Talk:Umbrella

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Client Comments on Report

We received your report. Your most important findings seem to be that 1) the umbrella is already well optimized for DFMA, including the use of symmetry to reduce unique part count, 2) usability factors hold the most potential for improvement, and 3) that the top failure modes include canopy tearing and arm failure (which matches our data). You found that a 10 pound compressive axial load will buckle the current arm. Is compressive axial loading to cause buckling the primary mode of failure for these arms, rather than, for example, bending?

Detailed comments follow:

  • You mention the issue of nonuniform coverage; however, users often tip the umbrella rather than hold it perfectly vertical. How would this affect coverage and the drip pattern.
    • While tipping the umbrella does change the coverage pattern, this effect is small in the side to side dimension. The primary problem with non-uniform coverage, is that the umbrella is often held to one side of a user, resulting in decrease coverage on one side. Since a user is longer from side to side, than from front to back, the minor offset caused by holding the umbrella in front of the user is negligible compared to the side by side offset. In regards to the drip pattern, most umbrellas are designed such that the drip pattern in any direction does not have a severe impact on the user. The only case in which the drip pattern would be seriously considered is in the case where two people are walking side by side.
  • Please include an assembly drawing with parts labeled to contextualize your parts list. Also, you did not include any text to describe the parts list. Were there any findings?
    • An updated assembly drawing can be found in our updated parts list section.
    • The significant findings from the part breakdown were listed in the DFA and DFM sections of the report.
  • Your list of stakeholder needs looks quite good, but you didn't include any text to introduce it. Are there any major trends or findings?
    • At the time of writing the first report, we had yet to uncover any significant trends or findings. We did further investigation into our stakeholder needs for our second report, and were able to determine 4 major categories that warranted design studies. Further analysis of our findings can be found in the relevant report.
  • You mention that there is much variability in attaching the handle to the shaft. Does this create problems in causing visual variation in a bin full of "identical" umbrellas that would communicate low quality to consumers and hurt sales?
    • The umbrellas were all hung from the handle in the store display, so umbrella height difference would not be noticed by the customer unless he or she kneeled down to inspect the bottoms. From the user research, we did not notice durability to be as significant of a concern as usability and availability. In addition to this, variability in the way umbrellas are stacked in bins automatically lends itself to height variation (leaning, etc.) mitigating the effects caused by shaft length variation.
  • You mention that the fasteners do not need to be manufactured - do you mean that they are purchased from suppliers where they are manufactured at large economies of scale?
    • Yes, standardized fasteners would be purchased in large quantity from a supplier. The DFM section has been updated to reflect this.
  • Nice job in breaking down the product into categories for your LCA; however, wholesale trade would not capture assembly costs - only trade. You may reconsider your breakdown.
    • We reconsidered our LCA breakdown, but were unable to find any EIOLCA catagory that was able to accurately describe assembly costs. Given the inherently general and approximate nature of EIOLCA, we believe that our current breakdown is sufficient for our Life Cycle Analysis.
  • What scale was used for your FMEA assessments?
    • The scale used for our FMEA assessment was taken directly from our textbook, Engineering Design by Dieter and Schmidt.
  • Your mechanical analysis is quite good, but is buckling under axial loading the most likely mechanism of failure? What role would shear flow play, given that this is an open channel design? You mention the possibility of a closed-channel design - would such a design still function in folding up, and would it strengthen the arms significantly?
    • The arm support shaft is connected by a pin joint at both ends. Because the rider (part 17) and hub (part 13) cannot rotate relative to the shaft, the only load on the support shaft would be axial. Shear flow differences between open and closed channels are mainly an issue in bending, not in axial compression, and we do not anticipate it to be a significant factor due to the end restraint conditions on the member.
  • Your documentation of alternative umbrella designs is excellent, but we had difficulty understanding the description of the auto-open-close design from your text. Maybe a picture or diagram with labeled components would help to clarify.
    • An updated picture of the auto-open/close mechanism has been uploaded to the auto-open/close section of the report. This updated image should facilitate in the understanding of the mechanism.
  • Please comment on your design process.
    • Comments on our design process can now be located in our design process section of our updated report.

We are looking forward to seeing your research findings and ideas in the next report.

Client comments on the Mechanical Analysis

It is a well-written mechanical analysis, which focuses on the U-shape linkage, a critical component in umbrella design. The analysis includes both analytical calculation and finite element simulation for the buckling with well described assumptions.

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