CO2 LASER used in industry
LASER- light amplification stimulated emission radiation, that generate an intense beam of coherent monochromatic light . carbon dioxide laser are capable of generating tremendous heat intensity.
This laser operate in infrared, mirrors are silvered, while windows and lenses are made of either germanium or zinc selenide (znse).
for high power amplification gold mirror and zinc selenide window and lenses are preferred. because laser beam strike the mirror and reflect and go towards lens. mirror is adjustable to 45 degree.
CUTTING PARAMETER- laser power (50 watt to 3500 watt. co2 laser power below 200 watt for non metal and above 5000 watt used for welding or heat treatment),
-cutting speed,
-cutting gas pressure (pressure is set between 1 and 5 bar when oxygen gas is used as cutting gas, for thick material -low pressure +1,-1 bar are used and thin material- high pressure +5,-5 bar),nitrogen gas is used for cutting stainless steel or aluminium at pressure up to 20 bar ,standoff distance between nozzle and material(sheet)
Carbon dioxide laser MIRROR , LENSES , WINDOW,CERAMIC AND NOZZLE are used
laser cutting system combine the heat of focused beam with assist gas, which is introduced through nozzle coaxial to focused beam .
NOZZLE is integrated with focusing assembly below the lens in order to develop the desired gas assist, misalignment of nozzle normally cause noticeable variation in cut quality with respect to direction of cutting traverse.
- some industry also used CERAMIC above the nozzle because gases heat that blow out from nozzle, some of them are reflect back then ceramic isolate the heat and mainly used for safety purpose, above ceramic lens is placed.
MECHANISM OF LASER CUTTING- melting-shearing(melting), vaporisation(boiling), chemical degradation(burning).
PVC NEVER CUT BY LASER.- it emit pure chlorine gas when cut and ruin the optics and cause the metal of machine to corrode.
COMPONENTS USED IN CO2 LASER -1. ZNSE MENISCUS LENS- used to achieve the highest possible power density when cutting with co2 laser.
2. ZNSE PLANO-CONVEX LENSES- is used when diameter of focal point is not clear.
3. PARTIAL REFLECTOR AND END REFLECTORS MIRROR- they both determine the optical quality of laser resonator and are used to create and control the laser energy on the workpiece.
4. when we see LENS S1 and S2 are written, that means SIDE 1 AND SIDE 2. in industry mainly mirror are represent by S1-PO( SIDE 1-PLANO), S1-5MCC(SIDE 1- RADIUS 5M CONCAVE), S1-10MCX( SIDE 1 -RADIUS 10 M CONVEX). coating determine the ratio between reflected and transmitted output. one side of lens is coated with partial reflective and other side with an anti reflective(AR) coating.
5.REFLECTOR- reflector inside the co2 laser are designed differently -
TRZ- (total zero phase shift total reflector)- the quality of CO2 laser beam cutter is highly dependent on defined polarisation of laser beam along whole beam control optics
ATFR REFLECTOR ( absorbing thin film reflector) are used to avoid reflection caused by reflective metal for example copper, aluminum,brass etc.
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