Scanner welding – Highly productive processing with no downtime

Scanner welding enables highly productive and flexible production line layouts, making welding in series production faster, more accurate, and thus more cost-effective than traditional welding processes.

In scanner welding, beam guidance is performed with mobile mirrors. The beam is guided by changing the angles of the mirrors. A processing field determines which weld can be carried out with the highest dynamics and precision. The processing speed and size of the focus diameter at the workpiece depends on the imaging properties of the optic, the beam incidence angle, the laser beam quality and the material.

Using the method of an additional lens system, the focus point can also be offset in the Z direction, in order to process three-dimensional components completely, without moving either the processing head or the part.

Due to the very fast translation movements, downtime is nearly eliminated, and the laser unit can produce at close to 100% of the available fabrication time.

During welding, the scanner optics can also be guided over a workpiece in conjunction with a robot. This “flying” movement is what inspired the term “welding on the fly”: The synchronization of the robot and scanner optic in real time. The use of a robot increases the workspace significantly, permitting true three-dimensional part processing.

A convenient editor can be used to program a PFO. It can construct and save welding figures on a workpiece.

High-power disk lasers with high beam quality are used as beam sources. One or more flexible fiber-optic laser cables lead the laser light from the laser unit to the processing station.

Spot and seam welding with lasers

With laser welding, you can create single joining spots or weld in continuous wave mode.

The weld geometry describes how the parts fit together. For example, they may overlap or butt up against each other. The mechanical properties are the first thing to consider when defining the weld geometry.

Is a continuous weld required, or will the weld consist of individual welding spots? Is the weld made up of a large number of short lines or lots of small circles? Here, too, the decision of which type of weld to use depends on two important factors: the required strength of the weld and the maximum amount of heat input into the component.

Different kinds of joints require different operation modes of the laser device.

Continuous wave mode
In this mode the laser medium is pumped continuously and emits a continuous laser beam./p>

Pulsing
In pulsed mode, the gain medium is pumped in bursts to generate short laser pulses. Power, duration and frequency of the laser pulses are important parameters for material processing.

Building shapes out of powder and wire

Deposition welding is a generating process for surface finishing as well as the repair and modification of existing components. Depending on the task at hand, either manual or automated laser deposition welding is used.

Manual laser deposition welding

In the case of manual deposition welding, the welder guides the filler material “by hand” to the area to be welded. A thin wire with a diameter between 0.006 and 0.02 inches is primarily used as filler material in this process. The laser beam melts the wire. The molten material forms a strong bond with the substrate, which is also melted, and then solidifies leaving behind a small raised area. The welder continues in this fashion, spot by spot, line by line, and layer by layer, until the desired shape is achieved. Argon shields the work process from the ambient air. Finally, the part is restored to its original shape by grinding, milling, turning, EDM etc.

When coating the surface, several powder coatings are either melted onto one another or next to one another, as required. The individual welding paths must precisely overlap in order to achieve a texture that is free from errors.

Automated laser deposition welding

In automated deposition welding, the machine guides the filler material to the area to be welded. Although the material can also be a wire, this process primarily uses metal powders. Metal powder is applied in layers to a base material without pores or cracks. The metal powder forms a high-tensile weld joint with the surface. After cooling, a metal layer develops that can be machined. A strength of this process is its ability to build up a number of metal layers.

Heat conduction welding

In heat conduction welding, the laser beam melts the mating parts along a common joint. The molten materials flow together and solidify to form the weld.

Heat conduction welding is used to join thin-wall parts. One example is corner welds on the visible surfaces of device housings. Other applications can be found in electronics. The laser produces a smooth, rounded seam that does not require any extra grinding or finishing. Pulsed or continuous wave solid-state lasers are used in such applications. In heat conduction welding, energy is coupled into the workpiece solely through heat conduction. For this reason, the weld depth ranges from only a few tenths of a millimeter to 1 millimeter. The heat conductivity of the material limits the maximum weld depth. The width of the weld is always greater than its depth. If the heat is not able to dissipate quickly enough, the processing temperature rises above the vaporization temperature. Metal vapor forms, the welding depth increases sharply, and the process turns into deep penetration welding.

Deep penetration welding

Deep penetration welding requires extremely high power densities of about 1 megawatt per square centimeter. In this process, the laser beam not only melts the metal, but also produces vapor.

The dissipating vapor exerts pressure on the molten metal and partially displaces it. The material, meanwhile, continues to melt. The result is a deep, narrow, vapor-filled hole, or keyhole, which is surrounded by molten metal. As the laser beam advances along the weld joint, the keyhole moves with it through the workpiece. The molten metal flows around the keyhole and solidifies in its trail. This produces a deep, narrow weld with a uniform internal structure. The weld depth may be up to ten times greater than the weld width, reaching 1 inch. The laser beam is reflected multiple times on the walls of the keyhole. The molten material absorbs the laser beam almost completely, and the efficiency of the welding process rises. If CO₂ lasers are used for welding, the vapor in the keyhole also absorbs laser light and is partially ionized. This results in the formation of plasma, which puts energy into the workpiece as well. As a result, deep penetration welding is distinguished by great efficiency and fast welding speeds. Thanks to the high speed, the heat-affected zone is small and distortion is minimal. This process is used in applications requiring deeper welds or where several layers of material have to be welded simultaneously.

Hybrid welding

By combining laser welding and one other welding process, special applications for steel construction can be achieved.

Hybrid techniques refer to processes in which laser welding is combined with other welding methods. Compatible processes are MIG (metal inert gas) or MAG (metal active gas) welding as well as TIG (tungsten inert gas) or plasma welding.

An example that illustrates the advantages is in the ship building industry. Large steel plates as long as 65 feet and 0.6 inches thick are welded together. The gaps between the plates, however, are too large for the laser beam to bridge by itself. To get around this problem, laser welding is combined with MIG welding. The laser delivers the high power densities needed for the deep welds and enables high welding speeds. This, in turn, reduces heat input and distortion. Meanwhile, the MIG torch bridges the gap between the parts and closes the joint using filler wire. On the whole, the hybrid technique is faster than MIG welding alone, and the parts are subject to less distortion.

Soldering

In soldering, the mating parts are joined by a filler material, or solder. The melting temperature of the solder is lower than that of the component materials. As a result, only the solder is melted.

The mating parts are merely warmed. Once melted, the solder flows into the gap between the parts and bonds with the surface of the workpiece (diffusion bond). Soldering a joint requires access to only one side of the joint. The thin gap between the components functions like a capillary, drawing the liquid solder into the joint.

The soldered joint is only as strong as the solder material. In a related process called brazing, solders made of copper and zinc can produce joints that are as strong as those achieved during welding. The surface of the solder seam is smooth and clean, forming a nicely curved transition to the workpiece. Since solder seams do not require finishing, they are often used in the automotive industry for making body parts such as trunk lids or car roofs. No processes area required prior to painting except a simple cleaning.

Other applications can be found in mixed constructions. Components made of dissimilar materials often cannot be welded or, if they can, only with limited success due to the very different melting points of the materials. Joining aluminum and steel is one such example. For these and similar joining tasks, soldering is the perfect alternative.

The information shared here is from Trumpf Laser to see more about laser technology and applications visit their website here: http://www.us.trumpf.com/products/laser-technology/solutions/applications.html