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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:

1. 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?
2. 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, or toasting crumbly bread)?
3. 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.
4. Please include a picture of the assembly with parts labeled to help interpret the bill of materials.
5. Why was aluminum chosen for part #2 if other parts are steel?
6. 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?
7. 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?
8. 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).
9. 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?

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.

Discussion of Presentation on Wednesday, September 24, 2008:

 12:38:44 PM : Do you think that the power consumption curve is linear over the duration of the cycle? That is, does the wire resistance change as the coils heat up?

 1:19:17 PM: It was a little unclear sitting towards the back of the room looking at your pictures, but how easy are the "tabs" to manipulate if you are a plant worker assembly many of these toasters every day?

 2:46:58 PM: You went over the manufacture of the metal casing and most of the interior structure, but how is the mica insulating plate made? 

 4:55:44 PM: If the most likely failure is in the handle, did you notice any design features that were incorporated to account for it?

 8:00:49 PM: Overall, I thought your presentation went pretty well, but I do think you shouldn't have gone as far into detail about how the toaster works as you did.  Maybe it was necessary to explain some of the things you wanted to talk about, but it seemed to take up a lot of time and didn't really help me much.

 9:05:28 PM: In class, you responded to my question about the timer, saying that on a cold day, the toaster, if adjusted for hte first piece of toast coming out properly, will cause the second to come out underdone. Would it be possible perhaps to add a preheat cycle to the toaster for just a matter of seconds? And from then on have the timer work correctly for a given darkness of toast?

 9:39:28 PM: I remember when I was little, we had this really old toaster that wouldnt go up all the way when it was done.  Instead it would get caught half-way up and would continue to toast.  I was toasting bread once, forgot about it, and next thing I noticed the toaster caught fire.  Long story short, I freaked out, but I thought this story may be a bit of interest to you.

 11:36:45 PM: Have you guys thought about modifying the lifting (?) mechanism (the structure that pops out the toast when it is cooked) so that the user can stop the toaster and take the toast whenever he/she wants?

 8:17:00 AM: I thought the pictures were good, the presentation I felt went in a little too much detail. I rather have heard less detail and more content on the big picture.

 9:27:00 AM: Do all toasters typically use a nichrome wire element mounted to mica, or are there toasters that use heavier elements as well?