WRENCH FIXTURE
April 2021 - June 2021
The wrench fixture project was part of a class at Northwestern called DSGN 386: Manufacturing Engineering Design. On a team with 3 other people, the project's goal was to design, machine, and create an assembly fixture that facilitates efficient assembly of a size-changing wrench. More specifically, the fixture was intended to make component placement more foolproof, control how tightly an orbital riveting machine fastened parts, and maximize productivity (units produced/(# of workers x time)). Throughout the project, the team utilized lean design and lean manufacturing principles to plan wrench assembly and to inform the fixture design.
The project's culmination was a production "test run" where the team's manufacturing plan was put into action: their selected number of workers assembled wrenches in an assembly line using the team's fixture, for a fixed amount of time. The final number of non-defective units produced was then used to measure productivity.
SKILLS
Fabrication
Laser cutter, orbital riveting machine, manual mill, conversational mill
Metrology
Optical comparator, calipers, hole gauges
Manufacturing Methods
Product deconstruction, stamping
Lean Manufacturing and Design
Value stream mapping, root cause analysis
CAD
3D CAD models (Siemens NX), 2D CAD drawings (Siemens NX), GD&T
Assembly
Fixtures, riveting, tolerance analysis, DFA, BOMs
DESIGN CRITERIA
The fixture will...
Facilitate correct placement of individual components
Fix the rivets at a height that produces a functional wrench (i.e., not too tight or too loose)
Hold rivets in place as the assembly is moved to the orbital riveter
Be capable of aligning each rivet under the orbital riveter
DESIGN
The pins to be riveted are placed on the first fixture (in their shallow holes), followed by the two plates. An orbital riveting machine is used to rivet the two plates together
The assembly's remaining pins are placed on the second fixture, and an outer plate component is then placed so that those pins go through its holes
The inner-plate riveted sub-assembly is placed on top of the outer plate, followed by another outer plate to sandwich that sub-assembly
The fixture is lined up on the orbital riveting machine using an acrylic component
The full assembly's rivets are done using the orbital riveting machine. The fixture plate is moved along the acrylic component's path in order to flatten the wrench's different rivets
The wrench is removed from the fixture and a spring is added to the assembly
The wrench handles are squeezed for a brief functionality test
