I have seen way too many poly lenses chip around the edges in grooved rimless.Is this because my local lab grooves the lens after the backside hard cote is applied? If so, then would Opticotes Poly seal prevent this chipping?
I have seen way too many poly lenses chip around the edges in grooved rimless.Is this because my local lab grooves the lens after the backside hard cote is applied? If so, then would Opticotes Poly seal prevent this chipping?
Sounds more like a dull grooving wheel
It's either the grooving wheel, or they're not making the groove wide and deep enough to properly fit the line into. If they make a shallow, narrow groove, they have to "smush" the line into it so it's not sticking out around the edge, and over time this will cause the stress cracks. It could also be those horrid groove frames that have no plastic line lining at the top (the figure 8 lining), so the lens is mounted directly into metal. They need to make sure the groove is wide and deep enough to accommodate this, with no stress, before they send it out.
Backside hard coats are generally applied to an uncut lens in the surfacing dept., and plays no role in whether or not the lens develops stress cracks after edging.
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question for lab managers.... ( 1 2) jb@kso
Our office is having the same problem, from two different labs in two different states. Poly grooved Rimless with tons of chipping and large stress cracks after just a couple of weeks or months of wear. No one seems to know why. We are starting to go with trivex when possible to minimize this.
~ Erin
ABOC
I'm gonna go with a dull edging or grooving surface.
#1 Reason for grooved edges chiping: Edges made too thin not allowing each edge to have enough strenght .
#2 Reason for grooved edges chiping: Trying to alighn temple or chassis with lens in the frame or without enough support given to chassis when raising or lowering temple.
#3 Frame gets dropped and puts impact on edge of frame, especially of those with metal instead of plastic interliner.
#4 Too much tension on lens from nylon chord, and or chassis.
#5 Groove not deep enough, lens will have a tendancy to slip out, with each slip lens can become chipped when it twist in frame or hits the floor.
6) Nylon chord is too wide for groove.
7) Idiot dispenser is unwilling to cut (because he doesn't know how to replace) chord to remove lenses for replacement or adjustment.
8) Lens either warps from time an heat and will not fit chassis part of frame any more.
9) Chassis is wrong shape (and should be hand formed) to curve of groove at top of lens.
Many labs and many practioners concider "thinness" to be the most important part of dispensing "quality" work. When this is over-done, especially on plus lenses, the edges chip. Maybe not from lab to dispenser, sometimes not from dispenser to patient, but sooner or later.
Doesn't really matter too much what material is used.
Chip
Duh!
Last edited by chip anderson; 05-30-2009 at 11:00 AM. Reason: 7,8.&9
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