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Team Vision for Preliminary Detailed Design Phase
The team’s goal for this phase was to determine what the previous group left in the locker for parts as well as any design changes we wanted to make. We wanted to get a head start on building with last year’s parts to see what was missing. We also wanted to test the current hydraulic system for proper function and flow. The team planned to determine a bill of materials which will help create a budget down the road.
The team accomplished:
- Inventory/tear down of last year’s design
- Further refinement of design
- Developing a preliminary bill of materials
- Established testing procedures for the hydraulics
- Started to fabricate (weld) the base and other components
- Tested a type of metal spray paint for esthetic purposes
- Started to modify parts in the machine shop
Prototyping, Engineering Analysis, Simulation
A main focus of the team during the primarily detailed design phase is to come to understanding of what the previous team's designs were and what aspects of their design need to changed in order to create a working prototype/final product that accomplishes our team goals for the project. In terms of the feasibility analysis that was conducted during this phase, the focus of the team has been in the prototyping, opposed to engineering analysis and simulation. The following section will breakdown the assumptions, the current status of the prototype assembly, the results of the meeting with a Subject Matter Expert, and the results of testing of the hydraulic system. In the following sections, changes that we will need to implement when we move in the the Detailed Design Phase will be address, as well as some possible solutions.
Feasibility: Prototyping, Analysis, Simulation
Prototyping:
The teams first steps taken before starting to assemble last years design were to understand how all the different aspects of last year's design work together, to understand what fabricating and machining the previous team conducted, and determine if all the necessary materials are available to complete the full assembly of last years project design based on the CAD model and the part blueprints. However, initially, we as a team, made several assumptions that turned out to be incorrect regarding last years design, and they are listed below:
- All materials needed to complete the assembly were purchased and are available to us
- The hydraulics system was functional, however some leakage and some sticking is present
- The stock that was machined, is sized correctly according to CAD blueprints
These assumptions that were made during the previous phases were discovered to be incorrect. It is important to acknowledge that even though our assumptions turned out to be incorrect, it is important for us to discover these misinterpretations that we have regarding last years design team now, instead of not completing this prototyping until later and then realizing how the design is not feasible. The inaccuracies and methods in which they were proven to be false will be discussed later in this section.
Furthermore, as a result of these assumptions, the anticipated time to assemble last years prototype on the schedule was underestimated at 5 hours, and has become more of a 25 hour process.
Missing Seat Plate
One of the biggest assumptions we made in the beginning of the semester was that all the materials that they were working with last year, were saved for our team for the continuation project. However, during the Covid-19 shutdown and subsequent shuffle in August, the seat plate, that is a fundamental aspect piece of our design was lost. A large search ensured, with the help of Art, but the seat plate never turned up. While this piece is important, the team realized that the by having to create a new seat plate in order to replicate last year design, we are able to test out a new material and we are able adjust the seat design, if adjustments need to be made to create a working prototype.
A new material was purchased for the seat plate, aluminum, a lighter material, but would provide similar strength that the previous team was looking to achieve by utilizing steel. The team decide after some testing (standing on the plate in the warehouse) that the aluminum plate selected would be able to support the weight of the user sitting on the device. Additionally, since in the previous years design there is framing under the plate that prevents bending, the aluminum would not be subjected to bending upon the loading of the user onto the device, which was a fear the team initially had when switching to the aluminum plate.
Incorrectly Machined Parts
Another very apparent issue that was present with some of the previous team's fabricated parts is that, the tolerance of the parts prevented the assembly of some aspects of the design. For example, in some of the machined parts from last year, they created holes in which a rod is supposed to go through, however, since the parts have the same diameters and they both have some tolerance associated with them, the interference is too great to shove the parts together. The team now has to go back in and slightly widen all these holes, since last year's team did not check or account for this when machining the parts last year. See the image below for an example of the incorrectly machined parts.
Figure 1: Bottom Hydraulic Mount with rod unable to fit through the hole it was Designed to Fit through
Another thing that surprised the team, was the vast number of parts that required to be welding. No one on the team has any welding experience, however, Jared's friend Cam, has been kind enough to have been offering his services to the team, and he and Jared have been going and doing the necessary welding that needs to be done to assemble the prototype. Some of the welded pieces that were done by Cam can be found in the Figure 2 below.
Figure 2: Examples of Some of the Welding Completed by Cam
Noticeable Issues with Last Years Design:
As the team continues to go through with some of the assembly of last year's design, there are some aspects that the team takes issue with and will be planning to change when moving on to our final design. The first aspect is the hydraulic system mounts. For the base of the hydraulics, the mounting system that is use is as shown in the figure below. The team disagrees with how the hydraulic is mounted. Mounting the hydraulics to a tube and not the flat surfaces is unnecessary and we believe it to be a left over aspect of when the team was going to have a tilting feature in their device.
Figure 3: Hydraulic Mount System as Design by P20011
The top mounting system of the hydraulic system is another aspect. We were unable to locate the top mounting brackets from the previous years team (20011), so the team is going to implement changes immediately to this aspect in order to create a working prototype. The team was able to find the 19011 project team's hydraulic systems mounts which which we were planning to now use as the top mounts of the prototype. These however, would require changes to the design of the seat plate, but since the plate has yet to be machined, we will be able to go and adjust the design of the seat plate to accommodate the new mounting system. This also brings up another issue, we are facing, the water jet that is used to machine the seat plate in the RIT Machine Shop has been down for the last several weeks and may not be repaired soon. The team may need to find an alternative way to machine the seat plate, or look at an outside research to move forward with the assembly process.
Subject Matter Expert Meeting- Hydraulics
For the hydraulic system, the team was unsure as a whole on the best way to test the hydraulic system that is a staple of the device. In order to talk through the process and come up the first steps we should take to go about testing the device, the team consulted with Timothy Landschoot, a mechanical engineering professor within the Kate Gleason College of Engineering here at RIT. Professor Landschoot was able to offer the team some needed guidance. His first suggestion, was to just put some water or air running through the device in order to find any leaks and to better understand what is going on inside of the device. Then he suggested to input water into one of the ports to see if the hydraulic is able to move freely in either direction, and also made known to us the resources available in the machine shop that may be able to help us conduct this kind of testing. He also stated, that he would be available to help us later on in the project if we have more questions for him.
Kaylie also contacted a professor that focuses on hydraulics within the Biomedical engineering department, however, they have not gotten back to us yet.
Hydraulics Testing
During this phase, based on the guidance of Professor Landschoot, the team has begun conducting the hydraulics testing for the device. Since only one of the hydraulics is fully assembled only one side of the hydraulic could be tested. The other corresponding hydraulic, has a broken segment, since this is weight bearing portion of the assembly, a new part will need to be machined, as seen in Figure 4 below. There is stock of the same material left over from last year, and the team will work too machine the new part within the next week or two.
Figure 4: Broken Segment in Hydraulic
The results of the testing of one hydraulic show that the previous teams design can work with some adjustments. The only visible leakage of the water occurred around the inlet/outlet valves of the device. No visible leakage was observed around the body of the hydraulic. However, issues uncover during the testing showed that a stopper would need to be added to the bottom section of the device. During the testing, when water was inserted into the bottom inlet of the hydraulics, the lifting piston raised with no issues. But when inserting water into the top component to lower the piston back down, since no there was no stopper in the bottom section of the device, the position inside the hydraulic chamber went to far down and become wedged while blocking the bottom inlet valve, preventing it for raising again. A stopper will need to be added to the top in order to prevent this blockage. Despite this issue, the teams believes that with the stopper inserted the hydraulics designed in the previous years will be feasible for use during our continuation project.
Material Coatings
In addition to the other feasibly testing that was occurring during this phase, the team tried to research materials or coating that can be used for the device. This need was driven from the left-over parts and materials from last year experiencing a lot of rust, in just a little over of 5 months in a storage locker. Since the prototype would be place into a bathroom and restroom, where the device would be coming into to contact with water or other fluids it's important to have a material/coating that will prevent or is resistant to rusting and is able to be cleaned with everyday typically disinfectant and sanitizing materials as well. On the recommendation of Jan Maneti, in the Machine Shop, the team purchased, Rust-oleum, an anti-rust coating, the can be used to coat the existing material, so need materials do not need to be purchased at this stage.
Kaylie is currently working on finding ways to test and get access bacteria samples, in order to test the microbial resistance and/or adhesion to the selected coating, and if the material is water resistance and able to be withstand normal disinfection and sanitization processes. One sample material was sprayed with the coating, to prepare for the testing as seen in the figure below.
Figure 5: Coating purchased to prevent rusting of the material and an example of a piece of the device with/without the coating
Drawings, Schematics, Flow Charts, Simulations
As stated, this phase we are reconstructing the prototype from MSD team 20011
Figure 6: MSD 20011 final CAD model of prototype
Figure 7: MSD 20011 Hydraulic Diagram
Bill of Material (BOM)
About the Document:
The Bill of Materials details all the part components intended to put our device/prototype together. This document keeps track and makes sure all expenses can be afforded with our 500$ budget. Given most of the material from last year is in our locket already, we will not need to request for a budget increase at this time. Our group focused on determining what we had and what we still need based on the last years design. We realized we needed to order and design a new seat plant along with a ceramic covering or paint. This document is a work in progress and will need to be updated each phase.
Given this information, it is anticipated that our team will not need to request a budget extension due to last years prototype still being in the locker. So far, we have spent 50$ which is well within our budget. Our plan is to continue piecing last years design together but make changes accordingly based on the CR’s and ER’s given to us.
Above is the current BOM with last years material below the back line. This document will be updated as we progress through the phases and determine what parts are still needed.
A live version of this document can be found here.
Test Plans
The main focus of testing in this phase is hydraulics testing. Since this project has been attempted multiple years in a row we think we may be able to reuse the hydraulic system from last year. Looking at last year's EDGE page it is hard to tell if they managed to actually test the hydraulics themselves. It seems as though most of the design was actually borrowed over from the year before (two years back from us). Since we don't know exactly how well functioning the system is we need to test the basics and then work up to the specifics.
Our first test is simply to check if it moves up and down as expected. We run water through the system and do manage to get the piston to go all the way up and all the way down. However, once the piston returns to the lowest position, it gets stuck. It seems as though the way it is currently designed, the lowest position actually has the piston end below the hole for the bottom inlet/outlet. This in turn blocks the hole, meaning that the water cannot reach the other side of the piston, and will not move it back up. This should be a pretty simple fix, requiring us to add something to the inside of the lift cylinder to stop the piston before it reaches that lowest point.
Once these modifications are done we can move on to more in depth testing of the hydraulics, namely leak testing. While some leakage is inevitable, it is best to keep it to a minimum. To test this we would need to run water through the system over a time and see how much water does leak out. From there we could use soapy water to pinpoint the location(s) of potential leaks by seeing where bubbles are left behind.
More testing will also need to be done, in particular testing for hygiene, safety, loading, and human testing of the overall device, but these will come in later phases of the project.
We would also like to utilize bacteria testing to see how common bathroom bacteria is likely to react to the system. Doing this will allow us to attempt to account for it through the use of coatings, or even just altering a recommended cleaning procedure. Kaylie has started looking into this and we will return to it once we hear back about labs.
Design and Flowcharts
The overarching structure of our design is unchanged from the previous phase.
Figure 9, System Architecture
Figure 10, Design Flowchart
Risk Assessment
The likelihood and severity of risks have decreased during assembly and functional analysis of the previous iterations prototype. Preliminary testing of the hydraulic piston revealed issues that were less severe than our anticipated risks
Figure 11, The most significant risks
The live document can be found here
Design Review Materials
- Pre-read
- Presentation
Plans for next phase
The next phase of this project is the Detailed Design phase. We will look in depth at last years prototype we reconstructed this phase and conduct testing to decide what is viable and what we need to change. We plan on running tests to help improve the hydraulic system from last semester and generate calculations. We will also be attempting to run materials testing on the steel and aluminum being used in the prototype for possible biomaterials issues. Our goal is to begin making decisions on our final design and look at how to incorporate all engineering and customer requirements into the prototype. We want to be well prepared heading into next semester.
Each team member has completed an individual 3-week plan of their individual goals for the next phase, they are attached below.