Steerable Sheath Torque RCA

Mission

Root-cause investigation into elevated steering torque in a steerable sheath system. Developed and executed structured testing to isolate shaft, handle, sterilization, and component-level contributors to torque variability.

Problem

Designed a structured RCA workflow and evaluated contributing factors including warm water conditioning, screw-and-nut assembly design, clamshell interaction, O-ring lot variability, sterilization, dwell time, shaft liner properties, braid density, and simulated use.

Approach

Used DOE-style testing, randomized O-ring comparisons, pre/post sterilization evaluation, handle-only and full-sheath testing, and torque measurement at defined angular positions. Tested multiple sample groups and compared component-level behavior to full-assembly performance.

Key Findings

Torque variability was most strongly linked to shaft interaction effects, screw-and-nut geometry, O-ring behavior, and sterilization sensitivity. The RCA also separated component-level contributors from full-assembly effects so design changes could be prioritized.

Outcome

Identified the strongest contributors as shaft interaction, screw-and-nut design, and O-ring variability. A screw-and-nut design change reduced torque contribution and improved expected design validation performance. VOC testing was also used to understand physician perception of acceptable torque ranges.

Project Impact

The work created a clearer technical basis for torque-related design decisions, connected bench measurements to physician feedback, and helped focus validation strategy on the contributors most likely to affect user experience and product robustness.