P20414: Indoor Dry Toilet Base

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

The team had hoped to have started the mold for the base of our toilet and even had thoughts of finishing it. We had been pretty set with the materials that we thought we would've have used and wanted to get hands on.

After conducting feasibility testing, the team did not go through with the original plans. The idea of the rubber/silicone mix might work with small objects but scaled up did not make financial sense. The team then brainstormed different ways of creating the mold. This included things like cutting down on the amount of rubber/silicone used, mixing it with other materials, and having completely new designs. The team is now set with a new design, new materials that will be harder to form but are affordable scaled up, and plans on what to do in case the prototype fails or succeeds.

Prototyping, Engineering Analysis, Simulation

The team used last year's toilet base design to design the mold for the manufacturing process. The team needed a prototype to use as reference when designing the mold. Therefore, the following process flow chart was generated.
Mold Process Plan

Mold Process Plan

Below is last year's design that the team relied on.
Previous Team's Design

Previous Team's Design

Below is the 3D printed prototype that will be used to manufacture the mother mold.
3D Printed Prototype

3D Printed Prototype

After Jakob 3D printed the prototype, the team was able to obtain all the necessary dimensions and the scale factor for the life-size toilet. Dimensions and scale factor are core factors in determining what materials the team will be able to purchase and use. These factors show how much material need to be used; therefore, they indicate how much money the team has to spend. In the next section, the team shows the feasibility analysis and justifications conducted to decide what materials to use and why.

Feasibility: Prototyping, Analysis, Simulation

Zyad and Colin performed benchmarking analysis between all the possible materials to be used in the mold.
Mold Material Benchmarking

Mold Material Benchmarking

Despite its cost, rubber was the most promising as it had high formability and reusability. The team decided to perform a feasibility cost analysis on rubber to see if it's feasible to make the mold out of rubber. Below is a report conducted by Zyad, showing all the findings and results of rubber's analysis.

Rubber Feasibility Analysis.

After analyzing rubber's feasibility, the team agreed that rubber costs a lot and would add more cost to the final product, which will interfere with the customer requirements. The team suggests that rubber would be the most effective material to capture all the details and deliver a high quality end product, if the money is available. However, in the scope of senior design, the team decided to modify the mold design so that it would work with other materials.

A new mold design was generated (shown in the next section), consisting of styrofoam on the inside and plywood on the outside. Below are the feasibility analyses for both materials, generated by Colin.

Plywood Feasibility Analysis.

Styrofoam Feasibility Analysis.

Such feasibility analyses helped the team understand how much materials to be purchased for the prototype and life-size product and estimated how much the team will spend out of the budget.

Drawings, Schematics, Flow Charts, Simulations

The team's new design consists of blocks of styrofoam on the inside and layers of plywood on the outside, as shown below. This design, generated by Patrick, significantly reduced the mold cost as foam and plywood are cheaper compared to rubber. Also, the design ensures that the mold is durable and can be reused as many times as possible.
New Mold Design (Top View)

New Mold Design (Top View)

Patrick created a simulation for the mold design to help the viewer visualize how the blocks inside are removed, as shown below.

New Mold Design Simulation.

Currently the new design for the diverter is on hold since the team is waiting for manipulatable CAD files. If those can't be attained the part will have to be completely remade.

Bill of Material (BOM)

After the feasibility analysis was complete, Jakob created a bill of materials to confirm that all expenses and contingencies are afforded by the project financial allocation. The reason the rubber mold idea did not go through was due to it being out of budget of this project. The picture below showcases the bill of materials needed to advance with the current process idea for prototyping. The link for the bill of materials can also be found below.

BOM Excel File.

Bill of Material

Bill of Material

Also shown below is an ideal budget breakdown structure. The team would ideally like to spend $700 on the mold for the toilet structure in total. The current mold structure BOM adds up to around $120 which leaves additional funds in case anything goes wrong. In the future, $400 will be used on the diverter. There is also a risk fund of $400 which might have to be used in case anything during prototyping does not end of working or possible problems with the diverter. All these categories add up to the budget given to the team.

Ideal Budget Breakdown

Ideal Budget Breakdown

Test Plans

Preliminary Proof Of Concept Test

-Set up inner and outer mold pieces in appropriate locations

-Place tape over gaps between the pieces of the inner mold

-Apply releasing agent to walls of the mold that will touch concrete

-Pour concrete in between inner and outer mold

-Check for concrete leaking from any parts of the mold

-Wait for concrete to set, then remove outer part and inner parts of mold

-Check finished base product for inaccuracies

Before all other tests can be run, every step of the test needs to be passed.

Base Mold Timing Test Plan

-Mix concrete prior to test

-Start timer once concrete has been mixed and is ready to pour

-Place all pieces of inner mold together

-Place tape over the gaps between the pieces of the inner mold

-Assemble both pieces of outer mold together around inner mold

-Apply releasing agent on walls of the mold that will touch concrete

-Pour concrete in between inner and outer mold

-Stop timer and record time

-Once concrete has set, remove outer mold pieces

-Remove all pieces of inner mold

-Stop timer and record the total manufacturing time for the base

This test allows us to test our progress on ER1, which is reducing the time to manufacture the toilet base

Jug/Bucket Removal Test Plan

-Place urine jug and 5-gallon bucket into toilet to start

-Begin timer and remove the bucket

-Place another bucket back into toilet

-Stop timer and record results along with a Likert scale from 1-5 on the ease of removal

-Repeat the same process for the urine jug

This process allows us to quantify ER2 and ER3 and is important since the ease of use hold the highest importance on the ER chart.

Risk Assessment

As expected more risks were populated in the risk assessment file. 21 new risks were added in this phase. However 8 risks were also removed from the file as they had to deal with the designing part of the process. Due to vast difference between added risks versus risks that were taken away, the severity has increased. This is due to our new risks having to deal with the mold of the toilet and the materials that were selected. There was only so much feasibility that could be done and experts that could be consulted before the team had to conduct testing themselves. Things like tested how the mold works, is created, defects that could happen by the team can only be figured out by actually creating the prototype.

However since the risks have to deal with mostly the creation of the mold its properties, by the next phase the severity score will be decreased by half. Simply by getting in the shop and creating the mold will figure out around half of the severity risks. A table showing the progression through the phases can be seen below. A live link of the file can also be found here.

Risk Management File.

Phase Progression

Phase Progression

Shown below is an example of the risks that were added for this phase.

Risks Example

Risks Example

Design Review Materials

Relevant Meeting Agendas

10/22/19 Agenda.

10/28/19 Agenda.

Plans for next phase

The goal for the team in this next phase is to finish the small version of the toilet prototype. After completing the small version, this will tell us if the materials and designs the team have selected are feasible which will either lead to changing the material or moving on to the full scale prototype version.

Shown below is the plan for moving ahead in the next 3 weeks before the next design review. Ownership is highlighted with color.

3 Week Plan Flow.

3 week plans

3 week plans

Colin 3-Week Plan.

Zyad 3-Week Plan.

Jakob 3-Week Plan.

Patrick 3-Week Plan.

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