build phase, the team delved deep into figuring out the new sewing machine & learning what worked and what didn't. The team has designated Lydia as the sewing machine maestro - as seen in the middle of work below.

Lydia Sewing

Lydia Sewing

The shoe inserts became the easiest thing to create and iterate on while still learning how to use the sewing machine. From right to left, you can see the different versions that were created. Starting at the farthest insert to the right, you are able to see an example insert that was taken out of a donated shoe. This was used as a template to see the rough idea as to what's expected. Next, you see a simple padded & quilted insert. The main addition to this one was a cheap and thin foam layer that was found in the salvage shelves on the MSD floor. This had made the team realize that padding & quilting in strategic places will allow for better support in key areas of the foot. Moving on, you see a more intact insert that has diagonal quilting. This was filled with a recycled pillow fill that was found also on the salvage shelves of the MSD floor. This allowed the team to compare and contrast the differences in foam vs. pillow fill and make decisions moving forward. Next, you'll notice a migration to a more complete insert made with an eggshell foam similar to a bed topper - in addition of a cutout for more arch support. Finally, the white & blue insert is the most recent iteration - with a blend of the eggshell foam where the majority of weight is placed, and the pillow foam in the arch support area.

In future iterations, the initial cutout will have more space for the arch support that will allow it to actually support the arch.

New Shoe Insert Progression

New Shoe Insert Progression

The team had decided on a slide & pull mechanism that will work jointly as the final mechanism. This will allow the user to slide in the heel with a track, and pull the toe cap over the toes of the upper to lock it in place. With this decision, the team needed to start designing and testing the sliding mechanism. Below is a photo of Version 1 and Version 2 of the tracks. Version 1 had a very tight tolerance and did not allow for the instamorph to form neatly around. Version 2 seemed to like the instamorph a bit too much, as it became permanently adhered. This created various risks that is mentioned in the following sections. The failure of V2 caused the team to decide that the slide may need to be printed for the prototype, with future iterations possible. This led to the creation of a smaller slide that would be attached - rather than be a mold. The team is now working with Version 4.

Mechanism Versions 1 & 2

Mechanism Versions 1 & 2

Finally, with the large volume of shoes that were donated, the team wanted to utilize them as best as possible. Some shoes had their laces taken, some were cut in half. Ultimately, this led to some shoes being deconstructed as seen in the photo below. These former boat shoes will now have a future use as the prototype for Skreppa.

Deconstructed Shoes

Deconstructed Shoes

Test Results Summary

In this phase we added test plans for infill %, sliding lifecycle, fabric strength, stitch strength, and slip resistance. We tested fabric strength and stitch strength. Unfortunately the fabric we chose to test stitch strength with failed before any of our stitches at between 90-100N. The dark sunbrella fabric we hope to use in our final prototype had no deformation at load cell maximum.

Tracked data for the stitch testing can be seen here.

Additionally, test plans & results can be found in a live spreadsheet here.

Risk and Problem Tracking

For this next phase, the team was presented with the manifestation of a few risks that were already expected. Specifically, a few members needed to miss team meetings to interview on site for full time positions. Additionally, the team also discovered a few new risks to account for. These risks were notably more physical construction based, which is to be expected with prototyping & building. Specifically, four (4) more risks were added to the live spreadsheet.

Working Prototype

Ultimately, at the end of this MSD Project, we want our customer to be satisfied with the work completed over the last two semesters. This translates pretty simply to "make sure the whole thing at least works". Overall, this is a fairly large aspect to fail on, so the team has decided that it will be potentially necessary to meet outside of class time to put in that extra effort to hopefully complete a working prototype. Given that the team now has a work space that is separate from the main work floor of the 4th floor of Gleason, it's easier for us to meet separately.

Integration of Sustainable Materials

At the soul (or sole) of this project is making sure that we are cutting down on shoe waste - instead of adding to it. As a team, we need to integrate sustainable processes & materials throughout the shoe itself. To go against this is a large derivation of the original mission statement and therefore the project. Therefore, this has a higher weight than most other risks. Our way of mitigating this is making sure that every step we take, we consider the materials & processes that will go into the final shoe.

Chosen Stitch Fails

The new Brother sewing machine that we purchased is a lovely addition to the Skreppa Team - especially due to its capabilities of doing over 20+ types of stitches. With great options, come great choices. We needed to consider all of the risks associated if we should choose wrong. Although the risk of this occurring is pretty low, we wanted to make absolutely sure. From this, Haley & Lydia began to test the different strengths of the potential front runners of stitches to use in the final shoe. More information can be found below in the test results section.

3D Printed Part Melts

When implementing the 3D printed mold, we knew that we wanted to use Instamorph to create a positive and negative form of the track. Instamorph, with it being a thermoplastic, needs to be heated up to around 200 degrees (F) to become malleable. Unfortunately, we quickly learned that the Instamorph likes to adhere to the PLA molds immediately. From this, we imagined that since PLA prints around 200 degrees (C), submerging it in lower temperature water shouldn't be an issue. We were wrong, which led to this new risk. PLA of a certain thickness will warp and melt when submerged in hot water. In order to avoid this in the future, we will need to rethink how we will be creating the sliding mechanism onto the shoe.

New Risks as of 20 February 2019

New Risks as of 20 February 2019

For easier viewing, the live spreadsheet can be viewed, in full, here. Additionally, a new graph was generated to somewhat keep track of running risks and their relative weights. This allows us to make sure that we are not ignoring any risks that larger than they seem.

Various Risks for Skreppa

Various Risks for Skreppa

Regarding the risks that have manifested themselves as genuine problems, the Skreppa team has been working diligently to keep track of any problems that arise from here on out. As of late February, the problem tracking document looks like the image you see below. During this phase, we learned of new problems regarding the manufacturing process that will effect our final product. Additionally, we found that the material we planned on using for our outsole connection - Instamorph - has different problems associated with it that will take some finessing. The live spreadsheet, that will be updated throughout MSD II, can be found here.

Problem Tracking as of 20 February 2019

Problem Tracking as of 20 February 2019

Functional Demo Materials

Plans for next phase

As a team, where do you want to be in three weeks at your next demo?

The Skreppa team will be continuing on the construction of the upper portion of the shoe with the materials we’ve identified as the best for our shoe. The team will also implement mechanism to the bottom mold to establish a working prototype. The will continue to test our subsystems.

As an individual on the team, what are you doing to help your team achieve these goals?

Lydia Yeckley - 3 Week Plan

Nick Amato - 3 Week Plan

Haley Gallagher - 3 Week Plan

Mickey Evans - 3 Week Plan

Peer Evaluation for End of Phase

The completed peer evaluation for the Subsystem Build & Test Phase can be found here.

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