Team Vision for Detailed Design Phase
|Phase 4 Team Vision|
What is our plan?
- Finalize the entire system design consisting of the heating, compression, controls, and structural subsystems.
- Create a design package that includes: component drawings, assembly drawings, BOM, action list, and documented feasibility work.
- Receive input from subject matter experts on the design of our system.
- Complete test plans.
- Complete the budgeting spreadsheet for the project.
- Update risk assessment.
- Create a plan for MSD II.
What have we completed?
- Finalized the compression, controls, and structural subsystems.
- Pivoted the design of the heating subsystem to a pre-filled mold used to make a laminate sheet. The sheet will then be used to form an end product (the proposed gutter) using a vacuum forming process. Vacuum forming can be tested in the Construct at RIT.
- Prototyped the structural subsystem with wood material in order to visualize the location and arrangement of other subsystems.
- Conducted preliminary plastic melting tests.
- Began ordering materials (car jack for compression).
- Finished preliminary BOM.
- Updated risk assessment.
- Electronic components approved by Professor Slack
- Created plan for MSD II
The team progress report to assess design aspect completion prior to the Detailed Design Review can be found here.
This progress report details what we plan to have accomplished by the Detailed Design Review, what has been accomplished so far, the tasks that remain to be completed, decisions we've made so far, and questions for our customer and guide.
Transfer Molding DesignOur current overall design consists of the 6 subsystems as defined below.
- Electronics (yellow) - Electrical components to control and display the system temperature
- Heating trough (red) - Heating elements to melt the plastic chips into form-able molten plastic.
- Plastic transition (light blue) - The elements separating the heating trough from the mold cavity
- Compression (dark gray) - Compression force exerting elements to direct the plastic into the mold cavity
- Frame (light gray) - Rigid rectangular prism frame constructed from square tubing
- Mold cavity (blue) - Accessibility for a mold cavity in the future
Design Revisions are where the previous design revisions of the system framing and component placement can be found.
Our reasoning for choosing specific parts for this design is summarized here.
Current Design System Architecture
The full system assembly drawing package for the current transfer heating design can be found here.
Current Gutter & Mold Design
The gutter design was modified after new information was learned from initial prototyping. The gutter no longer uses a clipping mechanism and instead will be connected with the holes on the gutter flange. Additionally, the gutter is now tapered at one end to ensure proper mating between gutter sections. Further prototyping is required to adjust for proper dimensions.
The initial mold design is as seen below. For this design, a gate and runner system are still required as well as an ejection pin system to remove the part after molding. Documented research on how to design a mold can be found here.
Prototyping, Engineering Analysis, Simulation
The most important aspect of the frame is to have the strength to withstand the expansion forces that the car jack will exert on the system. A secondary aspect is that the frame will be designed to support its own weight. The frame will be constructed out of strong 5.08 x 5.08 cm steel square tubing with a wall thickness of 0.3175 cm (2" x 2" x 1/8" nominal sq. tubing), unless stated otherwise.
The key structural elements to analyze in the frame are:
- Tensile stress in the vertical tubing
- Bending and deflection in the top horizontal tubing
- Shear forces in the heating trough support
The key assumptions made in the following calculations are:
- The frame will remain at room temperature, as the heating elements will be sufficiently insulated
- All vertical members carry an equal load from applicable forces
- Square tubing connections are rigidly welded or connected otherwise
- Square tubing has a uniform cross sectional area
- Reaction to jack compression force is exerted in the middle of the top horizontal tubing members
- The maximum rated force of the car jack is used throughout the calculations
Impact of Moment of Inertial on BendingHollow tubing with larger moments of inertia were initially considered when designing the frame. Large moments of inertial are the result of larger cross sectional areas, larger cross section heights along the bending axis, or both. A thick walled tube that is oriented vertically has the greatest potential to resist bending.
These pieces of tubing include the following and are compared here.
- 5.08 x 5.08 x 0.3175 cm wall thickness steel square tubing (2" x 2" x 1/8")
- 5.08 x 5.08 x 0.635 cm wall thickness steel square tubing (2" x 2" x 1/4")
- 10.16 x 5.08 x 0.635 cm wall thickness steel square tubing (4" x 2" x 1/4")
The calculations for frame strength can be found here. These calculations do not reflect the diagonal corner braces that are seen in the pictures. From the calculations, it can be seen that using these cross sections yields beam deflections on the top tubing supporting the car jack of 9.1 cm, 5.5cm, and 0.9cm, from smallest cross section to largest respectively.
Equipment WeightThe legs and wheels on the frame will need to support all the design components. The total weight from all the components is found to be 263 lbs, not accounting for electronics, plastic input, and misc. fasteners.
All the system components and their weights are noted here.
Frame Strength ConclusionsOther methods to reduce the beam deflection in the frame are to provide more support for the horizontal tubing members by using framing on the corners. Using a 13.5cm (5.3 in) piece of tubing with the ends cut at 45 degree angles and attached as seen in the Top Frame CAD Model, the length of tubing susceptible to bending is greatly reduced. Finally, using the same square tubing throughout the design makes purchasing and sourcing the material much easier as long bulk sections can be ordered cheaper per unit length.
Frame PrototypingTo get a sense of the scale and clearance spaces within the frame, a rectangular prism was constructed out of slightly smaller 3.81cm x 3.81cm (1.5"x1.5") wood pieces. This frame prototype is seen below.
Plastic Melting Testing
Preliminary plastic melting tests were done on a hot plate to represent the conductive heating from the resistors along with an 1/8th inch piece of aluminum to represent the walls of the heating chamber.
The hot plate was initially set to 275 degrees Celsius as this is the melting point of PET plastic and the lowest maximum temperature of the system. Plastic PET chips were added once the aluminum had heated up.
Based on visual observation, the plastic in contact with the surface of the aluminum melted very quickly (about 2 minutes), however the plastic that was not in direct contact took longer to melt (about 8 minutes). This could be due to the fact that the melted plastic did not conduct heat very well and therefore the plastic on top was not getting hot enough. It appears as if the melting plastic was insulting the rest of the plastic chips.
The melted plastic is clear and has similar viscous qualities to hot glue. It solidified quickly and was fairly strong after cooling.
An aluminum block with a cavity was introduced to analyze the behavior of small container of plastic. This simulated the conditions within the heating chamber as there will be only one source of heat.
This test showed that the plastic immediately in contact with the heated surface melted, but the plastic past this point was unaffected. The aluminum block did not conduct enough heat up the sides to melt the entire cavity worth of plastic.
The top of the chamber was heated with a heat gun to see if some radiation heating within the chamber would help increase the melting rate of the plastic. However this only melted the very top layer which in turn insulated the plastic in the middle.
Based on these findings, the final design needs to be rethought and updated to accommodate for the possibility of poor melting conditions within the melting chamber.
Proposed Compression Molding DesignThis design tries to accommodate the issues faced when performing the plastic melting testing. By decreasing the thickness of the desired output product and adding heating elements to both sides, there is a greater likelihood of even heat distribution through the thickness.
The new design is similar to original but with a new heating system. The structure has minor changes to accommodate the new melting chamber.
Schematics, Flow Charts, Simulations
Wiring Diagram & Programming Flowchart
All electrical components were approved by Professor Slack from the Electrical Engineering Program.
Bill of Material (BOM)
PurposeIn this BOM we evaluate currently hypothesized, studied and planned material costs. There are close to no services that we need employ thus we are using this as a budgeting platform. Overall we are certain that our current provided budget of $500 will be insufficient as estimated cost is already sitting at $850. We will be putting in a request for an increase that will allow us to purchase our materials and advance the project.
Currently the only service we will be purchasing is the delivery fee from Klein steel when we place our raw material order for them to deliver the purchase to us. The cost of this service is $25.
Our test plan for experimentally verifying the engineering requirements are broken up into the following categories:
- T1 - Observations not requiring tools
- T2 - Length measurements
- T3 - Weight measurements
- T4 - Temperature and heat testing
- T5 - Efficiency
- T6 - Compression testing
- T7 - Safety
- T8 - Chip input size testing
The working Test Plans can be found here.
These Test Plans were formulated from the Engineering Requirements, which can be found here.
The Test Procedures to describe the testing processes can be found here.
A working Risk Assessment file can be found here.
Through the processes of re-scoping the project, the importance of many risks have been lowered or completely eliminated. These risks include:
- R5 - Unable to fill the mold with the flowing melted plastic
- R7 - The manufacturing process creates inconsistent parts
- R10 - Manufacturing start up cost is too expensive for implementation in Nicaragua
- R12 - Unable to test our machine in conditions common in Nicaragua
- R25 - No one to work the bottle recycling business in Nicaragua
- R29 - Production rate of machine is too low to be economically viable in Nicaragua
- R30 - Gutters will not be able to be attached to homes
- R31 - Gutters will not be able to attach to themselves
Additional risks have been mitigated by placing the plastic chips directly in the steel mold. These risks include:
- R4 - The mold will be too complex to machine and/or have melted plastic flow in to
- R6 - The mold may deform or break during usage
An additional risk was added due to the results from the preliminary plastic testing.
- R32 - Improper heat distribution prevents the chips from fully melting
Design Review Materials
Plans for next phase
|Phase 5 Team Plan|
Lessons learned from original design and MSD I
- Material costs can be astronomical
- Not all requirements can be met when constrained
- We will not deliver into the final customer, rather open leeway for another project team to finalize the process
- Transfer molding is not an easy concept to implement at a low cost
- Consult exerts more frequently through the design phase
- Take concepts back to the experts for review
- Put more effort into researching and claiming resources early on in the process
- Communication lines are vital for effective team functionality
- Scheduling technical tasks is a team effort
- Do not assume properties of materials
- Test system as early and effectively as possible
Immediate development structure into the pivot system for MSD II:
- Plastic melting and heating
- We must achieve heating across all surface area of the plastic chips.
- There are a series of mechanical processes that the chips can undergo to heat up through friction forces.
- To achieve effective melting these concepts must be exploited.
- Our current process did not work due to a lack of understanding of these facts.
- It must be made out of weldable material, must understand material properties.
- the way that it undergoes forces must be supplemented by trusses to evade material deformation under forces.
- The carjack integration must attach and interact with the structure effectively to transfer the forces efficiently, to be shown in the drawings.
- Joints must be able to withstand forces without breaking or deteriorating.
- Approved system by Professor Slack
- Schematics and overall system seem to make sense, need to be finalized and approved by an industry expert.
- Soon to purchase components for build in MSD II
- Must learn soldering or find someone that knows how to solder to put the system together once the components are in house for assembly.
- Testing plan to be established on component requirements.
- Compression system
- Carjack installation onto the system must be evaluated.
- Crank set up to be finalized and installed into the system
- Integration of system components
- Integrating all subsystems will be highly considered through the development phases
- Managing design of subsystems for effective integration
What we hope to achieve in MSD II:
After undergoing our design phase in MSD I we have learned a great deal about the physical, economical and geographical requirements of our system. After our testing phase proved that the hypothesized plastic behavior actually does not work as expected we have shifted project scope. Our main goal for MSD II is to create a sheet of laminate PET plastic that will have the capabilities of undergoing vacuum forming. This will be useful as the plastic will have the ability to gain an assortment of shapes with low constraint levels allowing for massively increased flexibility of the system. We will be producing a raw material fit for production of different products.
In the case that we finalize this earlier than anticipated we will move into product design for the vacuum former, but this is not in the current project scope.
Individual Three-Week Plans
- Ignacio Martos - Phase Plan
- Pierce Scroggins - Scroggins Three-Week plan
- Kyle Appleman - Appleman Three-Week Plan
- Vikas Patel - Patel Three-Week Plan