Define surfacing
The process of creating the prescribed refractive power, prism , and major reference point (AKA PRP) location on a lens by generating the required curves and bringing the surface to a polished state.
What is the purpose of the surfacing process?
- generates (cuts or grinds) the curves that gives the lens power, prism, and it’s PRP location.
- smooth and polishes the power curves to a transparent-like clarity.
- creates the general size (diameter) and thickness of a lens.
What are the two major methods of surfacing ?
Conventional and digital
What happens during the conventional method of surfacing ?
- front surface is fully molded with base curve, channel, addition, and etchings completed.
- the distance prescription is ground into the back surface of the lens blanks.
- lenses need to be fined and polished with identically shaped lap toll surface for each lens.
What happens during the digital method of surfacing?
- a diamond point lathe cutter, cuts the prescription into the back and/or front surfaces of a semi-finished lens blank.
- no fining stage is necessary.
- uses a soft lap polishing tool to smooth out the lens surface.
- a laser can be used to etch progressive markings onto the lenses.
- can integrate other measurements such as near PD, pantoscopic tilt, face form wrap, and vertex distance.
Wavefront technology
Designed to correct higher-order aberrations, provide sharper vision than regular lenses, help wearers see better in low light conditions, and experience improved contrast and color vision.
Freeform
Effectively “optimized” because they can be precisely generated to a power of 0.01D.
What happens during the surfacing lab?
- processes a semi-finished lens blank by completing the generation stages
- also can complete the finishing process
Also called : full service lab, fabrication lab, production lab
What happens during the finishing lab?
- processes finished lens blanks and uncut lenses by completing the edging
- assembles spectacles
- cleans and performs final quality inspection
What happens during the lens choice stage ?
The semi-finished lens is chosen.
What happens during the calculation stage ?
Information is inserted into the computer.
- patient info
- frame info
- lens info
Patient info in the lab calculation stage include:
Rx
PD
Fitting Height
Frame info in the lab calculation stage include:
Design and size
Lens info in the lab calculation stage include:
Design Material BC Size Blank thickness
Computer info dataflow chart
Computer information dataflow chart
What happens during the layout and blocking stage ?
Layout: movement or orientation of a lens in preparation for a cutting procedure.
Blocking: process of adhering the surface block to the lens blank.
What happens during the generation stage ? ( 3 main functions)
- it cuts and grind the power curves (F2) into the back surface of the lens blank.
- reduces the thickness of the lens by removing the majority of the material.
- reduces the overall diameter of the lens through cribbing.
What happens during the fining stage ?
Smooth the back surface after generation stage. WET SANDING.
The cylinder machine is used to do this.
A lap tool with an attached fining pad.
What’s the cylinder machines task ?
To smooth the back surface
What is a lap tool?
A block of metal, plastic, or styrofoam that exhibits convex curves on the top.
What is a fining pad ?
Flower shaped portion of sandpaper that is mounted on the lap tool
What happens during the polishing stage ?
Brings the lens back to a clear stage and restores clarity.
Use of a smoother fuzzy polish pad and lens polish.
What happens during de-blocking and cleaning stage?
Surface block and surface saver tape and removed from the front of the lens.
Cleaned with isopropyl alcohol to remove block bonding material.
