In this unit, students learn methods to physically join parts in an assembly, including mechanical fasteners, adhesives, press fits, and hinges. They learn about different types of fit and how to specify tolerances to achieve desired fits between interacting parts. Students then learn how to assemble parts using CAD and create simple bottom-up assemblies that realistically simulate physical mechanical systems. Assemblies are documented in CAD with assembly drawings. Students apply engineering principles and practices to reverse engineer and improve a consumer product by disassembling and analyzing a product or system to understand and document the visual, functional, and/or structural aspects of its design. Students will also conduct a case study of a common consumer product to identify potential ways to improve the manufacturability and ease of assembly of the product. Students will also use top-down modeling to model the consumer product students have reverse engineered. They will apply the design process again to design and prototype (3D print) an integrated accessory for the reverse engineered product and present the design.  Finally, in this unit students investigate a variety of materials through experimentation and are tasked with selecting materials to serve a specific purpose. The types of materials investigated include wood, metals, ceramics, plastics, and composites to identify properties that may impact material selection. Properties investigated can include density, conductivity, strength, flexibility, hardness, and so on. Students learn how to assign specific materials to CAD models and to differentiate between assigning the physical properties of a material to a part and only changing the visual appearance of the part. Students work within a team to imagine the future through research of innovative materials and the redesign of a product using advanced materials.  Lastly, students work collaboratively to reverse engineer and troubleshoot a non-working, multi-component mechanical device. Then, team members work together to redesign the device, produce working drawings, and produce new parts to correct the design and manufacture a working physical model.