Materials and processes in eyewear: a heterogeneous landscape

Modern eyewear is characterized by a wide variety of materials: cellulose acetate, TR90, nylon, polycarbonate for frames; mineral glass and CR-39 for ophthalmic lenses; and light metals such as titanium and aluminum alloys for structural components. Each material responds differently to laser energy, and this response depends strictly on the wavelength of the source used.

From a manufacturing perspective, marking must meet both functional (traceability for regulatory compliance, inventory management) and aesthetic (brand logo, size and pattern indications) requirements. In many cases, the process takes place on curved surfaces or small components, making the accuracy and repeatability of the laser system crucial.

CO₂ laser: principle of operation and areas of use

The CO₂ laser emits infrared radiation at 10,600 nm, a wavelength that is absorbed very effectively by organic and polymeric materials. In plastic materials, the beam energy causes rapid surface vaporization, creating a sharp and highly visible etching effect. This characteristic makes CO₂ particularly suitable for marking acetate, TR90 and other plastics commonly used in frames.

A major advantage of the CO₂ laser is the speed of marking on thick plastics or extensive graphic layouts. However, the depth of penetration, if not controlled, can generate undesirable thermal deformation or color changes, especially on clear or translucent materials. In addition, CO₂ cannot be used on metals without prior surface treatments, limiting its use in mixed applications.

Another aspect to consider is the size of the laser spot. The CO₂, while effective over large areas, has a relatively large spot compared to the UV laser, which can be a limitation when small two-dimensional codes with high information density, such as the Datamatrix required for traceability according to international standards, need to be marked.

UV laser: principle of operation and application advantages

The UV laser, with a wavelength of 355 nm, acts through a mechanism known as photochemical ablation. The energy of the ultraviolet photon is high enough to break the molecular bonds of the material without generating significant residual heat. This process, termed “cold marking,” results in precise etchings with minimal heat affected zone (HAZ) and no deformation of the substrate.

In the context of eyewear, the UV laser is particularly advantageous in the marking of:

• Heat-sensitive plastics, such as polycarbonate or composite materials, where CO₂ would risk causing yellowing, micro-cracking, or loss of transparency.
• Ophthalmic lenses, where optical quality should not be compromised by thermal stress or microfractures.
• Clear or light-colored frames, on which the contrast obtained with the UV laser is generally superior, with no risk of surface burns.
• High-density two-dimensional codes, due to the very small laser spot (typically less than 20 µm) that allows marking of millimeter-sized Datamatrix with excellent readability according to the ISO/IEC 15415 standard.

An additional advantage of the UV laser concerns material versatility: in addition to plastics, the UV system is effective on glass, ceramics, and some coated metals, allowing a single technological solution for different stages of the production process.

Operational comparison: when to prefer one or the other technology

The choice between UV and CO₂ depends on a number of technical and production factors. If the goal is to quickly mark large logos on opaque acetate frames, the CO₂ laser is a proven and cost-effective solution. The process speed and low source cost make it suitable for high-volume production with simple graphic layouts.

In contrast, when working on delicate materials, transparent surfaces, or components requiring traceability with miniaturized two-dimensional codes, the UV laser becomes the obvious choice. The quality of marking, total absence of thermal stress, and the ability to work on mixed materials (technical plastics, glass, coated metals) more than compensate for the higher initial cost of the source and slightly longer cycle times.

A common mistake is to underestimate the importance of focus and working distance control. On curved frames or on lenses with complex geometries, the use of a three-axis scanning head or autofocus systems becomes essential to ensure repeatability of marking, regardless of the laser technology employed.

Online integration and practical considerations

In modern eyewear, laser marking is rarely a stand-alone process. Integration into automated assembly lines requires compact systems that can be interfaced with production management software (MES/ERP) and equipped with real-time quality control logic.

In this context, UV laser systems lend themselves better to integration with verification cameras for automatic grading of two-dimensional codes, a practice increasingly required by high-end manufacturers to ensure regulatory compliance and reduce waste. In contrast, CO₂ systems, while simpler to integrate mechanically, require more attention in managing the extraction of fumes generated by ablation, which may contain organic particulates and volatile compounds.

One aspect that is often overlooked is maintenance. State-of-the-art UV lasers (DPSS or solid-state) have a very high source lifetime (up to 25,000 operating hours) and require minimal routine maintenance. CO₂ lasers, while mature technologies, require periodic inspection of the condition of the laser tube and cooling system, elements that affect long-term operating costs.

Application examples and process parameters

To make the comparison more concrete, let us consider two real application cases. In marking an 8×3 mm logo on a matte-black TR90 frame, the CO₂ laser (power 30 W, focal length 160 mm) completes the process in about 1.5 seconds with a scanning speed of 800 mm/s, frequency 20 kHz, and power set to 70%. The result is a sharply visible white engraving without deformation.

In the same scenario, using a UV laser (power 5 W, focal length 160 mm), the time increases to about 2.8 seconds with speed 500 mm/s, frequency 25 kHz and power 85%. The contrast is slightly higher and the aesthetic effect “cleaner,” free of heat haloes, but the cycle is slower. The difference becomes even more pronounced when switching to a transparent polycarbonate frame: here the CO₂ tends to generate micro-cracks and opacity, while the UV laser keeps the transparency intact, with perfectly legible white marking.

In the case of marking a 3×3 mm Datamatrix on a CR-39 lens, the UV laser is the only technically feasible option. With optimized parameters (speed 600 mm/s, frequency 30 kHz, power 80%, defocus +2 mm), a grade A marking according to ISO/IEC 15415 is achieved, with high contrast and zero impact on the optical properties of the lens.

Decision criteria for choosing the system

The final decision between UV laser and CO₂ must take into account a few key elements. First, the material portfolio must be evaluated: if 80 percent of production involves opaque acetate and traditional technical plastics, CO₂ is a rational choice. If, on the other hand, you work mainly with polycarbonate, ophthalmic lenses, or transparent frames, UV laser becomes necessary.

Second, regulatory and quality requirements must be considered. If the end customer requires compliance with stringent traceability standards (as in the case of medical devices or products destined for regulated markets), the UV laser’s ability to generate very high resolution codes becomes a decisive competitive advantage.

Finally, it is necessary to think in terms of the complete process: integration with vision systems for quality control, the need to work on complex geometries, and the flexibility required to handle small batches of different products are all factors that can steer the choice toward one technology over the other.

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Why 9.3 µm instead of 10.6 µm?

The difference between the two CO₂ lasers lies in the wavelength of the emitted infrared radiation. The standard CO₂ laser works at 10.6 µm, while the 9.3 µm CO₂ laser exploits a different vibrational transition of the CO₂ molecule. From a practical point of view, the main effect is the minimum achievable laser spot size and, consequently, the fineness of the etched line.

With the 9.3 µm laser, the spot is inherently smaller for the same optical configuration, allowing finer lines and finer details to be drawn. This translates into better definition of alphanumeric characters, logos, and decorative markings-a key issue when working on high-end frames, where the branding must be legible, sharp, and unobtrusive without being obtrusive or coarse.

Materials involved

In eyewear, the most common plastic materials are:

• Cellulose acetate: used for mid- to high-end frames; offers good workability and aesthetic flexibility.
• Polycarbonate: mainly used for sports frames and lenses; lightweight and impact resistant.
• Other polymers: nylon, TR90, grilamid, less frequent but present in specific niches.

All these materials absorb CO₂ radiation well, but the aesthetic quality of the marking depends strictly on the precision of the laser spot. The 9.3 µm laser, due to its shorter wavelength, concentrates energy on a smaller area, reducing the diffuse thermal effect and improving the sharpness of the mark.

Concrete applications in the eyewear industry

Model code and size marking

Each frame bears, usually on the inside of the rod, a set of information: brand name, model, size (gauge-bridge-rod), and color code. These characters must be legible but at the same time unobtrusive. With the 9.3 µm laser, it is possible to mark alphanumeric characters with a height of 1.5-2 mm while maintaining excellent legibility, without excessive burning or smearing that would compromise the aesthetics of the product.

Marking of logos and trademarks

Luxury brands require faithful logo reproduction even on curved or small surfaces. The finer stroke of the 9.3-µm laser allows complex details-such as fine graces, decorative elements or serifs-to be reproduced without loss of definition. This is especially important for brands that focus on visual identity and brand consistency on every component of the frame.

Custom decorations and patterns

Some handcrafted or high-end eyewear manufacturers offer the option of customizing temples with decorative engravings, customer initials or geometric patterns. The 9.3-µm laser allows for continuous lines, smooth curves and sharp transitions without the risk of excessive charring or dull areas around the engraved line.

2D code marking for internal traceability

In some cases, especially in industrial production settings, a Datamatrix marking of a small size (4×4 mm or less) is required for lot or individual part traceability. Again, the laser spot accuracy of 9.3 µm helps to achieve well-defined code forms, improving the read rate and reducing the risk of errors during automatic verification.

Why is the 30 W used almost exclusively?

In the eyewear industry, the most popular laser power is 30 W. This is because:

• Adequate speed: A 30 W laser enables the marking of characters and logos in times compatible with medium-to-high production cycles (up to several hundred frames per day), without compromising on quality.
• Thermal control: higher powers (50 W or more) would increase speed, but make control of the thermal effect more critical, with risk of surface deformation or localized burns, especially on thin materials such as acetate rods.
• Balance between cost and performance: the 30 W represents a technical balance point, allowing for a fine, clean stroke without the need for extreme operating frequencies or complex cooling systems.

Lower powers (e.g., 10 W or 20 W) can be used for very limited machining or small-scale craft applications, but are not sufficient to ensure acceptable cycle times in structured production settings.

Typical process parameters

Without going into too much technical detail, the parameters of marking on cellulose acetate with 30 W 9.3 µm CO₂ laser generally settle on:

• Pulse repetition frequency: 5-20 kHz, depending on the detail required.
• Scanning speed: 200-800 mm/s, depending on the desired engraving depth.
• Effective power: 10-30% of rated power, modulated to avoid excessive carbonization.
• Number of passes: usually 1, rarely 2, to keep the aesthetic effect clean.

On polycarbonate, the parameters are similar, but with special attention to heat management to avoid thermal stress phenomena that could cause micro-cracking.

Comparison with other laser technologies

Fiber laser

Fiber lasers (1064 nm) are very effective on metals, but on non-additive plastics they tend to leave poorly contrasted marks or require specific additives. In the eyewear industry, where aesthetic materials are worked on and the polymer compound cannot always be modified, the CO₂ laser remains the dominant choice.

Laser UV

The UV laser (355 nm) offers “cold” marking with a photochemical effect, which is particularly suitable for heat-sensitive plastics. However, for applications on acetate and polycarbonate in the context of eyewear, the 9.3-µm CO₂ laser provides a good compromise between quality, speed, and material handling, without the need to invest in more expensive UV sources with shorter lifetimes.

Critical issues to consider

Geometric tolerances

Mount rods can have varying curvatures and thicknesses. It is important that the marking system include a motorized Z-axis to compensate for height variations and keep the laser spot in focus at all times. Some systems also integrate a laser autofocus system to verify the correct focal distance in real time.

Smoke management

Laser marking on cellulose acetate generates fumes containing organic derivatives. An effective vacuum system, possibly with activated carbon and HEPA filters, is essential to keep the focusing optics clean and ensure a healthy working environment.

Centering the marking

To ensure that logos and codes are positioned correctly on the rod, it is advisable to use loading jigs or, alternatively, vision systems that automatically detect the position of the part and adjust the marking layout accordingly.

Inline integration or stand-alone station?

In the eyewear industry, laser marking is often performed on a stand-alone station, with manual or semi-automatic loading. In more structured production settings, the laser can be integrated into the line after the assembly and polishing stages, with belt or pallet transport systems and automatic loading/unloading. In either case, the flexibility of the 9.3-µm CO₂ laser allows it to adapt to variable production volumes and even small batches, without the need for complex reconfiguration.

Conclusions

The choice of the 9.3-µm CO₂ laser in the eyewear industry is not accidental, but meets precise requirements for aesthetic quality, line definition and thermal control on delicate plastics. Compared to the conventional 10.6-µm CO₂ laser, the shorter wavelength allows for a finer spot, resulting in sharp, discreet markings that meet the aesthetic standards required by high-end brands.

The 30 W power is the optimal balance point for balancing marking speed and result quality, allowing it to work effectively on cellulose acetate, polycarbonate and other polymers without compromising material integrity. Whether it is for pattern codes, logos, decorations or 2D codes for traceability, the 9.3 µm CO₂ laser proves to be the technology of choice for an industry that does not allow compromises on the precision and aesthetics of the finished product.

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The Industry Challenge

The needs of the eyewear market are constantly evolving. Simple marking is no longer sufficient: manufacturers are demanding micrometric precision, versatility on materials and flawless aesthetic results. Traditional laser systems, while having served the industry well for years, are showing increasing limitations, especially in handling the heat affected zone (HAZ) and processing innovative materials. On fine acetates or titanium alloys, even the slightest thermal alteration can compromise the value of a high-end product.

Technological Evolution: from CO2 to Picosecond

The evolution of laser technologies in the industry can be summarized in three generations:

First Generation: CO2 Laser

• Strengths: simplicity, low cost, excellent on organic materials
• Limitations: limited accuracy, large thermally altered zone, unsuitable for metals
• Typical applications: marking on standard acetates, packaging

Second Generation: UV Laser

• Strengths: higher precision, good quality on plastics
• Limitations: high cost, frequent maintenance, limited power
• Typical applications: precision markings on engineering plastics

New Generation: Picosecond Laser

Picosecond technology represents a generational leap, overcoming the limitations of previous technologies through a radically different approach to laser-material interaction. With pulses a thousand times shorter than conventional lasers (10^-12 seconds), picosecond radically changes the interaction between laser and material: energy is released so rapidly that the material undergoes a cold ablation process, where molecules are removed before heat can spread to surrounding areas. This allows:

• Accuracy greater than 25 microns (versus >100 microns for CO2)
• Near-perfect thermal control with virtually nonexistent HAZ
• Versatility on all materials, from metals to the most delicate plastics
• Controlled color changing effects impossible with other technologies

Practical Applications

In the context of eyewear, picosecond technology demonstrates its versatility in multiple applications:

• On titanium components, makes high-contrast markings while fully preserving mechanical properties
• On acetate frames, it ensures definitions above 25 microns without micro-fractures
• On polycarbonate lenses, allows functional and decorative markings without surface alteration

The LASIT Experience

LASIT has developed a comprehensive technology ecosystem around picosecond technology, with more than 100 systems implemented in the past two years. At the heart of this ecosystem is FlyCAD, the proprietary software that represents the intelligence of the marking system. FlyCAD integrates:

• Advanced algorithms for parameter optimization
• Management of complex logos and gradients
• Industrial traceability systems 4.0
• Real-time process control

Integration of picosecond systems requires multidisciplinary expertise, which LASIT has developed in-house. Synchronization between laser source, motion systems, and control software is managed through proprietary protocols that ensure optimal performance. The choice of 25- and 50-watt powers, combined with IPG sources, is the result of careful optimization of the entire system.

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In the Italian eyewear scene, OMAS represents a manufacturing reality of excellence with nearly 60 years of experience in creating high-quality frames. The company, based in Segusino (TV), has been able to combine traditional craftsmanship and technological innovation, continuously investing in updating its production processes to ensure maximum quality and precision.

The challenge: ensuring precision and quality in the luxury segment

In the eyewear industry, especially in the luxury segment in which OMAS operates, precision marking of components is a crucial element. It is not just a matter of affixing a logo or identification code, but of making perfect engravings that enhance the product and ensure its traceability, while maintaining high quality standards.

The company, led by CEO Liana Minute and with Andrea Massani representing the new generation and future of the company, faced the challenge of constantly improving marking processes, looking for solutions that could guarantee flawless results on different materials and complex geometries typical of eyeglass frames.

LASIT’s solution: a path of technological partnership

The relationship between OMAS and LASIT is not a simple customer-supplier relationship, but a true technological partnership developed over the years. OMAS began its journey with LASIT by initially purchasing a CO₂ laser system, ideal for specific applications in eyewear.

As production needs evolved and the range of materials processed expanded, the company subsequently integrated a second laser system, this time with picosecond technology, which is particularly suitable for high-precision processing of delicate materials used in the fashion industry.

“The flexibility and efficiency of LASIT’s systems have been an added value to our production, allowing us to achieve superior quality markings on different types of frames,” explains Andrea Massani.

The latest evolution: CompactMark G8 with picosecond laser

OMAS’ latest acquisition, the CompactMark G8 with 50W picosecond laser technology, represents another step forward in the company’s innovation journey. This machine, designed specifically for applications that require extreme precision, is distinguished by its rugged all-welded, stretched and milled steel construction with ground guideways and recirculating ball screws.

The CompactMark G8 is equipped with 3 positioning axes (XYZ axes) that allow for extremely precise and repeatable markings. The worktable measures 800x450mm and is made of ground, hard-anodized aluminum, with a 50x50mm pitch hole matrix that allows you to create quick placements with dowels or attach equipment with M6 screws.

The advantages of picosecond lasers for eyewear

Picosecond laser technology is an ideal solution for the eyewear industry for several reasons:

• Extreme precision: due to the very short pulse duration (in the order of picoseconds), the laser allows for extremely detailed and precise engravings, which are essential for small components typical of eyewear
• Minimization of thermal effect: the ultra-short pulse dramatically reduces heat transfer to the material, preventing unwanted deformation or alteration in the areas surrounding the marking area
• Versatility on different materials: the technology is effective on a wide range of materials used in eyewear, from metal to acetate, plastics to composite materials
• Superior aesthetic quality: markings appear sharp, defined, and with optimal contrast, a key aspect for visible components in luxury products

“The marking quality we achieve with the LASIT picosecond system fully meets the precision and finishing requirements demanded by our most demanding customers in the luxury eyewear industry,” Liana Minute emphasizes.

Results and benefits

The implementation of LASIT systems, culminating in the acquisition of CompactMark G8, has brought numerous benefits to OMAS:

• Increased productivity: the machine allows marking a large area (700x450mm), ideal for both single components and pallets with hundreds of small parts
• Production flexibility: the versatility of the system allows rapid switching between different types of processing, reducing setup time and increasing overall efficiency
• Consistent quality: the machine’s stable and robust design ensures consistent and repeatable results, which are essential for maintaining high quality standards
• Waste reduction: the accuracy of the system minimizes marking errors, significantly reducing production waste
• Expansion of production capacity: the new machine has enabled OMAS to expand its offerings, accepting orders that require particularly complex processing

An investment for the future

For OMAS, the acquisition of the third LASIT machine represents not only a response to immediate production needs, but a strategic investment for the company’s future.

“In a sector as competitive as luxury eyewear, the ability to offer innovative solutions of the highest quality is a key distinguishing feature,” comments Andrea Massani. “The partnership with LASIT has enabled us to further raise our production standards, confirming our position of excellence in the market.”

The history of OMAS and LASIT shows how technological innovation, when guided by a clear vision and supported by a reliable partner, can be a decisive factor in a company’s success, even in a traditional industry such as eyewear.

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