Subsystem Build & Test
Team Vision for Subsystem Level Build & Test PhasePhase Objectives:
In this phase the team would like to accomplish these tasks:
- Purchase materials for
- Test Samples
- Analyze test results and finalize tile mix
- Test foams and insulating coverings
- Find final molding solution
- Purchase Mold materials
- Create a plan of attack for Dan’s Trip
- Evaluation of manufacturing requirements
- Further integration of the Saunder’s team
In this phase, the team has divided these goals into these themes and assignments:
- Matt - will be leading the testing of samples as well as deducing conclusion results
- Derick - will be leading project management tasks, working with sauders team integration and guiding team discussions.
- Dan - will be in in charge of material design, research and mold creation
- Connor - will be in charge of researching risks and planning manufacturing requirements
Updates - Where are we?Pulse of the Project
With only one and half weeks until Dan leaves for his trip to Nicaragua, the Engineering team has been working on making sure that there are a few molds created. As of right now, some updates include:
- Finalization of Mix, based on feasibility of strength tests and cost projections
- Choice of Mold style, based on materials testing performed for the plastic forming process
- Consciousness of choices based on the status of the business
- Frame needs to be expanded, with the first steps being taken already
- Test Roof has been priced out, some materials acquired
- Hess pumice, as promised has shipped 40 lbs of 1/8 inch crushed Pumice
From the sound of Ricardo’s E-mails, it seems that the Pumice Roofing Company that Ricardo had mentioned is actually still in production, but based only on orders. There has been no signs of marketing since 2013, however he speculates they still work on tiles whenever there is a request.
Below is the Subsystem Decomposition showing what features the team has been working on this phase:
Saunders UpdateBelow is an update coming from the Saunders team. Karina will be explaining the following screenshots of an extensive spreadsheet outlining the business’s feasibility:
Materials and Costs
Some notes on the matter include:
- Costs are inflated in the current model since we were working with unverified costs.
- Some of the costs were educated guesses.
- Kellan Morgan sent us his verification of costs and we will update the model shortly.
- The projections are very conservative in terms of forecasted demand.
- The following steps include customer discovery and market research.
Test Results Summary (DOE)Below are the results comparing the different cure methods used. All of the samples in this graph didn't have any reinforcement in order to directly examine the effect of the cure. Based these results, it was determined that water curing is the best method.
Based on mixing observations and test results, we have decided to go with the Higher (40% Pumice, 30% Sand, 30% Cement) Ratio. While mixing the lower and higher ratio, it was observed that both mixtures contained too much water. Concrete has been shown to have an inverse relationship between water and strength. The reason for the equal ratio's performance was due to less water being used.
Below are the results comparing the different reinforcements used in the samples. All of these samples were water cured since it was determined to be the best cure method. These results show that the plastic string had an adverse affect on strength while the onion bag reinforcement maintained most of the strength of the concrete.
On most occasions, the onion bag and plastic string was able to sustain a load after initial failure. The plastic string was able to maintain a larger load after initial failure the onion bag. Based on this behavior, we determined that the best reinforcement method is plastic string placed randomly in one layer near the bottom of the tile.
All of the testing data can be found here.
Test RoofCost has been mitigated from the test roof design
Mold Form TestingIn order to make the mold, we planned to thermoform plastic over a carved piece of foam with a protective coating on it. In order to determine the best combination of foam and coating, we thermoformed plastic over several test samples.
Based on the results of this test, the foam insulation board with epoxy was the most viable option. However, we would need to spend too much money on epoxy in order to coat the whole surface. We have instead decided to carve a negative out of the foam and use it to make a positive out of our leftover plaster, which we will then vacuum form over.
Tile BuildWe built a tile using the last team's equipment, but with our pumice concrete mix. We did this in order to get used to the process of making a tile, and to take note of any problems that may occur when we eventually build our tiles. We learned the following lessons:
- Mix buffer of 1.35 produces the right amount of concrete
- Water mixing needs to be done very carefully in order to achieve the right viscosity
- Too much water hinders the concrete's ability to keep shape of the nubs
- Our tile is indeed significantly lighter than the previous team's tile
- Crushing our pumice to size is too inefficient; ordered more pumice at the right size
Mold DesignMold shape remains unchanged. CAD simulations and mold material tests give us confidence that a 1/16" piece of plastic will be strong enough for the mold. However, since we already have 1/8" plastic, we will be using this for our first three molds and then possibly making thinner molds after spring break.
ManufacturingOutline Below is an overall flowchart of our process. Please note the changes made to include the plastic string processing and layering into the tiles.
Recently sent this document to Saunders team so they could develop cost estimation for the cost of these materials.
Manufacturing Time Estimations
Times were gathered from the Eco Sur South videos of tile production & other sources for estimation.
Grinding pumice does not have a time because the team is discussing the possibility of having enough pumice for next weeks production grinded to size at the end of each week to be ready for production the following Monday.
Based on the estimation of 10 minute lead time of one tile, we can assume that if one person ran the system alone they could produce at least 6 tiles an hour= 42 tiles in a 8 hour workday (8hrs.-1 hr. for breaks & lunch).
Note: This number is valid for if the person did not have to transport the tiles, grind any pumice, had 100% yield, no downtime of machines, or any other subprocesses that would keep the facilities production at a constant. Due to these additional factors, production would not be met with only 1 worker creating tiles.
Space AnalysisCalculated the amount of space needed for each curing area.
-Business will have a total of 40 molds in manufacturing system (Maximum throughput of 40 tiles per day)
-Tiles in 7 day water cure and 21 day air dry cure are leaned on one another at an angle of 10 degrees.
-First in First Out (FIFO) process will be used for 21 day air dry cure method (oldest tiles will be sold & used first)
1 Day Cure Inside Mold:
Cure Inside mold requires a minimum of 15 ft.^2.
Recommend the space is a 5'x4' area (20 ft^2) where the molds will be stacked into two separate piles (maximum height of 3.125 ft.).
7 Day Water Cure: Requires a minimum of 61.25 ft.^2.
Recommended pool space of (3'x23') (69 ft.^2) or two (3'x12') (72 ft.^2) pools. 1 row of tiles has a width of 1.5 ft. (buffer of 2 in. for each row, two rows in pool). Pools being a maximum of 3 ft. in width allows for easy picking up of watered down tiles from either side of pool.
Height of water in pool must be at least 2 feet to completely cover tiles (2in. of extra water)
Note: In next phase we will preform a test to determine whether or not the tiles can touch each other during this curing method without forming to one another.
21 Day Air Cure: Requires a minimum of 227.5 ft.^2.
Recommended space of two (6'x20') sections (240 ft.^2). (Space for 21 days of production of 40 tiles a day + 200 finished curing tiles (5 days of max production))
-The 6 ft. wide sections will have a 3 ft. open space as aisles on both sides of itself ~ 1 middle aisle and two side aisles = three (3'x20') (180 ft.^2) totaling to be 420 ft.^2 of space needed.
-This makes it easier for storage and picking of tiles because workers will only have to pick or place tiles at a max of 3 ft. away from their body (2.25 ft. if holding center of tile).
-Tiles will fill two rows at a time to one side of the aisle (two 1.5 ft. rows) picking and placing tiles so that they always have space to move their center of gravity closer towards where the tiles must be placed or picked.
Standard Work: The team is planning on focusing in on the specific details for work procedures more in next phase. For example, the idea to wrap colored rope/string around the sections of tiles produced each day. These colors will correlate on a whiteboard inside the facility that keeps track of the time groups of tiles have been both water curing and air curing. -Number of workers & roles of workers
Costing and Material Requirements PlanningA Spreadsheet to outline Demand and Materials Demands was created to help the business students understand different values and quantities that are important to the project. The first part of figuring out the materials requirements was to understand the quantities of demand. Below outlines the Worst Case Scenario, or WCS of the Demand. We can see a yearly Demand of 4872.
To figure realistic scenarios for a business and manufacturing model, we worked with a few assumptions, outlined below. An important note is that the manufacturing process will have defects, and we want to plan to be at worst a 3 Sigma process, or having less than 66,807 defects per million opportunities, or less than 6.7 percent of our tiles being damaged or broken at any part of our process.
The following table focuses on the dry material weights and volumes per tile, per roof and per year. This can be used by the business students for pricing, as well as the Engineering team for manufacturing and space requirements.
The following table also incorporates other materials required in the roof, including the water and the wire used to wrap around the c-beam supports.
Risk and Problem TrackingRisk Assessment
Problem Tracking Below is our problem tracking table. This tool is useful in conquering some of the obstacles in an organized manner. Note that not all problems have been solved yet.
What's been done
- Secured funding from Dean's Office
- Meeting with Dr. Robinson on Friday
- Contacted MSD Office
- Created rough itinerary
- 3/11- travel to Managua, late arrival, dinner in Managua
- 3/12-Travel to Tisma and make contact with tile manufacturer
- 3/13- travel to El Sauce and purchase materials for manufacturing tiles, begin manufacturing tiles
- 3/14 - 3/16 manufacture tiles
- 3/17 - return to Managua
- 3/18 - Fly back to the US
What still needs to be done
- Plane tickets
- Finish modifying frame
- Finish itinerary
Backup PlansIf molds are not made by the time I go on my trip, I will focus on experimenting with making molds using materials in El Sauce
Plans for next phaseThe team will focus on these deliverables before Dan’s Trip:
- Forming the Mold
The team will focus on these deliverables in the next Phase:
- Expand the Frame
- Creation of the top tile mold
- Create Tiles
- Begin building the test frame
- Official entry into the Imagine RIT
- Integrate the Business team further, work together to cut costs
Below is a Gantt chart for our plan.