5 September 2008

Laser Welding Pyrex Pipettes

Synrad's sealed CO2 lasers are used in a variety of industrial processes including cutting, welding, drilling, and marking.

Pyrex® is a tough, durable, low-expansion borosilicate glass widely used in the manufacture of pipettes, flasks, and other Pyrex glassware found in laboratories throughout the world.
This unique application calls for sealing Pyrex glass pipettes by welding one end. Welding glass (or metal) is an ideal CO2 laser application because the laser provides an excellent pin-point heat source capable of generating millions of watts per square centimetre depending on laser output power and focused spot size.

The glass welding set-up consists of a rotary stage suspended beneath a gas jet manifold affixed to the laser faceplate. The manifold holds a 63.5 mm (2.5”) positive-meniscus focusing lens that provides a 100-micron (0.004”) spot with a 1.8 mm (0.07”) depth of field. A gas jet fitting below the optic provides a connection for the assist gas, which in this case is 0.07 bar (1 PSI) of clean, dry air.

Each pipette has an outside diameter of 2.1 mm (0.0825”) with a wall thickness of 0.25 mm (0.01”) and is spun at 330 revolutions per minute by the rotary stage. After firing 50 watts of power at the end of the pipette for approximately 10 revolutions (1.8 seconds), perfectly welded spherical ends were achieved on the Pyrex pipettes.

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