Shree is the leading Lens blocking alloys manufacturer, Suppliers and distributors in India and used to blocking optical lens blanks to surfacing for grinding the required optical size into the lens blank. The advantage of using our low melting temperature alloys with our cover flux is easy to use, with more reliable 20% life of alloys and recyclable. Cover flux also maintained the temp of alloys bath.
USES OF LENS BLOCKING ALLOYS
Plastic lenses
The low melting temperature alloy used for plastic lenses is alloy LB 4747, with a melting temperature of 117°F(47°C). Due to the popularity of plastic lens, it is the most common alloy for lens blocking and can also be used for glass lenses. if a higher temperature alloy is used it can be damage the lenses .
In LB7070 with a melting temperature of 158°F(70°C), is another commonly used alloy. However it has a better bond strength and is used only for glass lenses.
Shree Manufacturing have a variety of lens blocking cadmium and lead free alloys which is non hazardous for environment and human body which can be used for glass as well as plastic lenses. These offer the advantage of reduced environmental and health concerns
Lens blocking
A protective plastic tape is placed over the lens blank prior to mounting the lens blank and surfacing block into the blocker. The blocker contains the molten alloy (approximately 5°F above the liquids temperature of the alloy) until it is forced, by air pressure or manual hand pump, between the tape on the lens blank and surfacing block. The alloy is cooled until it solidifies and bonds the lens blank tape to the surfacing block. The surfacing block is then mounted in a chuck and is used to protect the lens during the grinding operation. After the grinding operation, plastic lenses are removed from the surfacing block by the inertia of knocking the surfacing block on a solid surface. Glass lenses are removed by dipping them into a hot water bath. When the alloy melts and the lens is separated from the surfacing block, the alloy settles to the bottom and is recovered by draining it through a valve.
