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Client Comments on Report

We received your report. Your observations about the difficult installation and potential failure of the thermocouple are interesting. What are your recommendations? Your finding that energy to produce the product dominates use is interesting. Does your calculation of 5.5 hours for freeze time match observation? Are there ways to reduce this time?

Detailed comments:

• Your description of production function is very clear. Does the fill really work on a timer? How does it compensate for different flow rates in the feed line? How are the circuits closed and opened? A picture or diagram would help.
  • Graphic of cam rotation has been aided, and follows with flow chart description.
• Any general findings from your BOM? Please include a picture or drawing of the assembly with parts of the BOM labeled. Where does the valve show up?
  • From our Bill of Materials we found that many of the parts are standard parts and sub-assemblies that were purchased. The parts that are specifically designed for this product were injection molded or cast. The assembly itself is fairly simple in design although there are interacting mechanical and electrical systems.
• In your DFE you mention that the motor runs for 15 minutes per cycle. Why does it run so long? Why do you not include the heating element? Also, how much additional energy must be provided by the refrigerator to continuously freeze new water entering the freezer?
  • The alloted time of 15 minutes was an approximation based on our perception of how the ice maker worked. We did some research and we found that the motor actually runs for about 30 seconds. The heating element was not included because we had not found information about how much energy it requires. We have acquired this information as well as the time per cycle (30 seconds) and have included it and the additional energy required for the refrigerator to freeze the new water entering the freezer.
• Your BOM lists the tray material as unknown, your DFMA reports that it is injection molded (thus with integrated plastic), and your analysis assumes aluminum. Which is it, and how do you know?
  • The tray is made of Teflon coated aluminum. We learned this from a meeting with Yoed Rabin, an faculty expert.
• Your DFA comments are pretty short. Were the DFA guidelines followed?
  • More information has been added after reviewing guidlines.
• Your analysis is very short, and there is not enough documentation for us to understand what you did. You mention simple analytical solutions - where are those? The shape shown in Figure 1 does not appear to match the tray shape. Is part of this shape water and part aluminum? Why does Figure 3 not show a flat spot at zero degrees during phase change?
• What are your FMEA findings and conclusions?
  • The most severe failure modes and recommendations have been added.

We look forward to seeing your market research and new ideas in the next report.

Client comments on the Mechanical Analysis

This well-performed mechanical analysis focuses on thermodynamics of ice maker, which is critical to its functionality. Here are few comments to the analysis:

• In your bill of material, the material of ice tray is listed as unknown metal, but this analysis seems to assume the material as aluminum without further explanation. Please check the consistency in your document.
  • The material was determined to be aluminum coated with teflon. The teflon coating is not accounted for in the simulation because it is relatively thin.
• Please list the thermal properties of water and aluminum you used in the FEA.
  • The thermal properties are taken from "Heat Transfer: J.P. Holman" as previously cited. Graphs of the values are now provided.
• Currently we can not tell how the boundary conditions and initial conditions are applied in your FEA model. Please indicate them clearly in Figure 1 by using textboxes.
  • The initial conditions and boundary conditions, as seen in the table, have remained the same. Labels and a better description have been added in order to clarify.
• It is worthy a note that converting 1 gram of ice at 0 °C into 1 gram of water at 0 °C requires additional 333 J of heat. Please make sure this is taken into account and added into your assumptions.
  • We have decided that a transient analysis is too expensive in preparation and computational time. Instead we decided to use the power drawn from the system as an objective value to compare other designs against. ANSYS allows us to compute the W/m^2. We can use this and the area of the model to compare alternative designs.
• Please give more conclusions upon your analysis results. For example, can the simulated 5.5 hours represent the practice freezing time? How do you apply the single-cube analysis results to the whole tray?
  • More detail is added to the conclusion.
  • Aluminum has a very high thermal conductivity and a very low thermal capacity. It is assumed that the resistance of the tray is minimal and that proximity of cubes is not as important as the cube shape and surface area.