Talk:Doughnut maker

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Revision as of 17:21, 29 September 2009

We received your report, and we have some comments and questions. It seems that the existing product is particularly a disaster from a usability and failure perspective and that these are the most obvious areas for improvement. We also are glad to see potential in DFMA and energy use as well. Please respond point by point to the items below. We are looking forward to seeing your ideas in Report 2.

• Executive Summary: Thank you for the clear summary. Please watch typos.
• Stakeholder Needs: Thank you for the list, but please comment on the most interesting or critical findings. We noticed that you didn’t list noise or vibration as a need.
• Use: Excellent detail of use, and very useful observations of issues ranging from difficulty monitoring oil level to difficulty cleaning. Could you compile the major issues into a bullet list? Please provide some type of flow chart to help interpret all of the text. Some questions:
  • Did you try only 1 of the recipes – might the device work better with the others?
  • What is the cause of variance in degree of undercooked output?
  • The difficulty filling the dispenser is not fully clear from the text.
  • You mention that the machine produces one doughnut per minute but later say 20 per hour. Which is it?
• Assembly: Thank you for the clear pictures.
• Mechanical Function:
  • Please explain the circuit diagram. Some of the symbols are nonstandard and not clear. For example, why are there multiple lines from Conveyer to V-, what trips the switch on the top right of the diagram, what are the empty box symbols, etc?
  • Should the target oil temperature be adjustable by the user? It sounds like the temperature controller is a bang-bang controller – please comment.
  • Please clarify how switch 2 maintains the circuit until switch 1 is pressed. Are they both on the same component?
• Mechanical Analysis:
  • At what temperature will the outside of the donut "crisp"?
  • At what temperature will the oil smoke and/or burn?
  • Did you leave some safety buffer between the maximum oil temperature you allowed and these problematic temperatures?
  • Which will happen first at high temperatures: crisped donuts, burned oil, or damage to the plastic parts?
  • You list some suggested cooking temperatures and times, but how did you use that information?
  • What temperature does the oil reach currently, and how much more energy will the heating element require to maintain the oil at the higher temperature you suggest, rather than at the current temperature? Assuming the same heat input in both cases cannot be correct.
  • How much time does the dough need to spend at 160 deg F in order to be fully cooked?
  • How does changing the time step change your SolidWorks Thermal FEA results?
  • How long does your redesigned unit take to finish the batch of 60 donuts?
  • Does the redesign that you suggest pose any additional safety risks or cause any changes in failure modes compared to the current design?
  • Please define all of the symbols used in your notation and be consistent, especially with subscripts.
• Bill of Materials: Thank you for the thourough list. Why do you list several parts under the same part number (e.g. 028 and 036)? Also, please indicate any assemblies with the word “assembly” to avoid confusion (e.g.: conveyer belt).
• DFMA: Good comments on choice of manufacturing process, but do you also have any comments about DFMA guidelines? What does “a more idiot-proof design” mean – can you be more specific?
• FMEA: Good identification of major failures (there seem to be many). Should the dough dispenser motor speed be adjustable by the user? We’re surprised it wasn’t designed to be adjustable.
• DFE: The distinction between material flow as direct and gaseous emissions as indirect is not clear - indirect typically refers to up-stream supply chain emissions, while direct refers to the processes being examined directly (such as assembly or use of the product). You mention that metal parts are “designed to be removed” – please comment. It is not clear in your analysis where you calculated use-phase emissions or estimated CO2 tax implications. It appears that you only identified carbon emissions from electricity production used in manufacturing. Use "energy intensive" rather than "energy intense".
• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.