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Client Comments on Report 1

We received your report, and we have some comments and questions. It sounds like the major opportunities you identified are simplification of the mechanism and consideration of outsourcing. We are surprised that you your FMEA conclusions report high reliability, since we observe these products to malfunction or break with regularity. 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 brief summary.
• Stakeholder Needs: It is not necessary to list generic and obvious needs like cost reduction for manufacturing. Please focus on post-production stakeholders and be more clear with needs - for example, what does it mean to have a need of "mounting"? It seems that you are missing a number of relevant needs such as security or resistance to vandalism, ability to identify when roll replacement is needed, frequency of maintenance, ease of installation (e.g.: powered vs. not powered), etc. Cleanliness also could refer to the machine itself as well as the propensity to propagate germs and viruses from user to user. The ability to remove graffiti would be important for the use environment.
  • Stakeholder section updated.

• Use: Nice explanation and pictures
  • Included pictures of the mounting template and mounting instructions
• Assembly: Nice clear labeled pictures
• Mechanical Function: The figures for the spring mechanism are helpful, but it appears that you did not describe overall how the dispenser mechanism works mechanically.
  • The overall dispenser mechanism is described in the section added "How the Dispenser Operates"
• Mechanical Analysis: Your mechanical analysis calculation of torque appears to be correct but very simple and not particularly insightful, and it is not clear how you use the torque to conclude that the force is appropriate for all users. Is this the force to initiate towel movement or the maximum force required over the cycle of one towel delivery? It seems that it would be feasible and more helpful to understand how the torque on the cylinder caused by the springs depends on the angular position of the cylinder. This may be more helpful in a redesign. We think you meant that the force is tangential, not perpendicular. Also, please include a complete free body diagram of the problem you are solving. (In this case you are solving for torque but your FBD does not include torque.)
• Bill of Materials: Good list. You can list standard purchased parts as "purchased"
• DFMA: It sounds like you are saying that the spindle housing has no function - how does the product work without it? Your DFMA analysis discusses how parts were made, but you do not discuss examples where the designers did or did not apply good DFMA guidelines - please comment on each.
  • Though the spindle housing has the function of protecting the spindle, it is already inside of another housing that provides adequate protection. We tested the product without the spindle housing and we observed that it performs with the same level of reliability and performance. For the full response please see DFMA Analysis > Design for Manufacture > Housings.
  • For the most part, designers applied the DFMA guidelines. For examples and the full response please see the newly created DFM Guidelines and DFA Guidelines sections at the end of the Design for Manufacture and Design for Assembly sections.
• FMEA: Your conclusion contradicts your earlier notes on failures in the comments on use. Which is it? Also, how robust is the device to variance in towels being pulled very hard or very soft or at an angle or with wet hands, etc?
  • FMEA section updated. With regards to wet hands, there seems to be no problem unless the user holds the towel for too long and rips the towel due to it being wet. As far as being pulled very soft, we noticed that as long as there is enough force to rotate the spindle, pulling soft almost always resulted in a good rotation as well leaving the next paper in the ready position. The hard pull is discussed in the FMEA section.

• DFE: When the roll is low but not empty on a given day, would the maintenance person tend to throw out the partially used roll in order to make a fresh roll available and avoid running out between scheduled maintenance? How much waste is this? Given your results on carbon emissions coming primarily from the paper towel production supply chain, paper towel waste associated with a dispenser sounds like the most critical aspect to study.
  • From our interviews with maintenance workers, some of them use the used roll for other cleaning purposes. Others leave them next to the paper towel dispenser in the bathroom they were in. In both cases it seems like they do not get wasted or thrown out, although it would be better if we could ensure that each roll was used in its entirety before it was thrown out.

• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.
  • First image cited in references. All other images were created ourselves.