Preliminary Detailed Design
Team Vision for Preliminary Detailed Design Phase
For this phase we planned to execute a few test experiments for our subsystems. One test will be done to see how light effects the larvae when it comes to migration patterns. By completing this experiment we will know if using the LED lights will be a viable option to prevent the larvae from migrating down too far. A prototype will be built to test the feasibility of the revolving door method to remove the waste from the composter. We plan on buying all the materials to do the test experiments. As a group we are formulating a list of materials we plan to use for the composter construction. All of these materials will be put into a BOM along with a detailed budget.
Throughout the time of this phase we have gone through our risks and assessed if they are still applicable and added new ones as they became relevant. We have began the process of creating a 3D model of the final design we plan on building. The materials for the tests have all been surplus materials we have gathered except for the LED lights. Materials used have been documented along with and money spent thus far. Test plans have been updated as more research and prototyping has been completed. research is still being done to find the most cost effective materials to build the final structure with. A plan for the next phase has been established to keep the group on track.
Identified System Redesign Issues
- The cylindrical shape of 19422's prototype is expensive and difficult to manufacture.
- It is also hard to integrate ramps to assist the exiting larvae on a curved surface.
- The auger in 19422's prototype has too steep a slope so when the frass got too wet it just slid out of the bottom.
- Their solution was to put blocks under the opening to keep the frass from falling out while letting the leachate drain out.
- Last year's team 19422 reported that only about 20% of their larvae exited the composter through the top.
- If the sides of the composter get too dry the larvae are not able to stick to the walls and climb up.
- 19422's prototype is about 5 feet tall, so our shorter operators can't see inside or operate the composter.
- A step stool is necessary for shorter operators to use the composter, which is a safety risk.
- Taller operators still need to reach into the composter to remove larvae which is an ergonomic issue.
Engineering AnalysisEach subsystem redesign was evaluated against the continuously updated engineering requirements.
Adjustable HeightEngineering Requirements (By Subsystem).
Feasibility: Prototyping, Analysis, Simulation
Removal System Redesign
- We utilized the Senior Design surplus inventory to find the items needed to execute this test: plywood, 2 5-gallon buckets, and a pvc pipe.
- The plywood was cut in the machine shop to form the auger that moves the frass between the layers of the removal system.
- The 5 gallon buckets were used to create the 2 layers of the removal system. The bucket that made up the top layer had a hole cut in the middle so the PVC pipe could fit through, and a quarter cut out so frass can fall through and be removed. The bucket that made up the bottom layer had one quarter cut out as well so the frass could fall out to the frass collection system.
- The PVC pipe had slots cut into it so it could fit over the plywood auger in order to act as a handle to turn the auger.
- Assembly of the system consisted of slotting the 2 pieces of plywood together to create the auger, slotting the PVC handle over the plywood auger to complete the auger, placing the auger subsystem into the bottom bucket, nesting the top bucket into the bottom bucket and ensuring the hole was 180 degrees from the hole in the bottom bucket, and securing the buckets together with duct tape.
- The test was run by pouring top soil in the top bucket, ensuring the soil didn't leak through to the bottom without the auger moving, and then turning the auger to see if the soil came out the bottom.
- The test results were quite pleasing, and mostly what we expected. The soil did not fall through the system when the auger didn't move. The soil did move through the system when the auger was turned.
- One thing learned is that there was some "caving" in the soil around the hole in the top bucket. The issue is that soil wasn't falling through the hole homogeneously, so we will have to incorporate some sort of fin that attaches to the PVC handle to sweep all the soil from around the entire bin through the hole.
Computer Aided Model
- This should be a less expensive alternative from the design of the same subsystem in P19422 as it will be a manufactured component, rather than something purchased and re-purposed.
- New cost may be incurred by implementing bearings into the system. This cost will not be exorbitant, as bearings are relatively inexpensive in an application like this and will be well worth it in terms of improved function.
Migration System (LED Lights) Redesign
- We acquired a plastic tool box from the surplus inventory to conduct a test to see how the BSFL react to light.
- To set up the test, we took some card board to separate the tool box into 3 separate sections, with small "door ways" so the BSFL could move from the middle section (starting point) either of the 2 side sections.
- For our first test, we placed the BSFL in the middle section, closed the lid so the inside of the bin was dark, and waited for 10 minutes.
- For our second test, we placed the BSFL in the middle section, placed the tool separator on top so light could get into the middle section, and waited for 10 minutes.
- The results from both tests showed that more flies moved to the side sections during the second test, meaning the larvae were more likely to move away from light.
- This shows that it could be useful for us to implement light as a way to encourage the larvae to move upwards when they're ready to pupate, rather than downwards. The larvae moving down rather than up has been a problem for teams in previous years, and our team has witnessed this during our current testing of 19422's prototype.
- The addition of lights into the system is an incurred cost that previous teams have not experienced. However, this cost will be well worth it if they can be utilized to invoke the desired response from the larvae.
- An additional cost of implementing lights into the system is the need for electricity for power and a micro-controller to operate the lights.
- In order to analyze the feasibility of ramps in the design, we utilized the previous team's composter and analyzed the behavior of the larvae
- Through our tests, we determined aspects of the ramp design that invoked desired behaviors from the larvae (ie. Corners, Impact of Light, etc.)
Computer Aided Model
- When testing, the larvae were climbing down and under the ramp.
- We realized this was because there was a lot of ambient light in the room, so we covered the ramp with a 2x4 to darken the ramp.
- We also noticed the larvae weren't climbing up the ramps because the ramps were dry. We then wet the ramps with some water.
- The moistened ramps in combination with the 2x4 covering seemed to do the trick. The larvae finally were climbing up the ramp.
- Our customer also informed us that the larvae like climbing up corners, so we decided to incorporate that into our prototype design.
- The new design for the ramp within the composter allows for egress along only one side, minimizing manufacturing costs (time and materials)
- As it is known that the larvae prefer climbing in corners, T-bar will be used to maximize number of paths and limit material costs
Adjustable Height Redesign
- Based on the estimated cost of the current structure, it would would not be feasible to implement variable height while staying below the desired price-point
- Rather than attempting to accommodate researchers of various heights through adjustability, we will work to accommodate the broadest range possible while maintaining reasonable hopper volume
- As discussed in Conclusions (above) the cost of implementing this system would be far too great to justify, as the composter can still be operated and function without it
Drawings, Schematics, Flow Charts, Simulations
Computer Aided Model
- The design features a single point of egress for the larvae and utilizes T-Bar to maximize corners, which the larvae prefer to crawl in
- The design will likely feature lights to invoke a response from the larvae, with the goal of motivating them to migrate up the ramp to a containment unit for pupation
- The removal system being pursued is the concept we referred to as a "revolving-door"
Bill of Material (BOM)
PurposeConfirm that all expenses and contingencies are afforded by the project financial allocation
Input and Source
- Design Files
- The most expensive parts of our prototype at the
- 80/20 for the frame.
- Plastic for the structure of the composter.
- Alternatives for the frame could be plywood or less expensive brands of extruded aluminum.
- Originally, Lexan was considered as the material to build our composter, but we looked into cheaper High Density Poly-Ethylene (HDPE) which cut costs by about 1/3rd.
- These alternatives will be explored more in the next phase.
Output and DestinationLink to the BOM can be found here.
- Formalized test procedures will be developed in future MSD phases
An excel file of the test plans can be fond using the following link: Test Plans.
Risk AssessmentThe following risks were identified in the Preliminary Detailed Design phase:
- Group member not contributing enough
- Not being able to get a manufacturing consultation
- Team member does not return for MSD 2
- Team members not agreeing on subsystems to use
- Not having enough time to meet outside of class as a group
- Not reaching all of our subsystem goals
- Materials ordered are not what we need
- Obtaining materials takes too long
- Composter does not fit in shed
- Material desired for construction costs more than desired
- Finding a material to use for the base of the composter takes too long
- A group member gets injured
- Team all become very sick
- Larvae not replicating results from testing in final product
Design Review MaterialsThe agenda for the preliminary detailed design review presentation can be downloaded using the following link: Agenda.
The preliminary detailed design review presentation can be downloaded using the following link: Presentation.