System Design Review Agenda
- Follow up on action items from previous phase
- Team vision for Phase 2
- Update on ER's
- Functional Decomposition
- Concept Development
- Concept Selection
- Feasibility Analysis
- System Architecture and Proposal
- Designs and flowcharts
- Risk Plan
- Test Plan
- Project Plan Update
- Phase 3 schedule
- 3 week plans
Team Vision for System-Level Design PhaseWhat did we hope to achieve?:
- Complete the action items left over from phase 1.
- Create appropriately detailed semester-long project schedule, with estimated durations and owner assignments.
- Complete appropriate benchmarking to locate similar products and processes
- Flowing down from engineering requirements, create a functional decomposition that addresses each requirement.
- Brainstorm a large and varied number of concepts to perform those functions
- Construct several viable system-level concepts by combining functional concepts
- Perform an appropriate Pugh analysis to determine the best system concepts and improve them.
- Make a decision on overall system design.
- Construct a systems architecture which fully describes and communicates the system concept
- Achieve agreement on the above with stakeholders
- Identify risks with this concept and develop an action plan to address them
- Perform a preliminary feasibility analysis on the concept and the project more generally
- Create a plan to test our engineering requirements
- Understand the purchasing system, purchase and then own rods by the phase review
- Create a detailed plan for phase 3, on an individual basis
What did we actually achieve?:
- Items from phase 1 closed out
- Functional decomp created, concepts and alternatives generated, system level concepts created and pugh analysis performed
- System concept selected (Vertical Hopper and Agitator with Magazine backup)
- Risk plan developed to address risks identified with the concept and project
- Semester long project schedule created
- Draft test plan created, all ERs are testable
- Phase 3 schedule and 3 week plans created
What didn't we finish?:
- Rods have been ordered but are not in our possession yet
Updated Engineering RequirementsAfter phase 1 we updated the engineering requirements. The live document is here.
BenchmarkingBecause this is a clean-sheet design project, benchmarking was primarily used to assist with concept generation later in the phase by finding industrial precedent.
Morphological Chart and Concept Development
Feasibility: Prototyping, Analysis, SimulationListed here are some questions that we answered to help solidify the feasible of our concept:
- What is the maximum diameter rod that will fit into the mini-crucible in the Vader machine?
To answer this, calipers were used to measure the opening at the top of the micro-crucible. The smallest limiting dimension was measured because of the oddly shaped opening. Below is a diagram showing where the measurement was taken. The opening was measure to be 0.2750 inches wide. This will allow us to satisfy our engineering requirements of feeding 1/8" and 1/16" rods into the crucible.
- Prototype a vertical hopper. Is it feasible?
To test whether the vertical hopper concept was sound and wouldn't jam, we created a prototype using a 3D printed funnel, a 1" PVC pipe as the hopper, and a cell phone as the agitator. The mockup was mounted to a counter and 6" steel rods were placed inside and the agitator activated. A dremel was used to smooth the inside of the funnel and some lubrication was applied.
The first prototype failed, rods were jamming in the bottom of the funnel.
To determine whether this failed because of the particular design of the prototype or because the hopper concept was unsound, we decided to test again with different funnel angles.
To improve on our first prototype, we decided to test many different angles instead of just one. The funnels were 3D printed with 60, 50, 40, and 20 degree slopes. The dremel left the inside surface of our first prototype very rough, so we decided to leave the surface untouched. We also created a custom agitator which vibrated more violently than the phone used in our first prototype.
This setup proved to be very successful. The more shallow angles also worked much better than the 60 and 50 degree funnels. The rods were able to drop out of the funnel consecutively without gaps between them.
We also tested rods of two different finish qualities. One had rough cut ends with sharp points and burrs, the other had smoother ends with all burrs removed. The smooth rods flowed out of the funnel very quickly. The rough rods flowed out considerably slower than the smooth rods, however it still functioned adequately. The funnel jammed if the ends of the rod were bent or severely misshapen. The results of time trials are shown below.
- What are the power/voltage requirements for the feeder?
The power/voltage requirements for our design can be accomplished by two ways; either using the power supply from the Vader systems itself or using an external DC voltage supply. Below is a diagram of what the circuit would be if the power was taken straight from the Vader using two DC/DC converters to step down the voltage from 200V to 3.3V to power the MSP430 and the sensors required for the design. This solution is not financially practical due to the prices for both the VI-263-CV and the NDY2403C. The price for the VI-263-CV 200V/24V DC/DC converter is $240.64 and the price for the 24V/3.3V DC/DC converter is $15.91. This solution is impractical due to the financial constraints when compared to an external DC power supply that can be obtained by the RIT Electrical Engineering Department for free.
- What is the largest volume that the feeder can fill inside of the Vader enclosure?
Originally the 1x1x3' size constraint was meant as a place rough estimate place holder. This feasibility analysis is meant to solidify a size constraint. The volume inside of the Vader machine and above the print head was measured. It was determined that a rod feeder should fit comfortably inside a volume 2' wide, 1.5' deep, and 3' tall.
- Can a magazine hold long slender rods?
With parameters for rod types specified for the design (12” long and 1/8” and 1/16” in diameter), research into industrial uses for magazines with metal rods was conducted to determine if this was feasible. The Ranger 112, FMB Micromag, and Tryton 112 (shown in order from left to right) are magazine designs used for storing and feeding metal rods. All three magazines hold rods with diameters less than 1/16” and hold bars that are longer than 12” (up to 2 meters). The Ranger 112 is a scroll-fed magazine while the Tryton 112 is a barrel loading magazine. With precedent in industry, it is feasible for our design of a magazine to hold the rod types we intend to use.
- What are the torque requirements associated with the feeder?
As several of our designs use a motor to hold the rods in a hopper, we wanted to know about how much torque a motor would need to output to hold the rods in a resting position. For this worst case scenario all the force from the weight of steel rods was placed at a 90 degree angle of the arm. A factor 3.0 factor of safety was used to ensure the speced motor will not be over loaded. With the number of rods shown in the table below, and a 1" arm .29 Nm of torque would be needed. This is reasonably achievable, for example many common drills can output well over ~40 Nm of torque.
- More detailed breakdown of our budget.
|Rod stock for testing||$150|
|Microcontroller & Electronics||$350|
|Housing & Attachments||$700|
|Prototyping & Disposable parts||$200|
|Imagine RIT & Display||$100|
|Risk & Breakage||$375 (25% of above)|
Systems ArchitectureThe proposed design is that of a vertical hopper with an agitator supplying rods into a set of feed rollers similar to a welding wire feeder. The system is controlled by a microcontroller (MSP 430). A proximity sensor checks the level of the hopper, a photogate determines when the agitator should be active, and a logic loop detects jams. A vibration isolator prevents the agitator from impacting the Vader and a drop catch at the bottom of the feed tube maintains constant control of the rods.
Risk AssessmentThe risk assessment was reviewed and edited; a mitigation plan for each risk was drafted and is shown in the image below. The live document for Risk Assessment can be found here:Risk Assessment
The team is concurrently designing a magazine based storage alternative as part of a risk mitigation plan, in case the hopper fails further testing.
Preliminary Test Plan
Below shows our first cut at creating plans to test each of our engineering requirements. This is a draft, to make sure we that we can envision how each can be tested, and detail will be added as we get closer to MSD 2. The live document can be found here: Test Plan
Plans for next phaseTeam Vision for Phase 3:
At the end of phase 3 the team hopes to have fully designed the highest risk subsystem of the device, with first cut designs of all other subsystems, and draft design output created. We want to have performed further feasibility study and prototyping to confirm that our proposed design will definitely be able to fulfill the requirements, or, failing that, to have successfully pivoted to our back up plan. We want to have spoken with an expert in vibrations engineering and from that meeting have a solution for vibration isolation in place. We will have a detailed project schedule for the rest of the MSD 1 course and a partial draft schedule in place for MSD 2.
Updated Phase 3 Plan:
Three Week Plans:
James Boyers: Here.
Mark Brown: Here.
Connor Connaughton: Here.
Mathias Mereles: Here.
Josh Hilton: Here.
Ryan Hollender: Here.