DOE-Driven Light Pipe + Diffuser Redesign
Overview
Role & Ownership
Redesigned a disposable light-delivery consumable used to administer Photodisinfection therapy. The legacy design relied on a fiber-optic assembly with specialized end prep/splicing and epoxied diffuser, driving high cost, long lead time, and variability in irradiance output. I re-architected the consumable to a PC injection-molded light pipe with a snap-fit diffuser interface, "Nose Cone", then ran a data-driven DOE loop using irradiance profile measurements to converge on manufacturable geometry. The final design improved performance while dramatically lowering cost and enabling higher throughput over the Medical Device's service life.
• Owned the end-to-end mechanical/PDE redesign from concept → design lock → supplier release
• Defined CTQs across optical output, fit/retention forces, and tolerance robustness
• Partnered with an overseas supplier (Korea) and state side vendor to develop prototype tooling with swappable inserts
• Drove geometry iterations via characterization feedback (DOE-style decision making)
• Created insertion/retention force targets and tolerance strategy for repeatable assembly
• Delivered drawing set and release package for production builds aligned to clinical timelines
Legacy Design
Re-Design
Approach
1. Requirements + CTQs: performance (irradiance/dose), disposable cost targets, robust assembly, and variation control
2. Architecture tradeoff: replaced fiber/splicing workflow with injection-molded components + snap interface 3. CAD + tolerance strategy: parameterized key features; applied GD&T and CTQ dimensioning on interfaces/locators 4. Prototype iterations: 3D printed fit studies to tune snap feel; converged mechanical interface targets 5. Characterization / DOE: measured irradiance profiles per geometry/material variant; identified high-impact variables 6. DFM + vendor/tooling + release: executed tool insert swaps → injection runs → data review → design updates → design lock + supplier package
2. Architecture tradeoff: replaced fiber/splicing workflow with injection-molded components + snap interface 3. CAD + tolerance strategy: parameterized key features; applied GD&T and CTQ dimensioning on interfaces/locators 4. Prototype iterations: 3D printed fit studies to tune snap feel; converged mechanical interface targets 5. Characterization / DOE: measured irradiance profiles per geometry/material variant; identified high-impact variables 6. DFM + vendor/tooling + release: executed tool insert swaps → injection runs → data review → design updates → design lock + supplier package
A: Iterative 3D printing cycle using Formlabs SLA to dial in incertion and retention force of Nose Cone to Light Pipe snap fit.
C: Nice little alignment feature
B: Initial Design geometry came from Ray Trace Analysis by working with 3rd party optical expert. By changing the angle of SMA interface, B, and Texturing surface of Light pipe tapered end I was able to tune the irradiance profile of the system. These Features were made as swappable core inserts in proto-mold for quick iteration runs.
Tolerance Analysis for optimimal diameter of light pipe and install distance to capture full beam from SMA NA.
Capturing Irradiance prorfiles at varying distances
Capturing Irradiance prorfiles at varying distances
Early Stage Custom Irradiance Measurement System
Early Stage Custom Irradiance Measurement System
Results
• COGS: reduced by ~87% by eliminating specialized fiber prep and enabling injection-molded disposables
• Performance: increased output to ~2× irradiance, achieving the same dose in ~50% of the time
• Manufacturing scalability: simplified assembly intent and reduced sensitivity to manual workmanship
• Program impact: parts produced and ready in time to support Phase III clinical trial builds