Pill Cutter - Progress Blog 8: 4/16/2022

Hello and welcome back to our team's fourth blog post of 2022! We are the University of Houston's Mechanical Engineering Capstone Team 35: Progress Blog 8.

First off, we would like to talk about our team's accomplishments. Thus far, the team has fabricated and assembled a completed physical working prototype of the device. The prototype consists of five components; the device base, the container with secondary blades, the multi-shapes disk, the cutting arm, and the blade. The multi-shape disk consists of 9 different shapes with 5 holes of different sizes where the pill can be fitted. The secondary blades provide middle support to the pill and ensure the pill is laying on an even surface. The cutting arm contains a curved blade that distributes the applied stress on the pill more evenly to produce cleaner cuts. The container has 5 individual spaces for the user to be able to store different types of pills if they wish. The device is assembled and secured using permabond food-grade adhesives. The completed physical working prototype is shown below in figure 1.

Figure 1: Assembled physical working prototype

In figure 2, the operation of the device is shown, with the pill being aligned to cut with the curved blade. Figure 3 shows the result of this cut compared to the cut of the same pill with a different pill cutter; the team’s device produces a clean-cut and reduces mass loss of the pill by avoiding crushing while the other pill cutter crushes the pill since the pill does not have room to move as it is being cut.

Figure 2: Device in operation

Figure 3: Cutting comparison

The team has conducted 4 out of 5 validation tests, and three out of the four procedures were successful. The overall validation tests are shown below in table 1. There were fourteen different pills used during all the validation tests (shown in table 2). Out of all five validations, test three's fall resistance is the only test that the team has yet to conduct. The delay is due to the unsatisfied result of test two being 97 percent above the constraint value. The unsuccessful outcome results from a lack of grip between the pill and the surface where the pill lays on the device, resulting in the pill slipping, causing the pill to move while it is being cut and producing an angled cut. As for the rest, test one's mass loss shows exceptional results with 74.7 percent below the constraint value; test four applied force yielded 56 percent below the constraint value. To determine whether the applied force on the device would be less than 29 N, the team determined the mechanical advantage of the device is about 4.0; since the hardest pills have an average fracture strength of 98 N, the applied force to cut this type of pill would be 24.5 N, which is less than the maximum force of 29 N the team required for success in this test. Lastly, test five (weight, dimension, and volume) fulfilled the constraint shown in table 2.

Table I: Overall validation test results

Table 2: Pills used in validation tests

Table 3: Weight, dimension, and volume

As for the remaining tasks ahead, the team needs to pinpoint solutions to improve test two's results. The team plans to add a thin piece of rubber to the fin to increase friction between the pill and the laying surface to prevent movement during the splitting process. Furthermore, test number three also needs to be taken care of, but once all the validation tests are complete, the team will move forward with the completion of all delivery items. These include the instruction manual for the device as well as the final report of our capstone project.