Introduction
Guidance for designing Dual-Lobed Seals to reduce insertion force in medical devices. Medical device engineers face a common challenge: standard O-rings and gaskets often require excessive insertion force, leading to difficult assembly, risk of component damage, and higher manufacturing costs. In delicate applications like catheters, drug delivery systems, and microfluidics, a more flexible, precision-molded seal is needed.
This is where dual-lobed seals come in. By reducing contact pressure while maintaining an effective seal, these seals allow for easier insertion, better performance, and longer device lifespan.
This guide explores:
- Why insertion force matters in medical device design
- How dual-lobed seals reduce insertion force while maintaining sealing integrity
- Key design parameters for optimizing seal flexibility
- Material selection for biocompatibility and sterilization resistance
1. Why Insertion Force Matters in Medical Devices
In medical device design, excessive insertion force can lead to:
- Difficult Assembly → Increases manufacturing time and cost.
- Component Damage → Rigid seals can damage soft plastic housings, tubes, or precision parts.
- Patient Discomfort → High insertion force can cause tissue irritation in implantable or wearable devices.
Dual-lobed seals solve these issues by reducing friction and optimizing contact pressure during insertion.
Applications That Benefit from Low-Insertion Force Seals
- Catheters & IV Systems – Ensures smooth tube-to-connector transitions.
- Drug Delivery Devices – Prevents leakage while minimizing force needed to insert cartridges or syringes.
- Microfluidic Diagnostic Systems – Reduces stress on precision-molded channels.
- Implantable Medical Devices – Prevents tissue damage and ensures biocompatibility.
2. How Dual-Lobed Seals Reduce Insertion Force
A dual-lobed (hourglass) seal differs from standard O-rings by having two sealing edges with a flexible center section.
Key Benefits of the Dual-Lobed Design:
- Lower Friction During Insertion → The reduced cross-sectional contact area decreases resistance by 20-40% compared to O-rings.
- Controlled Compression → The hourglass profile allows for gradual deformation, making it easier to insert into mating components.
- Reduced Wear & Tear → Lower contact pressure means less material fatigue over repeated cycles.
Designing for Optimal Performance
- Lobe Height & Thickness → Thinner lobes reduce insertion force but may require higher compression for sealing.
- Flexible Center Section → Allows the seal to deform and recover, improving ease of assembly.
- Lead-In Chamfer → A 10-15° chamfer at the sealing edge can further lower insertion force by 10-15%.
3. Key Design Parameters for Optimizing Seal Flexibility
To ensure that the dual-lobed seal functions as intended, designers must carefully balance geometric tolerances, material selection, and surface finish.
✔ Geometric Considerations
- Lobe Angle: 45-60° for the best balance of low insertion force and sealing integrity.
- Lobe Thickness: 0.3mm to 1.5mm depending on the application; thinner lobes reduce insertion force but may require more compression.
- Cross-Section Tolerances: ±0.025mm for standard medical applications, ±0.010mm for microfluidics or implantable devices.
✔ Groove Fit & Compression
- Compression Target: 15-25% compression to ensure a tight seal without excessive resistance.
- Groove Width: Should be 5-10% wider than the uncompressed seal width to allow for expansion.
- Axial vs. Radial Sealing: Ensure proper groove depth for either radial or axial sealing based on the device’s design.
4. Material Selection for Biocompatibility & Sterilization Resistance
Medical seals must be biocompatible, sterilization-resistant, and flexible. The best materials for dual-lobed seals include:
| Material | Key Benefits | Sterilization Methods |
|---|---|---|
| Liquid Silicone Rubber (LSR) | Ultra-soft, biocompatible, durable | Autoclave, gamma, EtO |
| Fluorocarbon (FKM, Viton®) | Chemically resistant, flexible | Gamma, EtO |
| EPDM | Excellent steam and hot water resistance | Autoclave |
| Polyurethane (PU) | High wear resistance, durable | Limited sterilization |
- LSR is ideal for implantable seals due to its low durometer (as soft as 10-30 Shore A).
- FKM works best for chemically aggressive environments like drug delivery systems.
5. Quality Inspection for Dual-Lobed Medical Seals
✔ Dimensional Tolerances & Surface Finish
- Cross-section tolerance: ±0.015mm for tight-tolerance medical applications.
- Surface roughness: Ra < 0.4µm for implantable or fluid-contact seals to prevent bacterial adhesion.
- Flash limit: Less than 0.05mm to avoid excess material interfering with sealing performance.
✔ Friction & Compression Testing
- Insertion force testing – Measures force required to insert the seal into a defined groove or housing.
- Compression set testing – Ensures that after 72 hours at 150°C, the seal retains at least 90% of its original shape.
- Elongation & tear resistance – Critical for seals used in repeated insertion/removal cycles.
Key Takeaways for Designing Low-Insertion Force Seals
- For easier assembly in medical devices, use a dual-lobed seal instead of a standard O-ring to reduce insertion force by 20-40%.
- Optimize lobe thickness, angle, and groove fit to balance sealing performance and flexibility.
- Choose the right material based on biocompatibility, sterilization requirements, and flexibility needs.
- Ensure quality control with tight tolerances (±0.015mm), surface roughness (Ra < 0.4µm), and compression testing.
In need of Dual-Lobed Seals to Reduce Insertion Force?
For custom low-friction, precision-molded seals, consult sealing specialists to optimize material selection, geometry, and manufacturability for your application.
