Integrated Diving Mask: A Deep Dive into the Lens-and-Frame Co-Injection Molding Technology
Abstract
An integrated diving mask fuses the lens and the skirt directly into an inseparable single unit through injection overmolding, completely eliminating the independent plastic lens frame and adhesive seams found in traditional structures. This paper provides an in-depth analysis of the structural principles, material systems, and core process paths of lens-frame integration. It focuses on the mainstream technical route of PC lens plus liquid silicone rubber overmolding, revealing the unique advantages of “co-injection molding” in terms of sealing reliability, production efficiency, and structural lightness. The complete technical chain—from mold design and interfacial bonding to process parameter control—is systematically examined. Through case studies of iconic products such as the Beuchat Super Compensator, TUSA Zensee Pro, and Aqualung Reveal, this paper presents the evolutionary path and engineering value of integration technology in modern diving masks.
1. Introduction
The structure of a traditional diving mask can be summarized as a “three-piece set”—lens, frame, and skirt. The frame serves as the supporting skeleton, the lens is embedded in the frame, and the skirt is attached to the frame via adhesives or mechanical clamping. While this structure appears to have a clear division of labor, it hides unavoidable engineering flaws: the interface between the frame and the skirt is a physical seam. Aging adhesives, loosening mechanical clamps, or mismatched thermal expansion/contraction can all develop into leak points during long-term use.
The lens-frame integrated molding technology (also known as “co-injection molding” or “overmolding technology”) was born precisely to solve this fundamental problem. Its core idea is simple yet revolutionary: eliminate the seam. By precisely placing a pre-fabricated PC lens into a mold and then injecting liquid silicone rubber into the cavity, the silicone “embraces” the outer edge of the lens as it cures, forming in a single shot a seamless integration of lens and skirt. The independent frame is completely omitted in this process, reducing the traditional three-piece mask structure to a one-piece lens-skirt unit.
The Beuchat Super Compensator mask is a typical representative of this technology. Its product description explicitly states: “Frameless mask using an injection-molding technique where the skirt is molded directly onto the lens. The edge of the skirt is chemically welded to the lens (injection-molding technique): the lens cannot be removed, making the mask more robust and durable.” This technical path is now spreading from high-end professional products to the mainstream market, becoming an important direction in modern diving mask manufacturing.
2. Technical Principles and Material Systems
2.1 Essential Definition of Lens-Frame Integration
"Lens-frame integration" does not mean that the lens is fused with a separate plastic frame — in fact, in an integrated diving mask, the independent plastic frame is completely eliminated. A more accurate description is that the lens is directly bonded to the silicone skirt at the molecular level through in?mold overmolding. The skirt not only performs the sealing function but also assumes the structural support role traditionally played by the frame.
Take the well?known Beuchat Super Compensator as an example: "Frameless mask using an injection?molding technique where the skirt is molded directly onto the lens." This is what the industry calls a "frameless design" — there is no central nose clip or frame, so the field of view is unobstructed. Thanks to its frameless technology and the buckles mounted directly on the skirt, the mask is more robust and durable.
This design concept also narrows the overall profile of the mask. The frameless technology and the angled lens design help reduce internal volume, so divers do not have to counteract excessive mask compression when equalizing ear pressure. The connection between the skirt and the lens is a "chemical weld"; the lens cannot be removed, ensuring the sealing integrity of the mask from a structural standpoint.
2.2 Material Selection: The Golden Combination of PC and Liquid Silicone Rubber
The material selection for integrated diving masks follows one principle: the rigid, transparent material provides the view and structural anchoring, while the soft, elastic material provides sealing and comfort.
PC (polycarbonate) is the mainstream substrate for the lens, with light transmittance exceeding 92%. PC has very high impact resistance, meeting the stringent requirements for diving mask lens impact performance. Compared to glass, PC is easier to bond and overmold with other materials during processing, and it can be precisely injection?molded into various complex curved shapes.
Liquid Silicone Rubber (LSR) is the ideal material for the skirt. Food?grade LSR with dual FDA/LFGB certification has "zero odor, zero fluorescent agents, and is non?allergenic when in contact with the face." Its hardness can be adjusted to a soft range of 40±5 degrees, conforming to facial contours like a "second skin." LSR exhibits excellent chemical resistance, UV aging resistance, and tensile resilience, perfectly coping with the multiple stresses and corrosive factors in a diving environment.
2.3 Introduction and Evolution of "Co?Injection Molding"
The integrated manufacturing of lens and skirt is not a completely new concept. As early as 2002, patent literature contained detailed descriptions of "placing a PC lens into the cavity of a soft mask mold, injecting soft mask silicone material, with injection temperature controlled below 250?°C and injection pressure controlled at 50?T/cm2." This process was defined as a "co?injection product," and its value was summarized as "not only simplifying the production process but also effectively increasing sealing and leak?proof strength," achieving "100?% leak?proof for both air and water."
Extending this concept further, the patent technology for "a swimming, surfing, and diving mask" demonstrates another implementation path: the soft mask is injection?molded on the inner side of the frame using a dedicated mold and unique process. The mask, lens, and frame are co?injection molded in one shot, and an adhesive layer applied between the contact surfaces enables a high?strength bond among the three components during curing. The patent notes that this technology offers comprehensive advantages of "high production efficiency, excellent robustness and leak?proof performance, and low cost."
3. Core Process Path: From Mold Design to Finished Product
3.1 LSR Overmolding on PC Process
Currently, the LSR-over-PC process has become the mainstream technical solution for manufacturing integrated diving masks. Its process flow is roughly as follows:
Step 1: Pre-positioning of the PC lens. A high-transmittance PC lens (transmittance ≥92%) is obtained by conventional injection molding or cutting. The edge of the lens is typically designed with microscopic undercuts, grooves, or ribs to provide mechanical interlocking points for subsequent silicone overmolding. Manufacturers need to equip precision positioning systems to accurately place the lens at a predetermined position in the mold cavity.
Step 2: Mold closing and silicone injection. After the lens is positioned in the mold, the injection molding machine injects liquid silicone rubber into the cavity. The LSR undergoes a crosslinking reaction during high-temperature vulcanization, forming a strong bond with the PC lens after curing. Throughout the injection process, the melt temperature is controlled between 200?°C and 250?°C, and the injection pressure is kept within the range of 40?T/cm2 to 50?T/cm2 — excessively high temperature or pressure may deform the PC lens, while too low values may affect silicone vulcanization and interfacial bond strength.
Step 3: Achieving key quality indicators. A high-quality LSR-over-PC process should meet the following technical specifications: silicone layer thickness uniformity error ≤0.03?mm, water resistance rating meeting IP68 standard (no water ingress after 24?hours of immersion). This level of precision and waterproof capability is achieved through advanced methods such as "three?axis vision?guided overmolding" — the injection mold is integrated with a vision inspection system that accurately positions the lens before injection, ensuring consistent silicone layer thickness everywhere.
3.2 Interface Bonding Technology: From Mechanical Locking to Chemical Welding
The bond strength between the lens and the skirt is the fundamental guarantee of long?term sealing reliability for integrated masks. Existing technologies achieve bonding through two main approaches:
Mechanical interlocking is the most basic bonding method. Microstructures such as undercuts, grooves, and ribs are pre?formed on the edge of the PC lens. After curing, the liquid silicone rubber flows into these structures and solidifies, creating a "snap?lock" effect. This physical interlocking effectively resists shear stress and prevents separation of the interface during kneading, squeezing, or pressure changes.
Chemical welding represents a higher?level bonding technology. Beuchat's mask products explicitly mention that "the edge of the skirt is chemically welded to the lens (injection?molding technique)." This is typically achieved by applying a primer or adhesive to the edge of the PC lens before injection — research shows that brushing or spraying LHD?306 primer onto the surface of the PC sheet to be bonded, drying it at 80?°C–100?°C for 10–15?minutes, and then co?vulcanizing it with silicone rubber in the mold results in the PC and silicone rubber becoming a single integrated piece after demolding. This treatment allows the silicone to form chemical bonds with the PC surface during curing, achieving true molecular?level joining.
Some advanced manufacturing processes also employ a "dual?flexible?layer" design: first, a first flexible silicone layer with multiple protrusions is formed on the lens edge. These protrusions keep a certain distance between the first layer and the mold, preventing the high?temperature mold from causing the first layer to detach from the lens. Then, a second flexible silicone layer is formed over the first layer, with the protrusions exposed outside the second layer, thereby allowing flexible changes in the mask's design and shape.
3.3 Special Treatment for Glass Lenses: Plastic Sheet Protective Layer
When the lens material is glass instead of PC, the manufacturing process faces an additional challenge — glass is prone to cracking due to stress concentration during mold clamping. One patent technology proposes a targeted solution: attach a plastic sheet around the periphery on one side of the transparent glass lens. The plasticity of the plastic sheet reduces damage to the glass lens caused by mold clamping. At the same time, the plastic sheet is designed to protrude beyond the accommodating groove, so that when the glass lens and mask are integrally molded in the mold, the injected silicone does not overflow from the surface of the plastic sheet, thus avoiding quality issues in production.
The specific steps of this process include: first, fabricate the glass lens and the plastic sheet; attach the plastic sheet to the periphery of the glass lens using adhesive; then place the glass lens with the attached plastic sheet flat into the mold; finally, inject silicone through the injection molding machine. The silicone flows along the outer edges of the glass lens and plastic sheet inside the mold cavity to form the mask. This technical path removes manufacturing obstacles for using glass lenses in high?end integrated masks.
3.4 Collaborative Design of Rigid Support Structures and Soft Skirt
An integrated mask is not simply about "throwing a lens into silicone"; it involves precise collaborative design between rigid and soft parts. For example, a patent for a full?face snorkel mask proposes a lens module concept: the lens module has a lens portion and a support structure. The support structure is integrally formed with the lens portion, located at a distance inward from the outermost edge of the lens portion, and is connected to part of the waterproof skirt to enhance rigidity in the area near that part.
The rationale behind this design is that the soft waterproof skirt is subjected to pulling, squeezing, and other external forces during use. If certain functional components (such as one?way intake valves and exhaust channels) are made entirely of soft materials, they may deform and fail after excessive tightening during wearing or after long?term use. By integrally providing a support structure on the rigid lens portion, the rigidity of these soft functional components is enhanced precisely at assembly, ensuring accurate and reliable operation. "Multiple functional components can still be made of lower?cost, less?complex soft waterproof materials. They can even be molded together when the silicone waterproof skirt is produced, greatly reducing manufacturing and assembly costs."
4. Leading Product Case Studies
4.1 Beuchat Super Compensator
The Beuchat Super Compensator is a benchmark product that employs integrated injection molding technology. It features a single elliptical lens and a hypoallergenic silicone skirt. With no central nose clip or frame, the field of view is unobstructed, making it ideal for demanding applications such as underwater photography.
In terms of sealing, the edge of the skirt is chemically welded to the lens, making the lens non?removable. For comfort, padded equalization finger pockets ensure that only the nasal skirt section deforms during equalization (the rest of the skirt does not deform), so sealing performance is not affected. In structural durability, thanks to the frameless design and the buckles mounted directly on the skirt, the mask is more robust and durable. Additionally, the angled lens design reduces internal volume and optimizes upward visibility.
4.2 TUSA Zensee Pro
The Zensee Pro from TUSA is the brand's first frameless diving mask, incorporating a number of innovative technologies: UV 420 lens treatment to block harmful high?energy visible light, CrystalView optical lenses for superior color and light transmission, and an anti?reflective coating to enhance the overall visual experience.
For skirt technology, TUSA's Freedom Technology uses varying silicone thicknesses and stabilizing rib designs on the skirt surface, combined with a proprietary low?friction skirt surface, to improve fit and comfort. The 3D SYNQ technology embeds a unique conforming ring into the skirt, allowing the mask to adapt to various face shapes and provide an ideal fit and seal.
4.3 Aqualung Reveal UltraFit
Aqualung's Reveal series features Advanced Fit Technology (AFT), which creates different textured structures inside the silicone skirt, allowing it to better conform to any face shape, thereby improving sealing and comfort. Although Aqualung's specific process details have not been disclosed, this technology essentially falls within the same integrated lens?over?silicone construction, representing the industry's mainstream technical consensus.
5. Engineering Analysis of Technical Advantages
5.1 Fundamental Improvement in Sealing Reliability
The seal of a traditional mask relies on at least two seams: between the frame and the lens, and between the frame and the skirt. Each seam is a potential leak source — factors such as adhesive aging, loosening of mechanical clamps, and mismatched coefficients of thermal expansion can all create micro?gaps during long?term use. An integrated mask upgrades the interface between the lens and the skirt from a physical seam to a chemical bond, eliminating the primary sealing risk points and bringing the overall waterproof performance of the mask up to the IP68 standard.
5.2 Structural Simplification and Production Efficiency
From a production efficiency perspective, the integrated manufacturing process consolidates multiple steps into a single molding operation. The traditional three?piece structure requires separate production of the lens, frame, and skirt, followed by assembly processes to join them. This not only involves many steps and long cycle times but also suffers from accumulated assembly tolerances and defects occurring at different stages. The integrated process completes the entire front structure in one co?injection molding step, significantly shortening the production cycle and reducing overall costs.
5.3 Weight Reduction and Unobstructed Field of View
Eliminating the independent plastic frame yields a substantial weight reduction, providing noticeable relief for divers who wear the mask for extended periods. More importantly, the absence of the frame means there is no bulky structure in front of the face — the field of view is unobstructed. Upward visibility, in particular, is significantly improved because there is no thick frame blocking the top of the mask. This advantage is especially critical for freedivers and underwater photographers.
6. Challenges and Technical Outlook
6.1 Precision Boundaries of Process Control
Integrated manufacturing is not without challenges. During LSR overmolding on a PC lens, small deviations in parameters such as temperature, pressure, and injection speed can affect product quality. Excessive injection pressure may deform or crack the PC lens; improper temperature control can lead to incomplete or excessive vulcanization of the silicone. Uniformity of the silicone layer thickness must be ensured by high?precision in?mold positioning and vision inspection systems — the error must be controlled within 0.03?mm, imposing very high demands on mold machining accuracy and injection process control.
6.2 Trade?off of Repairability
The fact that "the lens cannot be removed" is both an advantage and a limitation of integrated masks. From a sealing perspective, it eliminates the root cause of leaks. From a repair perspective, once the lens is scratched or damaged, it cannot be replaced individually, and the entire mask must be discarded. This requires manufacturers to invest more effort in lens coating treatments (such as anti?reflective coatings and UV protection coatings) to extend the service life of the lens. It also encourages consumers to pay more attention to daily care of the mask.
6.3 Exploration of Sustainable Materials
As environmental regulations become stricter and consumers' environmental awareness grows, research into the application of biodegradable bio?based materials and recyclable thermoplastic elastomers (TPEs) in integrated masks is advancing. However, replacing materials while ensuring diving safety still faces technical challenges such as long?term durability and chemical resistance.
7. Conclusion
Lens?frame integrated molding technology represents an important evolution in diving mask manufacturing from "separate assembly" to "integrated molding." By co-injection molding a PC lens and a liquid silicone rubber skirt in one shot, this technology fundamentally eliminates the leak risks associated with physical seams in the traditional three piece structure, while also achieving weight reduction, an unobstructed field of view, improved production efficiency, and lower overall costs.
The essence of integrated manufacturing lies in the deep integration of three aspects: breakthroughs in materials science enabling molecular?level bonding between PC and silicone; precision mold design ensuring uniform silicone layer thickness and interfacial bond strength; and precise control of process parameters guaranteeing batch?to?batch consistency and long?term reliability. Product practice has proved that it comes from brands such as Beuchat, TUSA, and Aqualung demonstrate that this technical approach has reached quality levels sufficient for professional diving applications.
Looking ahead, as LSR overmolding technology matures further, intelligent in?line inspection methods become more widespread, and sustainable materials are introduced, integrated diving masks will continue to evolve toward lighter weight, greater personalization, and improved environmental friendliness, while maintaining core sealing reliability. For the diving equipment manufacturing industry, this is both an update in manufacturing philosophy and a technological evolution from "repairing seams" to "eliminating seams."
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