Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
- Scaled Prototype Mold Testing - 50%
- Test functionality of molds - have sub-scale molds, need more testing
- Mold Selection - 100%
- Decide Vacuum or Rubber - chose vacuum formed molds
- Date is set to test, need to create mixes
- Concrete Mixture Testing - 100%
- Decide on mixtures - have three initial mixes
- Test samples - doing both compression and flexural tests
- Full-size Prototype - 25%
- Create full size prototype - have materials ready, need CNC time
- Risk Assessment - 100% for this phase
- Our team accomplished the following tasks:
- Gathered materials to create the positive molds (plywood, wood glue)
- Started the process to have the positive molds machined in the construct
- Set times to create the test samples and complete the testing of our concrete mixes
- Visited Manitou Concrete on Jefferson Rd and inquired about lightweight concrete mixes
- Created a prototype of how we are going to cut and string the bottle pieces
- Completed necessary paperwork and CAD files
Prototyping, Engineering Analysis, Simulation
- The photo shown above is our current progress on the positive molds. Cody gathered some plywood from his work and we were able to glue them together to get a thicker material to machine. We will create the positives in sections to minimize the amount of waste on the plywood.
- Dylan has been working in the construct on the machining of our positives and is currently working on creating tool paths.
Biochar and Aggregate Sizing Fixture
- As a group, we experimented with different concepts for sizing the biochar and aggregate. A while back Cody made a fixture that would go over a 5-gallon bucket with wood and a screen, that you simply pour the material on top and shake it through the screen. The problem with this is that having someone shake the screen for hours on end takes a lot of time and isn't ergonomically friendly. Our solution looks something like the CAD file above, with three separate size screens for each desired material size. The biochar and aggregate can be sized with this fixture.
Bottle Stringing and Cutting
- Above is our thoughts on the process for stringing the bottles and cutting them. We created a fixture with a 5-gallon bucket and a 1/2" diameter PVC pipe. The way that this fixture works is that you can set the bottle up in the stringing device, and then feed it through the side of the bucket and around the pipe. The worker will wind up the string on the pipe, which is stringing the bottle at the same time. Once the string is wound up on the pipe completely, the worker will take shears and cut the string all at once by putting the shears in a slot cut on the pipe.
- Finished product of what the strings will look like after they have been through the stringing and cutting process. These are ready to go into a mix.
- A simple cost analysis on the stringing fixture with shears included. In Haiti, the 5-gallon buckets will most likely be free, and the pipe will most likely be scrap pipe found laying around. This is what it cost me to make this prototype.
- We started thinking about how we want our manufacturing facility to flow once our product and prototyping are complete. The bottle stringing and biochar/aggregate sizing are two subsystems that can be working in parallel. Once the material has moved through those systems, it can be stored in finished goods inventory. The molds will be located near the sized/cleaned materials so that when an Arborloo is ready to be made, workers can go to one centralized location to retrieve materials and molds. Then there will be an area for concrete to be mixed and poured and cured.
Talking With Experts
- Manitou Concrete
- John Topping spoke with us about touring the Manitou plant on Jefferson along with presenting us with lightweight concrete ideas.
- Jim Wagner gave us a plant tour of Manitou and showed us the operations they undergo on a daily basis.
- Faro Industries
- Alan Hubbard spoke with us about different
methods and materials for vacuum forming:
- He had some concerns on the design
- Gave us advice on what type of materials (ABS & HDPE)
- Thickness of material we could form with
- Once we have a positive, Faro will help us with vacuum forming
- Alan Hubbard spoke with us about different methods and materials for vacuum forming:
- Orcon Industries
- Rick Flannagan spoke with us about the material they use to vacuum form in their facility which is called a Red Ren.
- Construct - CNC and Vacuum Forming - Mike Buffalin
- Availability of free machine time and faculty assistance confirmed
- Designs have been checked for manufacturability
- Scrap material for prototype mold masters has been acquired
- Material Suggestion (⅛’ ABS sheet preferred)
- Local supplier suggestions - looking into soliciting donations
- Biochar - Kathleen Draper
- Kathleen Draper creates biochar for herself to use in various different application. She is willing to provide us with biochar when needed for testing purposes.
- She also invited us to come watch how she makes biochar to understand the process.
- Professor Gupta - MECE
- Concrete Flexural Test
- Confirmed Strengths Lab could not be used to test
- Professor Johnson & Alexis Rich - Packaging
- Confirmed we are able to test with their equipment
- Time set for after Thanksgiving
Full transcripts of all expert contacts can be found here.
Feasibility: Prototyping, Analysis, Simulation
- One of the focuses of this phase was consulting with
experts on concrete and vacuum forming to help mitigate
the risks involved with our design choice. It is
difficult for us to know at this point if our design will
be feasible, but we have taken all the steps that we can
to increase our odds.
- A concern that was brought up by the experts was how our rings are designed and how they rely on friction and sheer weight to hold them in place. The contact used the example of a crock pot, if you push the lid down in the front, the back of the lid will slide up into the air and your hand will go in the pot. The solution to this potential problem is creating a lip or key in the design of the rings, but we are hoping it won't come to this as it will require us to test the entire structure of the rings.
- Sam has been researching ASTM Standards for concrete testing that might be applicable to our project. He has validated the use of earlier team's molds, calculated the amount of materials for test materials, created a test plan, and set a test time. We will be pouring these test samples in the coming days and will test November 30th.
- The two charts shown above are the justifications for how we chose our mold type and material, as well as our positives to mold over. We are moving forward with vacuum forming over wood.
- Here we have a BoM detailing what it will cost us to make an Arborloo. We based this information off of volumes of each material and how we would acquire it here in the U.S.
Drawings, Schematics, Flow Charts, Simulations
- Faro Industries suggested ABS as our material
- Performed initial feasibility of loading on flat sheet, with fixed edges
- Max displacement in center was .97”, deemed acceptable
- Next performed simulation on beam ring mold
- Fixed ground surface, no penetration contact between mold and ground
- Max displacement evaluated as 1.926e-3 in
- Number is extremely small, most likely issue with simulation parameters
Preliminary Bill of Material (BOM)Based on the system design and initial feasibility tests, the preliminary Bill of Materials shown below was generated.
As can clearly be seen, and highlighted in yellow above, the largest cost is the material required for the vacuum formed molds. Such a large purchase is a risk that must be considered, as if the material doesn't work as expected or other issues arise, a large portion of the budget will have been lost. To mitigate this risk, the team is looking to obtain material donations, as well as performing additional small-scale feasibility tests to verify material performance. Most up-to-date BOM can be found here.
Test PlansOur complete test plan for our concrete specimens can be found here. Official test plans are still being developed for the other subsystems. The basic templates are shown below.
Concrete MixturesThis test plan is intended to determine the ideal concrete mixture for our required use.
- Prep Materials and equipment
- Measure material by weight
- Mix dry ingredients together, then add water
- Place molds on vibration table and pour
- Fill in corners on molds
- Scrape excess off top
- Leave in molds to set for 7 days
- Let cure in MSD Booth for 7 days
- Measure weight, test flexural strength, test compressive strength
Biochar ProductionThis test is intended to determine two separate factors. Which kiln process is most effective for use in Haiti, and how well agricultural waste works as material for biochar.
- Prep materials and equipment
- Add material to kiln
- Run kiln process
- Measure effectiveness of process
- Determine most effective materials
Bottle Stringing/ChoppingThis plan is intended to test the viability of different chopping and sizing methods.
- Prep materials and equipment
- String multiple bottles
- Cut bottles with chosen method
- Establish desired method
Aggregate SortingThis test is intended to determine the efficiency of our proposed sifting system.
- Prep materials and equipment
- Add material to sifter
- Sift material with different methods
- Calculate efficiency of sifter with each method
Aggregate MeasuringThis test is intended to determine which method of aggregate measuring produces a more accurate mix, and can be used in Haiti.
- Determine accuracy of different measurement methods
- Test ease of use for proposed methods
Risk AssessmentTo this point in our project, our risk assessment has remained relatively unchanged. However, a new resource risk was added, associated with the cost of purchasing the desired ABS plastic sheets. Mitigation actions are currently being planned and implemented. Additionally, risk number nine (9) has had the associated likelihood reduced as a result of our theorized mixture density. When the ring weights are calculated with this density, they are light enough (<25 lbs) to carry with minimal risk of injury.
Risk assessment document.
Design Review Materials
Plans for next phaseShared team vision can be located at the top of Detailed Design.
The individual team visions can be viewed here.