What Is Lens Finishing?
Along with surfacing and lens coating, lens finishing is an essential process in the production of eyeglasses, typically performed by wholesale optical labs. This process involves cutting eyeglass lenses to fit specific frames, whether they are standard, rimless, or three-piece mounts. Initially, lenses are usually round and about 70mm in diameter before being precisely shaped to match a frame's unique contours.
The Role of Edging Equipment in Lens Finishing
Edging, a critical part of the lens-finishing process, involves the use of specialized equipment to tailor lenses to specific requirements. Two primary types of edgers are used:
Wet Edgers: Traditional tools that grind lenses using diamond-impregnated wheels, coupled with water to remove debris and prevent heat damage. These edgers often incorporate drill functions for additional precision.
Dry - Robotic Edgers: The modern choice in lens edging, these edgers use CNC tooling for greater control over bevel design and placement. They can freely move in all directions, offering flexibility and precision.
The Variety of Edges Produced
Lenses are finished to match various frame designs, each requiring a different edge type:
- Full-Eyewire Frames: These frames, where lenses are completely surrounded by material, use a V-shaped bevel for retention.
- Semi-Rimless Frames: In these designs, the lens edge is ground flat and grooved for nylon cord seating.
- Fully Rimless Frames: These require a perfectly flat, smooth edge.
Measurement capture for these frames varies, with machines using different methods like tracing the frame bezel or capturing the outside circumference of the lens.
Timeframe of the Lens Finishing Process
The duration of the finishing process depends on the lens material and frame type. Preparatory steps such as lensmeter work and protecting AR coatings take a few minutes. The actual edging can range from three minutes for simple lenses to up to seven minutes for more complex jobs, like high-index lenses in drill mounts.
Steps in the Finishing Process
The finishing process ensures that the lens aligns correctly in front of the wearer's eye. This involves:
- Marking: Adjusting the lens to position its optical center or other reference points precisely in front of the pupil.
- Blocking: Attaching the lens to a block using an adhesive pad to hold it securely during edging.
- Edging: Placing the blocked lens in the edger and making setting the appropriate parameters, so the edger can cut the lens.
- Assembly: Fitting the lens into the frame.
Advanced edgers can even add artistic elements to lenses, such as high-luster polishes or etchings.
The Importance of Operator Skill
While most modern edging is automated, the operator's experience is crucial for handling complex prescriptions and mounting styles. An experienced operator can adjust for inconsistencies, ensuring optimal lens placement and minimizing costly mistakes.
Final Assembly: More Than Just Edging
After edging, the lenses are assembled into the frames. This requires skill, especially with older or unique frames. Adjustments and minor repairs are often made during this stage to ensure perfect fit and alignment.
The Significance of Edger Capabilities
The capabilities of the edger are vital for accommodating various lens powers and frame styles. Accurate tracing and precise bevel placement are key to successful lens fitting, particularly in complex prescriptions.
In summary, lens finishing is a detailed and skilled process that transforms raw lens blanks into precisely shaped lenses to fit a wide range of frames. It requires a combination of advanced equipment and skilled operators to ensure that each pair of glasses meets the highest standards of quality and comfort.