Shredding for Kicks
Engineering students use senior capstone to assist with alum's business and help keep plastic out of landfills.
The life span of a sneaker depends on its use. Running or walking, sport or recreation, function or merely fashion—they all wear out eventually. If they haven’t been completely worn out, sneakers may end up in a used clothing bin. More than likely, though, they will end up in a landfill, where it takes decades for them to degrade.
Penn State graduate Nick Unis is working to break that cycle. For the past several years his company, UnisBrands, has been making shoes using recycled plastic and 3D printers and in February 2020 added sneakers to the line. “We take water bottles, grind them down, and make them into the shoes,” he says. “Once they’re done wearing the shoes, customers can return them. We shred the shoes; customers then can get a discount on their next pair.”
UnisBrands's old shredder
Credit: Penn State
For such a business model to succeed, having a high-quality shredder is imperative. The company’s existing shredder had some serious limitations and needed a significant upgrade. Craig Brennecke, professor of practice, engineering, describes it as being like “a pair of scissors that won’t cut, that will bend the paper.” Under Brennecke’s guidance, two Penn State Altoona electro-mechanical engineering technology (EMET) majors, Sara Roselius and Kyle Knowles, tackled those limitations as their senior capstone project, clearing several hurdles along the way.
The project goal was to create a shredder that could shred the soles in a way that the rPET (recycled polyethylene terephthalate) would not “gunk it up,” Roselius explains. “This material’s properties are very different, very flexible. It will want to bend and fill the gaps of the shredder. We needed to find the point that will create shear action.”
For their first hurdle, the students ended up redesigning and rebuilding the shredder, Knowles says, which was “the most difficult and time-consuming part” of the project. Normally for capstone projects, “you spend the fall prepping but we spent that whole semester trying to get the shredder to work.”
When they received the original shredder, it had no safety features. In their reworking, “we created a bed with a rotating blade, adding a programmable logic controller (PLC) and a human-machine interface (HMI),” Roselius says. But because “the shredder is dangerous; it can rip apart flexible material,” the students added safety relays and even used a 3D printer to make a “plunger” to push the sole material into the shredder, Knowles adds.
In addition to the shredder, the students needed to figure out a mechanism to help sort the different sole colors, which Knowles says was his main focus. That meant coming up with the design, which ended up being a chute that rotates to the appropriate bin. Originally they considered rotating the bins instead of the chute but they realized the final configuration “would be easier to troubleshoot, easier to fix,” he says.
Knowles then “had to figure out the [sorter] dimensions, how it would fit under the table.” He also worked on the bins for the shredded material. “We couldn’t find anything on-line that had the shape and dimensions that we needed,” so he took matters into his own hands. “I heated up acrylic for a whole day and bent it into the shapes.”
Probably the biggest potential hurdle to completing the project was the campus shutdown and switch to online learning in mid-March, which closed the PSU labs. However, working on a Commonwealth campus has many benefits—in this case, according to Brennecke, “the students were so appreciative to work with PSU Altoona Lab staff to complete their project,”
Size turned out to be an unanticipated hurdle as well. They had planned for a four-foot shredder table, assuming the facility had a double door, Brennecke says, but they had to reduce the size when they learned the doors were all single-door width. Brennecke acknowledges the attention the students paid to the company’s needs: “Kyle and Sara didn’t just want to create a design to complete their capstone project, they were conscientious that the project would work at its best for UnisBrands.”
UnisBrands's new shredder, a senior EMET capstone project by Sara Roselius and Kyle Knowles.
Credit: Penn State
Unis is looking forward to bringing the final product to his company. Roselius and Knowles took a shredder that, he admits, “wasn’t functional at all and they brought it to the point where all the bugs are worked out. They were very dedicated to getting it perfect. Hopefully, we will get it within the next month,” a time frame depending on the reopening of the university.
Roselius is very positive about her experience. “Kyle and I developed and designed everything with the guidance of Penn State,” she says. Even when she says, “they let us fail,” she understands the value of that: “It was such a growing experience. They kind of shape you for that. You have all these mental tools ready to go.” She credits Penn State Altoona’s EMET program for her success: “Through the EMET course, I’ve had experience that helped me get my internship last summer. It helps with your confidence and problem-solving. The junior-year internship is [located] somewhere you want to work; it’s an investment to me and the company.”
While Roselius and Knowles have completed their work, they have ideas for the shredder’s future: a small band saw to cut pieces that are too large to fit in the shredder and an air compressor so that any small parts that don’t pass completely through the shredder can be blown out. Those items can be easily added to the shredder table in its present design—which is good because with two new shoe collections planned for release in the fall UnisBrands is going to need that shredder.
Throughout the project, Brennecke was very impressed with Knowles’s and Roselius’s performance. “As a team, they were one of the best that I have advised since joining Penn State. It was always a pleasure to sit down for our weekly meetings and discuss the details of their project. By the end of the first of two semesters, they had already designed their project and were deep into the machining of components for the final project.” And in two semesters—even with one truncated—the hurdles were cleared.
