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Client Comments on Report

We received your report. Your general conclusions could use some clarity. What do you mean "The functions and manufacturing techniques involved in production of the parts themselves."? You mention that there are several signs of good DFMA choices, but what are they? Just the choice of stamping? What do you mean you "came across astonishing numbers" in your DFE? You mention that the gas tank, mower blade, and drive belt have concerns, but what are they, and what are your recommendations?

Detailed comments:

• Good list of stakeholder needs, but you seem to be missing some important ones, such as cost of purchase, cost of use, cleaning, maintenance, and durability
  • Included more stakeholder needs including the ones listed above
  • Discussed the possible clashing of some stakeholders
• Nice description of use. Please also include descriptions of function - how do the mechanisms work? Pictures would be a big help in understanding the mechanism. The assembly drawings are helpful but not sufficient to understand the mechanism without seeing the product. Please expand and explain.
  • Added more explanations to the parts list.
• Why are the front and rear wheels different?
  • Added parts list text an explanation. They actually aren't different. One is the same as the other with a gear assembled on it.
• In your BOM, please clearly identify any sub assemblies. You currently have them mixed in with components.
• What prevents the v-belt from falling off the pulley when the drive is released and the belt is slacked? Is the belt constantly in a slip and wear condition?
  • Added to parts list section. Changed the part name, and the part description.
• Why are you asking us to cross-reference different labels on your assembly drawings with different numbers on your BOM? Please be consistent.
  • Relabeled and re uploaded files with parts labeled in accordance to the parts list.
• Nice description of manufacturing processes used, but does the design follow good DFM and DFA guidelines? Can you comment? You seem to focus on user assembly, which is good, but please include your findings about the factory assembly aspects - as you know, assembly processes are quite different at high volume.
  • Indicated processes that demonstrated good DFMA (followed DFMA guidelines)
  • Discussed parts that portrayed findings about the factory assembly aspects of the product
• Your LCA did not examine the use phase, including gasoline combustion or gasoline production and distribution.
  • Considering since our prototype deals with cars and transportation that we might re look at how our product effects the environment in the next report. From a LCA standpoint we thought we'd look at how our transportation hitch could be recycled.
• What are your FMEA findings and conclusions?
  • From the FMEA we can determine the most high risk means of failure of the lawnmower. These failures have an RPN of over 100 and include stretching of the cables, leaking of the gas tank, and the blade getting rusty or dull. Although none of these failures are catastrophic they are all significant and can lead to the lawnmower not working optimally. All of these failures are due to regular wear and tear that occur from using the mower.
• Your analysis has a few issues. Your free body diagram does not include all relevant forces (forces in the x and y directions do not sum to zero). Does your tension calculation match observation?
  • For the purpose of this analysis it should be noted that the reaction forces that oppose the weight and tension act about the driveshaft at point 'O'. The reaction forces do not affect the analysis as they act through the point where moments are summed and therefore are not included in the diagram.
• Why did you choose this part for analysis?
  • It seemed like an interesting analysis and something where there was room for improvement
• What method did you use to optimize your design?
  • After running the initial analysis, material was removed from the model in areas of low stress concentrations while maintaining a high factor of safety
• You mentioned that the 0.03 lbs. of saved material could be significant at large volumes - please justify. Are you assuming that scrap from the stamping operation will be sold for recycling? What production volumes are you assuming?
  • Yes we assume that the material is recycled. If we assume that 100,000 mowers are manufactured per year, this adds up to 30,000 pounds of steel. This is a significant amount to be recycled and would more than cover the costs of changing the stamping dies.

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

Client comments on the Mechanical Analysis

This mechanical analysis focuses on a bracket for the engagement of power transmission. It is indeed critical to the operation of the lawnmower machine. Here are few comments to the analysis:

• Please indicate which FEA software you used for the analysis and also provide the material property settings, e.g. tensile strength, Young’s modulus, etc.
  • Solidworks and CosmosWorks were used to construct and analyze the part. The yield stress is 89,980 psi, Young's modulus of 30,000,000, tensile strength of 88,580 psi
• The boundary conditions in the FEA are not well described. Please use textboxes in the picture to indicate your boundary condition settings. Please double check it.
  • The boundary conditions have be added to the article