Rimless frames are engineered through precision mounting systems that attach the bridge and temples directly to the lenses鈥攏o surrounding frame material. The engineering challenge is balancing invisibility with structural security.馃敥
Core Mounting MethodsScrew-Mounted (Traditional Drill Mount)The most common approach. Two or more through-bores are drilled into the lens edge area. The bridge and end pieces have barbed metal pins or threaded posts that pass through these holes, secured with screws and nuts or compression bushings .
A patent describes using a plastic filament (nylon) through auxiliary holes to invisibly anchor the bridge and temple elements, keeping hardware hidden .Compression/Clamp MountingA newer approach that avoids drilling entirely. The bridge and end pieces have protrusions that clamp onto the lens surface. The fixing body is lowered over the lens and fastened with a nut, creating a pressure seal . This prevents lens cracking from shock and extends lens life by eliminating holes as stress points.
Groove-Mounted (Rimway/Cortland Style)A groove is cut around the lens edge. A support line (often fishing line or nylon) sits in the groove and threads through holes in the bridge and end pieces . This provides stability while keeping the attachment nearly invisible.馃搻 Engineering the Drill HolesDrilling rimless lenses requires precision to avoid star cracks or flaking:路 Hole angle: The system must account for the surface curve of the demo lens versus the actual prescribed lens. A software method selects drilling angles鈥攏ormal to the demo lens, normal to the actual lens, or arbitrarily set鈥攁nd calculates hole position data to compensate for curvature differences .路
Material selection: Trivex is preferred for drilled rimless because it is least affected by drilling, reducing star cracks. Its tensile strength allows thinner edges without chipping . Polycarbonate is also recommended for safety .路 Edge thickness: A minimum of 2.0 to 2.2 mm edge thickness is maintained for groove-mount rimless. High-index lenses with thinner edges (1.8 mm) flake during fabrication or later .馃敡 Structural Stability SystemsTo prevent lenses from rotating or shifting, engineers add:路 Anti-rotation features: Non-cylindrical pins (oval, square) prevent relative rotation between lens and mount .路 Three-point fit: Nose pads and temples create tripod stability, keeping lenses aligned .路 Spring hinges: Integrated spring mechanisms allow temples to flex without breaking the mount .鈿狅笍
Trade-OffsRimless frames are lightest and most invisible but least durable. The mounting points are stress concentrators鈥攍oose screws cause lens shift, affecting vision and risking cracks . They require more frequent professional checks of mounting hardware .Would you like to explore specific mounting hardware designs, or how drilling parameters are calculated for different lens curvatures?