Overview of Status of Analysis, Design, Fabrication, Tests, etc.
Our project parameters have recently been simplified due to new Operating Room information: our system will no longer include z-axis (vertical) movement.
Additionally, our design is now able to utilize both sides for the OR bed, making for a more stable bridge design as opposed to a cantilever.
We have tested and agreed with Dr. Shtrahman on a tilting mechanism, meaning we've nearly finalized all designs.
Accomplishments from Previous Week
Demo prototypes to our sponsor, discussed pros and cons of each, and settled on the double rotisserie concept moving forward.
Came up with safety feature concept using a ratchet and pawl mechanism to act as a hard stop in the event the operator forgets to engage the brake.
Established a timetable for purchasing parts now that a final design has been attained.
Goals for Next Week (list names after each item). Use specific and measurable objectives.
Upon arrival of parts, begin manufacturing of Rotisserie tilt device - Everyone
Upon arrival of linear sliders, test their load abilities with a Safety Factor larger than 2 - Everyone
Comprise part order list for Rotisserie device - Alex
Revise and update Final Report Draft - Chase & Ramzi
Comprise part order list for linear sliders - Ramzi
Sponsor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Meeting with sponsor (2/4/2019)
Regarding the hard stop ratcheting mechanism: it could work, but would require two ratcheting mechanisms to restrict rotary motion in both directions. Test out a single direction to assess feasibility first. Additionally, it may be nice to add a redundant safety feature where a rod can be inserted through clearance holes in the gear and the microscope housing bracket.
Response: noted, we will test out the feasibility of one ratcheting mechanism as a hard stop. We aren't entirely sure on inserting a rod as an additional hard stop as that would require drilling several holes into the housing bracket. Appropriate spacing of the holes would be dependent on the desired resolution of rotation. Perhaps we may only need a single hole and we could rotate the ratcheting mechanism so the holes properly line up. We would have to look into this a bit more but are considering it since safety is crucial.
Keep the end of the double rotisserie closer to the microscope objective clean, try to avoid placing braking systems here to minimize operator reaching and the potential for interference with the patient.
Response: we have been keeping in mind that no hardware on the double rotisserie should extend further than the microscope objective. We will also be keeping the side of the double rotisserie free from any hardware that requires operator interaction such as braking mechanisms or other components to keep this side clean and smooth.
Keep assembly and portability in mind. How easy is it to mount and dismount the microscope from the double rotisserie, and subsequently mount the double rotisserie onto the crossbar?
Response: we agree that these are very important factors regarding the design. We are considering making the bridge structure and cross bar out of 80/20 aluminum. This allows for a very modular design and prefabricated fasteners are widely available. The casters we are planning on using should make portability fairly easy.
Instructor Comments from Last Meeting and Actions Taken to Address these Comments (indicate date of comments and if via email or in person)
Meeting with instructor (1/31/2019)
Bring up cranking mechanism for vertical translation to sponsor
Response: we brought up this concept to our sponsor and he liked this and the alternate pulley concept we also proposed. It also helps with the possibility of jamming the crossbar that our previous concept had. Per our sponsor, the first iteration is most likely not going to have this since it should be fairly straightforward to implement.
Look in the components room, there may be linear slides available.
Response: this is a great suggestion as it would save us time and money. We will be asking Chris Cassidy (or whoever can get us in there) for access so we can take a look.
Regarding the microscope "box housing": look into purchasing an aluminum (or some other material) extrusion, it's easier to purchase than to manufacture one ourselves. Look at McMaster, Misumi, or alternative vendors.
Response: we will look into the above vendors and others as well. Depending on the cost and lead time we may just bend our own sheet metal using the press brake in the design studio.
It would be wise to utilize readily available, and known parts. Doing so would allow our sponsor to easily construct a duplicate in the future of he needs to.
Response: We brought this up to our sponsor. He is not opposed to purchasing some less expensive components from ebay for a first iteration. He did however mention that it may be smart to purchase quality products from specialized vendors (specifically in reference to the linear sliders) since they are going to be used in the finalized design anyway. This would save us time as opposed to buying linear slides from ebay for a first iteration and subsequently purchasing the quality slides from a specialized vendor for the final iteration.
Regarding the cup holder for the isolation leg: large diameter poly-carbonate or PVC cylinders are not too difficult to find and would eliminate the need to roll sheet metal into a cylinder. It would most likely be a lot more economical.
Response: this is a good recommendation as these are readily available and would eliminate the need for us to reach out to a metal working shop off campus since UCSD does not have a metal rolling machine. However, one of our colleagues has this machine so we feel that it would be best to continue with the metal rolling option. In the case of a sudden lateral force the moment on this member would be large, so we feel that for the time being welding the metal cup holder would provide more rigidity and structural integrity. We will keep this recommendation in mind as a backup plan.
Talk to sponsor about budgeting.
Response: we unfortunately forgot to mention this to our sponsor during our last meeting, however he is aware that we are probably going to be over the originally specified budget since he claimed that was just a rough number used to fill out the paperwork and seems to very flexible regarding purchasing. We will still bring this up to him to ensure that we are all on the same page.
Comments from Other Students in the Class (indicate date of comments and if via email or in person)
None to report
Risks and Areas of Concern
A reliable method to test the vibration requirement. Our previous method utilized an accelerometer and two integrators to give us a position profile. However, the instructors concerns of signal saturation from the op-amps and the vulnerability to noise considering the very small scale we want to measure have caused us to reconsider.
We were considering a method using a laser pointer and an optical sensor, but we are unsure how to execute this. We need to consult with Steve Roberts if something like this is even feasible considering the scale and if so, how to go about properly implementing it.
Resources or Information Required but not Available
More bed specs.
Our sponsor reached out to the OR (Jacob's Medical Center Neuro Room) and there are several different models of beds used for the procedure relevant to our sponsor.
We're looking into OR bed standards to get a feel for the dimensions. Will confirm with sponsor.
Schedule
Now that we have sponsor approval our next major step is to start purchasing parts used for the final design. From here, we will begin to build starting next week. See "Budget" section for specific parts that will be purchased next week.
Budget (list amount spent and amount remaining)
Now that our prototype has been tested and sponsor approved, we plan to comprise a parts list to order on Monday, 2/11 that will consist of the parts for the linear slides, vibration isolation legs, and Rotisserie tilt device. This is make a very large dent in the budget, but currently our budget stands similar to last week:
Spent: $151.74
Remaining: $1448.26
Progress on Report and Webpage
The first draft of the Final Report is complete. We will await feedback and adjust accordingly. Some sections are a sparse and will be added to as the building process progresses.