Jelani Roberts

Project Type: Manufacturing

The Task: “From art to Part”

Every year Northwestern partners with a local school to bring the toy ideas of elementary school children from their initial art to usable toys. Using CAD, CNC milling and injection molding, our group design and manufactured a small production run of toys.

Computer Aided Design

Using CAD software, we designed a 3 part cupcake. Knowing that we needed to mill molds for each of the parts, the geometry of the cupcakes was carefully chosen as to have no overhangs or features that could not be reached by a 3 axis mill.

To fit the parts together, tabs were placed on the edge of the icing and cake parts. The dimensions of the tabs were carefully considered so that they would form an interference fit when the parts were pushed together. However, we also had to consider the size of the available milling tools, which determined the depth and with of the tabs.

Computer Aided Manufacturing

The CAD models of the cupcake were added and subtracted to an uncut mold to create the molds for our cupcake. Once the molds were complete we generated tool paths using our available tools, starting with half inch end and ball mills to quickly cut the large geometry and finishing the small details with mills as small as 1/16 of an inch. Once the tool paths were finalized and converted to gcode, the mold blanks were machined using a 3 axis CNC mill.

Injection Molding

Despite our best efforts, the molds were not perfect aligned when the were mounted on the injection molding machine. To compensate, the molds were shimmed until they were properly aligned. Once the molds were shimmed, and a production run of 150 parts was made.

At the end of the quarter my team and I were excited to deliver a bunch of toy cupcakes to our professor to give to the local elementary school kids who inspired our designs. In the process of designing and delivering these toys, our group learned a tremendous amount about computer aided design and manufacturing. We furthered our skills in solid modeling, learned to design usable injection molds and turn those models into tool paths. Once the design was done, we learned set up and operate 3 axis CNC mills, and injection molding machines to make those designs a reality. Even more importantly, we gained a newfound respect for the manufacturing precision required in the production of seemly simple objects, and the skills to troubleshoot the errors that inevitably arise. This respect for the challenges of manufacturing has made me more aware of the importance for designing for manufacturers in addition to end users, and continues to influence how I design physical products.