From DDL Wiki

Client Comments on Report 1

We received your report, and we have some comments and questions. Your highlighted opportunities appear to be addressing failure modes? Several sections of the report appear to be duplicated. Please respond point by point to the items below. We are looking forward to seeing your ideas in Report 2.

• Executive Summary: How do you arrive at the $1.5 billion figure? According to your figures, if every household purchases a $40 feeder every year, this would be only $4.4 billion revenue. Somewhere between 30-70% of households have dogs or cats, but these households would not buy a new feeder every year.
  • The figure was produced as a compelling motivation for context. It is not intended to be a projection of revenue, but merely a value to approximate a saturated market to motivate entering it. It is true that anywhere between 30-70% of households have pet feeders. In this case, one could approximate that there might be a market valuation anywhere between $1.5 billion to $3 billion. To arrive at this figure, a number of assumptions are made. There are many other variables to consider that would affect this figure. They are; the number of animals in the house, the frequency a new feeder is purchased, the number of pets per feeder in households with more than one pet, etc. A conservative estimate was made to say that 30% of households have a need for a pet feeder annually given the myriad factors discussed above. The decision whether or not a person purchases a pet feeder is not a concern for this approximation as the motivation was to represent a saturated market where everyone who can buy a feeder, namely those individuals that have a pet and need to feed a pet, purchase a feeder.

• Stakeholder Needs: Good list of needs. Some appear to be missing such as quiet operation, low floorspace, easy to clean, etc.
  • Needs have been added

• Use: Clear description. What happens if the user forgets to twist or if they try to operate the machine with treats instead of dry food?
  • If the user forgets to twist the lid could easily fall off of the hopper in this case, the pet could knock the feeder on its side, causing food to spill onto the ground, and allowing the pet to consume this food at its own pace. Treats are not to be used because they are significantly larger than individual pellets of dog food. The size of the treats could cause a jam, as well as be difficult in regards to portioning the food.

• Assembly: Very clear

• Mechanical Function: Where is the timing belt mentioned in the description? Reference to part numbers will help. Are you certain the belt is a timing belt? Which component trips the limit switch to shut off the motor?
  • I intended to describe a belt/pulley system that utilized a timing system. The belt itself does not allow for accurate timing, but rather the plastic gear that is rotated by pulley/belt trips the limit switch. The gear has protrusions from it's face, which contact the limit switch to notify the motor to stop/continue. The part numbers in the bill of materials for the belt and gear: #17 and #25, respectively.

• Mechanical Analysis: The assumption of a uniform load appears suspect, and only a fraction of the load is shown as acting on the food, which is incorrect. Please provide a free body diagram of the food and explain how the load is found. If friction is assumed negligible and the force is normal to the surface, than the vertical component of that force must be sufficient to balance the weight of food at that point.
  • The mechanical analysis has been edited. The equations defining deflection and slope are changed for a system with a linearly varying intensity of load, as opposed to the uniformly distributed load. The load is found in the attached free body diagram. The fins contact the food at an angle, as opposed to contacting it directly opposing the weight. Therefore, there is a force contacting food from the right, as well as the weight of the food. The fins must counteract both of these forces, so it is greater than the weight. The force of the fins on the total sum of the food is found using the angle of the fins, which is 45 degrees to the plane parallel with the floor.

• How is your solution sensitive to the Young's Modulus, within the likely range that you mention?
  • The slope and deflection values are related to Young's Modulus, inversely and linearly. That is, as Young's Modulus increases, slope and deflection decrease. The Young's modulus is large for materials that are difficult to bend or twist. Since the fins are easy to deflect, a small value for Young's Modulus is expected, small meaning relatively less than the value for steel or other values that deflect less.

• Once you have found the answer for deflection, how do you interpret this result in terms of design implications?
  • Our choices for future improvements depend on the results of the deflection calculation as the fins and the feeder structure are designed so that there is a gap located in the opening where the food falls into the bowl. This gap is large enough so that sometimes the food could fall through the gap into the bowl, while other times the food will be stuck in the gap. With the gap approximately 1cm in width, a deflection of 1 mm could influence how much food would fall through. Therefore, redesigning the dispensing mechanism is intended to be part of the prototype, in that removing the gap aspect will improve consistency in portion sizes, as well as determine whether certain sizes of food are required.

• Bill of Materials: Good.

• DFMA: Good observations.

• FMEA: Good observations - the peace-of-mind aspect of confirming to the owner that the animal has been fed could be a great angle for innovation.

• DFE: Interesting that dog food emissions dominate. This seems to imply that reducing waste may be the best way to reduce impact - is there any food waste associated with the product? Does the production of batteries that you have included in the use phase include the electricity that is stored in the batteries and used by the device, and would the use phase differ much if the device were plugged into the wall instead?
  • Added ideas on reducing waste. The production of batteries included does include the electricity stored in the batteries. We do believe that the use of an ac adapter would lower the waste/GHG emissions but since one is not included with our product it wasn't considered. However our redesign will include an ac adapter that should reduce waste.

• If any of your images, figures, or text were taken from another source, please be certain to provide proper attribution.
  • Response to this question