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Revision as of 23:47, 12 October 2008

Client Response to Report 1

We received your report. From your summary, it seems that the most important finding is the opportunity to reduce part count to reduce complexity and assembly costs. Do you have specific ideas about which parts could be eliminated? Were there any other major findings or recommendations?

Specific comments follow:

• Your description of the toaster function is interesting, but it is difficult to see all the details from the pictures you provided. Where does the handle interact with the switch mechanism? How are the circuits completed? What triggers the capacitor to discharge once its maximum voltage is reached?
  • Akshay
• Nice pictures in the user study. Are there any non-ideal use scenarios you did not consider (such as thick slices getting jammed, toasting bread that is too short, toasting crumbly bread, or loose pieces falling against the coils and burning)?
  • We addressed the mechanical failure modes in our FMEA analysis. As far as non-ideal use scenarios go, these were addressed in Report 2 of this project. There we surveyed users in order to identify design problems and non-ideal uses associated with toaster use.
• Your stakeholder and user needs list seems incomplete. Please consider special users, like children, and examine additional important needs such as safety, ease of cleaning, adjustability, and ability to know what setting to use to obtain desired outcomes. Finally, please compile your list of needs into a bullet list.
  • Leigh
• Please include a picture of the assembly with parts labeled to help interpret the bill of materials.
  • Akshay
• Why was aluminum chosen for part #2 if other parts are steel?
  • Jon
• Your DFM describes how parts were made, but do you have any conclusions about whether good DFM practices were followed? Your DFA observations about tabs for quick assembly without fasteners is interesting. Were other DFA practices followed well - e.g.: does all assembly take place from the same direction onto a base without obstruction where possible? It seems that it would be difficult to thread the bread shelves through the holes in the plates and secure them. What is the most difficult step?
  • Leigh
• Your FMEA identifies fatigue as a failure mode. Is this from cyclic mechanical loading or thermal loading? Why did you assume a four year lifespan? What scale was used for your FMEA table?
  • Jon
• Your DFE analysis is insightful, and the sectors you found seem representative. It looks like the dominance of the use phase will depend on frequency of use. How did you come upon the numbers you used? Also, you seem to have a mismatch in total GHGs from power generation and supply (you are considering only primary emissions and ignoring those from, for example, mining).
  • Ian
• Why did you choose the question you did for the mechanical analysis? Isn't it obvious ahead of time that the shelf will not yield to the force of the weight of a slice of bread? What is the worst case force the shelf would encounter? What assumptions were made in your model? You provide only FEA pictures, but we cannot tell what assumptions were made on boundary conditions and why these are representative of the scenario. Why is this analysis useful - what do you conclude?
  • Jon
• Please comment on your process.
  • Ian

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

Client Comments on the Mechanical Analysis

In this report, the toast shelf is selected as the major component for an finite element stress analysis. The report pointed out that the failed toast shelf would make the toaster become a potentially dangerous appliance. However, I would like to see more explanations about why the toast shelf failure can cause such serious a problem because it is not included in your FMEA.

As a client, I would like to see more professional details in your analysis. The following information should be included:

• The finite element software and version you used for the analysis.
• The material property settings: for example, the values of tensile strength, Young’s modulus and poisson’s ratio.
• Please describe more about your boundary condition settings.
• The maximum applied force to cause the toast shelf failed.
• Plus, if the toast shelf material is aluminum, you may want to consider the offset effect on elastic limits if necessary.
• The report indicated that the long recess helps improve lateral stiffness. In order to demonstrate the difference, please provide the analysis results for the similar design without the recess.