Pressure-Balanced Bottle Insert for Leak-Free Pouring. A food-safe, removable insert for standard glass bottles that enables smooth liquid outflow while automatically regulating internal pressure to prevent glugging, using a rib-sealed nozzle system printed in TPU.
This project addresses the common problem of liquid "glugging" when pouring from glass bottles. The insert converts standard glass bottles into smooth-pour containers by creating a dual-channel system that allows air to enter while liquid exits, mimicking the behavior of sports caps or Gatorade-style inserts.
| Feature | Description |
|---|---|
| Material | Flexible TPU printed at 100% infill (Shore 95A–98A) |
| Count | 3–5 stacked ribs along the length of the insert |
| Angle | Each rib is angled at 20–30° upward relative to the base (think of a backward umbrella) |
| Shape | Rounded triangle cross-section, with a bulbous tip to compress against bottle walls |
| Function | Prevent vertical movement and leakage; create dynamic pressure seal when liquid moves around insert walls |
Design Insight: Sharp ribs failed or tore easily; gradual curves with reinforced bases increased lifetime and seal quality.
User Feedback Consideration: Large openings led to messy splashing. Small openings caused gurgling or required tilting too far.
Design Challenge: Too large = leaks when tilted. Too small = backpressure buildup and gurgle.
| Parameter | Setting |
|---|---|
| Printer | Prusa MK4 |
| Material | Food-safe TPU (Shore 95A–98A) |
| Nozzle | 0.4mm |
| Layer Height | 0.15mm (0.1mm for ribs or vent area) |
| Infill | 100% solid |
| Supports | Tree supports only under dome + vent hole |
| Bed Temp | 50–60°C |
| Nozzle Temp | 235–245°C |
| Print Speed | 20–30 mm/s |
Over 70 design iterations were developed, printed, and tested across several months.
| Version | Failure Point | Cause |
|---|---|---|
| v1–v10 | Fell into bottle | Ribs too short or shallow |
| v11–v18 | Airlock when pouring | No air channel |
| v19–v25 | Leakage around seal | Rib profile too sharp; ribs tore |
| v26–v39 | Glugging returned | Vent hole misplaced or mis-sized |
| v40–v54 | Splashing pour | Opening too wide or too high |
| v55–v65 | Seals failed over time | Repeated compression weakened ribs |
| v66–v72 | Still leaks when shaken | Need for secondary sealing lip above ribs |
| Category | Specific Challenge | Solution/Learning |
|---|---|---|
| Fit & Retention | Keeping insert fixed under pressure without adhesives | Use flexible multi-rib stack with increasing radius profile |
| Airflow Tuning | Creating a vent that doesn't leak under tilt but still allows air | Side-channel placed just below the dome opening with directional slope |
| User Comfort | Creating a smooth pour without sudden gushing or needing hard tilts | Added a venturi taper and dome curvature, improved spout control |
| Leak Prevention | Liquid seeping around ribs or through vent under pressure | Used tighter rib fit and added internal lip above final rib layer |
| Food Safety | Material needed to be safe for contact, and durable | Food-safe TPU sourced, cleaned with isopropyl alcohol post-print |
| Manufacturing Repeatability | Ensuring prints consistently matched thread/neck sizes | Used calipers on bottles, created parametric sketch in CAD for scaling |