laser basics welding

8/11/2019 Laser Basics Welding

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LASER BEAM WELDING AND CUTTING


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Laser & EB Welding

Wide & partial fusion Narrow & deep fusion

Conventional welding

Why LASER ?


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INCANDESCENT Vs. LASER LIGHT

LASER WELDING


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S


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CHARECTERISTICS OF LASERS Common light : incoherent & varied lengths in different directions

Laser Beam is a coherent light waves are identical & parallel

Temporal coherenceHow long a wave train is continuous?

Ordinary light ~ few tens of microns

Lasers ~ from 20 cm to few tens of mt

DIRECTIONALITY

It is the spread of the beam when its travels

Divergence is of the order of 1 milliradian

i.e , when the beam travels for 1m, the beam diameterincreases by 1mm .

.


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Semi conductor lasers : Laser diodes

Gas lasers : He- Ne, CO 2 Chemical Lasers : Hydrogen FluorideLiquid lasers : Organic dye

Excimer lasers : Rare gas mixturesSolid state lasers : Nd:YAG , Ruby

LASER SYSTEMS


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LASERS FOR MATERIAL PROCESSING

Gas lasers : up to 45kwatt

Solid state lasers:up to 4kwatt

Semiconductor lasers: up to 40watt

CW lasers welding, cutting & surface modificati

Pulsed lasers drilling & welding

Circular and linear beams


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E1

E 1

E1

E2

E 2

E1

E1

E1

E2

E2

E2

Stimulated absorption

Spontaneous emission

Stimulated emission

Energy-state transition diagram

E2

Initial state Final state


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CO2 Laser Theory


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Total Lasing (Light Amplification)


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Laser medium Laser output

Excitationsource

Mirror(100% reflective )

Mirror(partially transparent )

Generation of laser beam


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CO 2 Laser principle


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Concentrating light waves into narrowly defined highly intense beam that impart

tremendous energy on a small area to produce fusion


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CARBON DIOXIDE LASERS

CO 2 : Lasing gas, 1-9% of the gas mixture

N2 : Efficient excitation of CO 2 molecules,10-55% of the gas mixture

He : For conducting heat out of resonatorand emptying the lower CO 2

energy level, balance of gas mixture


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In ICF , MS 20 , SS 15 & AL 11 MM


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Laser cutting is a technology that uses a laser to cutmaterials, which is used in the production line and istypically used for industrial manufacturing

applications.Laser cutting works by directing the output of a highpower laser, by computer, at the material to be cut.The material then either melts, burns, vaporizes away,or is blown away by a jet of gas, leaving an edge witha high quality surface finish. Industrial laser cutters areused to cut flat-sheet material as well as structural andpiping materials.

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L a s e r c u t t i n g
http://en.wikipedia.org/wiki/Laserhttp://en.wikipedia.org/wiki/Laser


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N :0 0 3 / 1

2 1 0 1 T R

0 0 2

P r i n c i p l e o fl a s e r c u t t i n g

4

1

2 3

5 8 7 9 6

1 . A u x i l i a r y g a s

2 . C u t t i n g h e a d 3 . P r o f i l e f o l l o w e r 4 . F e e d r a t e 5 . C a s t M a t e r i a l 6 . S c a l e s ( f r o mc a s t i n g ) 7 . C u t t i n g f a c e 8 . Z A T 9 . C u t t i n g w i d t h

D o c .R o f i nS i n a r


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Advantages of laser cutting over mechanical cutting vary

according to the situation, but two important factors are the lackof physical contact (since there is no cutting edge which canbecome contaminated by the material or contaminate thematerial), and to some extent precision (since there is no wear onthe laser). There is also a reduced chance of warping thematerial that is being cut, as laser systems have a small heat-affected zone. Some materials are also very difficult orimpossible to cut by more traditional means. One of thedisadvantages of laser cutting includes the high energy required.

Comparison to mechanical cutting


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OPTICS
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Collimating Optics: Plano-convex lenses; copper totalrflectorReflective and transmissive collimating optics are

used in beam delivery systems to maintain beamcollimation between the laser resonator and the focusing

optics. Reflective collimators typically use Cu totalreflectors, while transmissive collimators typically use

ZnSe lenses.
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P h a s e R e t a r d e r s

Ragged Cut: produced by linearlypolarized light

Clean Cut: produced by circularlypolarized light

R e f l e c t i v e p h a s e r e t a r d e r i n t ot h e b e a m d e l i v e r y p a t he l i m i n a t e s k e r f v a r i a t i o n s b yc o n v e r t i n g l i n e a r p o l a r i z a t i o nt o c i r c u l a r p o l a r i z a t i o n .C i r c u l a r p o l a r i z a t i o n c o n s i s t so f e q u a l a m o u n t s
http://www.iiviinfrared.com.php5-1.dfw1-1.websitetestlink.com/sites/default/files/images/rpr_clean_cut.jpghttp://www.iiviinfrared.com.php5-1.dfw1-1.websitetestlink.com/sites/default/files/images/rpr_ragged_cut.jpghttp://www.iiviinfrared.com.php5-1.dfw1-1.websitetestlink.com/sites/default/files/images/rpr.jpg


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PARA BOL IC MIRROR

P a r a b o l i c m i r r o r s a r e d e s i g n e df o r r e f l e c t i n g a n d f o c u s i n g t h el a s e r b e a m t h r o u g h 9 0 d e g r e e s .
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N :0 0 8 / 1 2 1

0 1 T R

0 0 7

P e r f o r m a n c e s o f a C O2 l a se ro f 3 0 0 0 W

S T E E L 2 0 m m S TA I N L E S S S T E E L 1 0 m m B R A S S 3 m m A L U M I N I U M 8 m m C E R A M I C S 8 m m P. M . M . A . 5 0 m m P O LY C A R B O N AT E 2 5 m m W O O D 3 0 t o 5 0 m m


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A d v a n t a g e s o f t h e l a s e r c u t t i n g u s i n gC O 2

N o s t r e s s / l o a d o n t h e c o m p o n e n t

N o t o o l w e a r N o d e f o r m a t i o n o f t h e m a t e r i a l s H i g h f l e x i b i l i t y o f u s e P r e c i s i o n o f 0 , 1 m m Ve r y h i g h r e p e a t a b i l i t y S a v i n g o f m a t e r i a l L a r g e r a n g e o f m a t e r i a l s f o r c u t t i n g H i g h c u t t i n g s p e e d R e d u c e d c o s t o f u s e


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N : 011/121 01 TR 010

D r a w b a c k s o f C O 2 l a s e r c u t t i n g

H i g h c o s t o f e q u i p m e n t

L o w y i e l d D i f f i c u l t y o f u s e C o n s i d e r a b l e r e f l e c t i o n r a t e f o r c e r t a i n

m a t e r i a l s o f 1 0 , 6 m D i s e n g a g e me n t o f f u m e s a n d v a p o u r s

R i s k o f c a r b o n i s a t i o n f o r c e r t a i n ma t e r i a l s


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Welding

In laser welding we must distinguish between two main processes: thermal conductivity welding and deep

penetration welding . In thermal conductivity welding, the materials to be joined melt as a result of absorption of

the laser beam on the surface of the material, and the associated conduction of heat. The solidified smelt joins the

materials. The depth of the weld in this process is typically < 1 mm.Deep penetration welding, which begins at an energy density of approx. 10 6 W per cm 2 , is based on the creation of

a vapor capillary in the material. To achieve this, it is necessary to heat the material locally to its evaporation point.

The resulting vapor pressure in the material creates a capillary approx. 1.5 times the diameter of the focal spot of

the laser beam, which is moved through the material by the movement system, following the contour to be welded.

The hydrostatic pressure, the surface tension of the smelt, and the vapor pressure in the capillary compensate

each other, so that the capillary (often referred to as the "keyhole") does not collapse. The total reflection within

the keyhole guides the applied laser beam deep into the material, in such a way that today, given sufficient laser

power, weld depths of up to 25 mm (steel) can be achieved.

Steels and aluminum are the classic area for laser welding. But in principle, all materials that can be welded using

traditional methods can also be welded with lasers, often at higher speed and quality compared with the traditional

processes.


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LASER CUTTING AND WELDING MACHINE

Sequence of operation


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The Loading SystemThe loader takes a sheet from the stack and loads it on the loadingtable in front of the clamping bench. The sheet is taken by meansof suction cups connected to a vacuum system. A hydrauliccylinder drives the vertical movements; an electrical motor drivesthe horizontal movement.

1.The Loadin g Sys tem


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The unloader takes parts from the cutting area and drops them on theunloading conveyor. The sheet is taken by means of suction cups

connected to a vacuum system. A pneumatic cylinder drives the verticalmovements of the entire unloading platform.

1.a .The Unlo ading System


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Whenever a sheet feed-in cycle iscommanded, a sheet will be transported fromthe loading table in front of the clamping bench

to the appropriate position where cutting can

2.Feeding Firs tSh eet in to the Clam pin gBench

3 TheCutt in gand Welding


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As soon as the first sheet has been fed in, and the transport rolls have been movedDOWN, the cutting cycle starts:

The U -axis moves to its end position with the unloader platform above the unloadingconveyor. This allows the Y-axis to be set at "full stroke". The Y -axis moves to the edge of the first sheet on the exhaust table, and the edgesof the sheet are cut away, as are the window holes. When cutting on the exhaust table is finished, the Y -axis moves to its position abovethe clamping bench. Unloading of the window cutouts can start (also refer to "TheWindow Cut-out Unloading Cycle"). The unloading cycle runs in channel 2, allowingchannel 1 to continue trim-off and welding. The cutting head cuts (trims) away the edges in the clamping bench of the firstsheet. Then a second sheet is fed in the clamping bench, after which its edges in theclamping bench are also cut (trimmed) away. A head change is performed, rotating the cutting head away, and replacing it by thewelding head. The clamping bench closes (moves OUT), and the two sheets are welded to eachother: first some points are welded, afterwards the entire weld seam.

3.The Cut t in g and WeldingCycle


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3.e. Laser Head.


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4.f.Welding Position


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3.g.Cutting Position


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As long as the Y-axis is positioned at the clampingbench, the U-axis can move freely over the exhausttable to remove the scrap parts (windows) from thecutting area (U-axis is set at full stroke)

4.The Wind ow Cut-ou t Unloading Cycle


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5 .Trans po rt ing the Sheets fo r the Next

Cut t ing and Welding CycleWhen the welding actions have been performed, and all window cutouts have beenremoved, the joint sheets are to be transported further in the direction of the unloadingarea, preparing for another cutting and welding cycle: The transport rolls in the exhaust are moved UP.

The U -axis is moved to a position above the exhaust table where it is able and allowedto grab a sheet. The rear gripper opens and moves OUT. The front gripper opens and moves towards the sheet. The front and rear gripper close and clamp the sheet. The clamps at the loading side and the cutting side of the clamping bench move UP(stop clamping).

The bench rolls are activated in forward direction, the unloading rolls are activated inforward direction, and the U-axis pulls the clamped sheet over a defined distancetowards the unloading area.


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The bench rolls and unloading rolls are stopped.

The transport rolls in the exhaust are moved DOWN. The clamps at the cutting side of the clamping bench move DOWN(start clamping). The front and rear gripper open. The U -axis moves to its end position with the unloader platformabove the unloading conveyor.

At this moment the cutting on the exhaust table can start, a thirdplate can be loaded into the loading side of the clamping bench, andcutting and welding the third plate to the second one can becommanded.


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When the final sheet has been welded to the previous one, the joint sheets are tobe transported further in the direction of the unloading area, preparing for thefinal cutting:

The transport rolls in the exhaust are moved UP.

The U -axis is moved to a position above the exhaust table where it is able andallowed to grab a sheet. The rear gripper opens and moves OUT.

The front gripper opens and moves towards the sheet.

The front and rear gripper close and clamp the sheet.

6.The Last Cu t t ing Cycleand Un loading th eFinis h ed Par t


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The clamps at the loading side and the cutting side of the clamping bench moveUP (stop clamping). The bench rolls are activated in forward direction, the unloading rolls are activatedin forward direction, and the U-axis pulls the clamped sheet over a defined distancetowards the unloading area. This time the final sheet is completely pulled out of theclamping bench. The bench rolls and unloading rolls are stopped.

The transport rolls in the exhaust are moved DOWN. Note that the gripper clampsdo not release the sheet this time. At this moment the final cutting on the exhaust table can start. After the cutting, the gripper clamps are opened, and the sheet is released. Thecutouts are removed as described in chapter 4.10.4 "The Window Cut-out UnloadingCycle".

Finally, after the cutout removal, the gripper transports the joint sheets (and theremaining scrap part of the last sheet) onto the unloading rolls. These rolls can thentransport the finished part to the point where the part will be removed from themachine by means of external equipment.


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There are a total of 5 scrap conveyors used on this machine.

The Bench Conveyor: The scrap parts resulting from cutting in theclamping bench fall on this conveyor belt. The conveyor belt then pullsthe scrap out of the machine.The Cutting Conveyors: The small scrap parts (resulting from cutting onthe exhaust table) are collected by a part collector (exhaust funnel) andfall onto one of two conveyor belts. These conveyor belts transport the

scrap onto a third conveyor belt. This last conveyor belt then pulls thescrap out of the machine.The Unloading Conveyor: The window cutouts (larger parts) that areunloaded via the unloader platform fall on this conveyor belt. Theconveyor belt then pulls the cutouts out of the machine.

7.The Scrap Co nv eyors


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A gas circuit protects the optical path from dust. The gas supply forthis circuit is derived from the air dryer. During an X-, Y- or Z-axistravel, a gas stream is blown under the bellows. This stream createsan over-pressure in the optical path and this prevents dust from fallingdown.

Purg e Circu i t for the Opt ical Path


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Al ignm ent Procedure for th e Opt ical Path

The beam travel must be coaxial with the travelling-axes of the mirrorsalong the machine axes X, Q, Y and Z. The laser-support and eachmirror on the machine should be aligned in order to obtain this situation.

A complete alignment (machine and laser) has been done wheninstalling the machine and should only be done in some particular cases

(e.g. after a service intervention on the laser cavity).


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TH NK YOU

laser basics welding

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