Case Studies
Analysis
Kinematics
Stress Engineering Services (SES) designed a joint that could articulate freely, lock at an angle, provide two independent axial inputs greater than 200 pounds and fit within a 12mm trocar. We started with basic concepts and hand calculations of strength. Using this as the foundation, CAD models were constructed of the concepts. Multiple design iterations were assessed using virtual prototyping, where the mechanism behavior was simulated using finite element analysis (FEA). SES refined the features and performance of the device in FEA before confirming via testing of physical prototypes.
Assembly Impact
SES analyzed the packaging for a disposable medical instrument and experimentally developed a failure criterion for the package seal. We constructed and analyzed finite element models of the device and the package being dropped on the floor and verified the results of the analysis experimentally.
Tolerance
SES designed a mechanism to be created from injection molded plastic parts. A tolerance study was performed to predict whether the components could be reliably assembled. A second tolerance study was performed that combined kinematics and dimensional variations to predict the range of efficiencies of the final assembly. This was used in a trade study prior to modeling in 3-D CAD.
2-D CAD and tolerance representation of a gear and pawl:
Nominal and +/- 3 s mechanical advantage curves of a gear assembly (assembly not shown):
