CL Manufacturing Flashcards
1
Q
SCL methods
A
- lathe cutting
- spin casting
- cast mould
2
Q
Combination methods
A
- moulding + lathing
- spin casting + lathing
3
Q
What is lathe cutting
A
- Anhydrous button is lathed in a controlled atmosphere
- button mounted on a spinning shaft, and shaped with a computer cutting tool
- lens is then removed and hydrated to soften it, and then sealed in saline
- autoclaved at 121 degrees for 15 mins
4
Q
Lathe cutting advantages
A
- few limitations of Rx
- established for CL manufacturing
- easily adapted for CL manufacturing
- reserved for customer extreme ranges
- suitable for most materials
5
Q
Lathe cutting disadvantages
A
- increased cost
- time consuming
- variable surface finish
- strict humidity control
- cleaning/polishing required
- lenses must be soaked
6
Q
What is spin casting
A
- liquid monomers poured into mould
- mould is spun in controlled environment
- rotation velocity/surface tension/gravity defines the back curvature (BVP)
- mould shape defines front surface
- UV light applied to polymerase monomers
- edges then buffed and polished
- lens hydrated
7
Q
Spin casting advantages
A
- very smooth back surface
- back surface matches corneal profile
- least likely to produce surface defects
8
Q
Spin casting disadvantages
A
- slower and more complex
- more expensive
- not as scalable as moulding
- requires polishing
9
Q
What is injection moulding (cast mould)
A
- monomers injected into cast a high pressure
- UV light or heat initiates polymerisation, then lenses removed
- lenses are then hydrated to soften
- lenses are verified, packaged and sterilised in same way as spin casting
10
Q
Injection moulding advantages
A
- very quick
- low costs
- easy to produce
- many lenses at once
- most widely used
11
Q
Injection moulding disadvantages
A
- strict environmental control
- expensive equipment
- number of moulds limits parameters
12
Q
RGP manufacturing
A
- lathe cutting
- cast moulding
13
Q
RGP lathe cutting
A
- similar to SCL
- reduced margin of error
- separately configured lathes for front and back surface
- engraving/marking is common on RGP lenses stored dry
14
Q
RGP cast moulding
A
- Similar to soft lens material
- lens left to dry
- mould broken apart and lens revealed
15
Q
Toric manufacturing
A
- dual axis lathing on stationary lens
- can produce any shape
- blank lens is crimpled across the front surface, then worked into a sphere, releasing the crimpling leaving a toric surface
- moulding requires a separate mould for each Rx
- dual axis flying cutter, the cutter set to particular axis as this passes by the rotating lens button it creates the toric shape
