Phase 5 Review
Team Vision Review (Overall and Week 15) and Engineering Requirements
Review of Final Phase Shared Vision
Review of Overall Shared Vision
Engineering Requirements Update
The customer and engineering requirements were determined at the start of MSD I, and slightly evolved into what they became at the end of MSD II. They were attempted to be met by the build, but some of the specifications were simply outside the realm of possibility at this time. The color coding for these were:
> red - not met
> yellow - conditionally met/not tested yet
> green - met unconditionally
Problem Tracking Update
Over the course of the semester, we have logged our issues. The issues were then to have ideas generated on how to solve them, along with an implementation plan. The solution was carried out, and then reflected upon to see what went well and what more needed to be done.
The most important additions as of late regarded the acme screw and its issues at the supplier, that the acme screw pillow block assembly did not line up perfectly at the base.
Finalized Bill of Materials and Budget Summary
The parts needed to build this system were organized in an excel sheet. The sheet shows design specs and cost for each part. It also prices out what each paying department would spend, based on our agreement with them. The parts were color coded throughout the process, with the following:
> red - not being ordered yet
> yellow - in transit
> green - currently in house
> blue - shipping costs
Fabrication of parts to be machined in house began after the final design was approved during the Week 5 design review. The final design saw the removal of the sliding gearbox is favor of a simpler plate design that would greatly reduce fabrication time and reduce the number of parts required to machine. This decision also helped with the weight reduction aspect of the design.
Both halves of the mover were built in tandem to minimize the changing of tooling and need to have shop personnel assist with operations such as aligning, milling, and welding. Fabrication began with the base frame, which required the alignment and welding of the wide cross-brace to the narrower tubes, creating an "H" shape. Once the frames were welded, rectangular plates for the wheels were drilled and tapped. They were then welded to the frame in such a way that the frame was lowered in order to create a more advantageous center of gravity that is closer to the ground. This reduces the risk of tipping when loaded with a table.
The uprights were machined next. There were four uprights altogether, each consisting of two tubes and a plate to keep the tubes parallel to each other. After welding the plate to the tubes, all four uprights were milled to ensure that the heights were identical. This was done to ensure that the upright caps will lay flat and allow us to properly align the acme screw during assembly. This also allows for easier welding of the uprights to the frame.
Both of the sliding plates were machined to be identical, although there was a bit of extra work required due to a lack of material. A surplus steel piece was welded to the piece intended to be used and smoothed so as to operate properly. This has proven to be a cost-effective decision that does not effect operation. The rotational bearing piece is bolted to this sliding plate along with the screw block that contains the acme nut. This screw block acts as the interface between the acme screw and the sliding plate and is the backbone to the motion of the sliding plate.
The jaws and back plate are the key to the rotation system and an important part of lifting as well. There are four jaws total, two top jaws and two bottom jaws. The top jaws consist of one plate that has two simple holes for connection to the back plate, and another plate with slots cut out via the FlowJet machine to allow for 1/4-20 screws for interfacing with the table during lifting. These plates are welded at a right angle and supported by three triangular ribs evenly spaced across the jaw. Each of the bottom jaws follow the same method but do not contain the slot pattern seen on the top jaws.
The backplate will be modified as needed to allow for different attachments and different modifications in order to accommodate lifting objects other than the vibration isolation tables. The shop has determined that they will modify the back plates as needed. Should the current back plate be welded to the rotational shaft, a new assembly may need to be built for uses other than lifting the specified tables.
The remainder of the parts were assembled and installed based on the alignment of the acme screw. The acme screw was aligned to be in the center of each frame. Once this was done, the upright caps could be welded/screwed into place, locking all components of the lifting and rotating system into place aside from the jaws and back plate. The brake pedals were also fastened at this time by two square tubes connecting to the brake and the cross-brace of the frame.
Final Technical Paper
Action Items and Status from Final Project Progress Review
- Finish Testing and Update Documentation
- Inquire about getting paint from the Hockey Team to Paint Project
Team Self Critique/Postmortem and Gate Review Information
Conclusions and RecommendationsWe have completed construction of both units and have begun to complete the remainder of the test plans. While we have produced the device to our customers, they have agreed to let us continue testing in order to ensure our theoretical calculations and design assumptions. We have conveyed our interactions involving our customer's requirements illustrated in the PRP document as well as their specific engineering requirements. All final documentation not represented in this phase will be presented during the Gate review.
Each member of the team had a hands-on experience with implementing the engineering process. From identifying the problem of a customer to implementing an effective solution. We also developed an understanding of how to work in a team with other engineers (potentially of different backgrounds) Furthermore, we developed proper hardware sizing and selection for components such as bearings and lead screws. Many real world applications require an engineer to have physically used and understand many components that are not reference in the classroom. It is very difficult for a developing engineer to understand the true characteristics of certain design components until they have physically held them. Finally, three of the four members of the team gained great experience in proper machining techniques and metalworking. As described above, many design changes were altered for the benefit of build progress because a machining technique that was not previously acknowledged. Many developing engineers such as team P15741 have learned that in some instances, design problems can be resolved through manufacturing techniques such as replacing specific fasteners with welds.
Our team has made some future recommendations should this prototype unit be revisited for design purposes. These recommendations are made as suggestions to our customers or future potential MSD teams that wish to improve upon the current design.
- Our team has left room within our design to allow our customers to create different fixtures of variable shapes to perform additional tasks. By simply matching the proper bolt hole patterns, and new function head may be created.
- Total system weight can be reduced as this prototype was over designed to sustain maximum possible loads. Future improvements can include a manufacturing model of our prototype.
- Our customers have opted to implement their own handles and supplementary attachments. Future designers may optimize these components.
- While our finished design was over designed for the transport of isolation tables, it should be noted that testing parameters should never be placed beyond that of an isolation table.
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