Edging Flashcards
What are the 8 steps to the edging process?
1-Setting the edger size
2-Setting parameters and specifications
3-Marking edger dials
4-Chucking lenses
5-Determining bevel placement
6-Cutting
7-Checking sizing accuracy
8-Mounting
What is pattern making?
The process of making an object that matches the shape of a lens in a frame which be used as a guide to edge uncut lenses.
When does the pattern making process occur?
Takes place after surfacing, coating, and centration.
What are 5 advantages of a frame tracer?
-determines size and shapeconsistently
-Traces frame in three, instead of two dimensions
-Works with an edger to demonstrate what the placement of the bevel will look like at any given point on a lens
-Trace a shape from an old lens or coquille
-Transfer data to a surfacing laboratory to help determine how thin a lens may be surfaced
What are 4 disadvantages of a frame tracer
-plastic frame may not retain the same shape it had with the demonstration lens in place
-may change the shape of the eyewire as they trace as the tracer exerts force
-Remotely traced frames may not exactly match the old lens
-are unable to trace frames with narrow B dimensions
What is chucking?
a method of keeping a lens in a certain position relative to the rotational/geometric center of a shape in order to accurately shape a lens for a given frame
What are the three types of chucking?
Manual
Air
Electric
Explain Manual Chucking 2
-clamped firmly but not with excessive pressure
-then handle locked in place
Explain Air Chucking 2
-lens holding assembly is connected to a air line and compressor which applies clamping force
-also known as pneumatic chucking
Explain Electric Chucking 2
-Drive motor presses the lens holding assembly together to hold the lens in place
-pressure can be controlled depending on the material
What consideration should we make when chucking a polycarbonate material? 2
-softer material
-ensure all surfaces that the lens touches are free from rough edges or burrs
What considerations should we make when chucking an antireflection-coated lens?
-microcracks/crazing can occur on lens surface due to heat, pressure, and flexure
What considerations should we make when chucking an laminated lens?
specialized wheel is required
What is a roughing wheel?
A coarse diamond wheel which cuts a lens down to rough
size rapidly.
What is a finshing wheel?
Finer diamond wheel brings lens to size and incorporates
required bevel.
What do we consider when edging crown glass in regards to the wheels?
Requires a different roughing wheel specific for
glass
What do we consider when edging photochromatic glass in regards to the wheels?
Treated almost the same as crown glass but due to the heat it produces during edging, it is harder on
wheels and may require specially designed wheels
What do we consider when edging high index glass in regards to the wheels?
-Should be edged with less pressure than
standard crown glass
What do we consider when edging CR39 Plastics in regards to the wheels? 2
-Same roughing wheels that cut glass can be used
-wheels require dressing as plastic particles clog spaces
between abrasive surfaces
What do we consider when edging High-Index Plastic in regards to the wheels? 2
-Edged in the same manner as CR39
-can emit a non-hazardous sulfurous odor - ventilation
recommended
What are the 3 main bevel types?
V-bevel
Hide-a-bevel
Mini-bevel
What is a V-bevel? 2
-groove apex in the middle of the lens
-rarely used today
What is a hide-a-bevel?
A flat or sightly angled edge either in front of or behind the
bevel of a lens
What is a mini bevel?
A hide-a-bevel with an angled ledge
What are 3 different edge types?
Facet
Rolled
Polished
Explain a facet edge type. 2
-Used with rimless, grooved, and thin metal frames
-resembles beveled edge but with a relatively steep bevel
cut onto the front or back edge, then highly polished
Explain a rolled edge type.
Reduces minus lens edge thickness by rounding the back
surface edge of a lens
Explain a polished edge type
Gives the lens an especially smooth appearance
What is pin beveling?
Pin bevelling smooths out the bevel.
What are the reasons pin bevelling is used?
Breakage prevention
Cosmetic considerations
Wearers safety
