Today's requirements for vehicles with an internal combustion engine are characterized by more sophisticated emission regulations, rising fuel prices and higher driver's demand for driving dynamics, and comfort in line with increased environmental awareness. That's why more and more auto manufacturers around the world are concentrating on electric vehicles. There are various components that make up an electric vehicle, batteries and electric motors are the core of these electric vehicles and are built using a combination of different materials, including highly reflectively aluminium-based alloys and copper. Electrical batteries and motors require welding techniques that can join light and electrically conductive metals such as aluminium and copper alloys without any welding defects. The quality of the weld is very important because it must operate safely and reliably throughout the life expectancy of the vehicle manufacturer, which is at least ten years.

At Everfoton, we developed a range of low- and high-power single-mode (SM) fiber lasers, including new lasers called Variable Beam Profile (VBP) lasers for welding electrical mobility materials. The VBP laser uses a dual beam outlet to produce a central point, surrounded by another concentric ring of laser light. The power in the central and annular points can be controlled independently, allowing for very careful control of the dynamics of the modulated fusion basin.  VBP fiber lasers are available for up to 12 kWs of total power, with different centre-ring ratios and different power levels that can be adapted to specific applications. The result is that the welding process is more stable and maintains consistently during welding, regardless of surface variations in the workpiece, thus overcoming the limitations experienced with traditional fiber lasers.

Laser cutting is primarily a thermal process in which a focused laser beam is used to melt material in a localized area. A co-axial gas jet is used to eject the molten material and create a kerf. Continuous cutting is achieved by moving the laser beam or workpiece under CNC control. The Improvements in accuracy, edge squareness and heat input control mean that the laser process is increasingly replacing other profiling cutting techniques, such as plasma and oxyfuel. Some of these laser cutting advantages include:

• Narrow kerf widths of straight edges and generally good appearance;
• Minimum heat affected zones adjacent to the cut edge;
• Minimum heat resulting in minimal distortion of the workpiece;
• Fine control of average power eliminates excess burning during acceleration and deceleration;
• No mechanical distortion of the workpiece;
• No cutting tool wear, maintenance or replacement.

Everfoton has developed several high-power fiber lasers (1.0-30kW) in both single and multi-mode for cutting ferrous and non-ferrous metals.  Laser and processing parameters have been developed to cut different materials and thicknesses with different assist gases i.e., oxygen, air, nitrogen and argon. The cutting quality in terms of cut speed, cut edge appearance, burr formation and kerf width has been analyzed. The photographs show laser cutting edges of various materials and assist gases, including thin aluminum sheet cut at high speed (>53 m /min).  

The high-power heat source produced by a laser beam is ideally suited for surface modification. Laser heating produces local changes of the surface of the material while leaving intact the properties of most of the particular components. The main laser surface engineering applications can be broken down into three main areas (Figure 1). The following processes may also be divided into those depending on metallurgical changes in the surface of the bulk material i.e., transformation hardening, annealing, grain refining, glazing and shock hardening, and those involving a chemical modification to the surface by addition of new material i.e., alloying and cladding.

• Heating without melting is commonly known as heat treatment. This involves solid-state transformation, so that surface of the metal is not melted. The portion of the beam power absorbed by the material is controlled by the absorption of the surface of the material. Both mechanical (hardness, abrasion, resistance etc.) and chemical properties, (corrosion resistance etc.) can frequently be greatly improved by the metallurgical reactions produced during these heating and cooling cycles (Figure 2) ;
• Heating with melting, i.e., laser glazing, surface homogenization, remelting. This method produces very fast heating, melting and cooling for changing surface properties;
• Melting with addition of material, i.e., cladding, alloying impregnation, involves melting of the surface plus material added to the surface to form a modified surface layer (Figure 3).

The increasing complexity of microelectronics/ engineering devices and the requirement for higher yields and automated production systems place stringent demands on the assembly techniques and performance requirements of materials and joining techniques.  This increased interest in the use of lasers for microwelding applications across a range of applications.  The term micro-welding also known as precision welding, refers to welding the parts that have a weld bead size <1mm and a weld penetration depth <1mm. Besides the size of the weld seam and the depth of penetration of the weld, other laser microjoining requirements are:

• Very fine welds (spot sizes can vary approximately. 10um up to 100um);
• Decreased distortion and heat affected area;
• Reliability and stability of the process (pulse-to-pulse stability for spot welding);
• High processing speed (welding using a scanner);
• Welding of reflective materials;
• Welding of dissimilar materials.

Laser microwelding is used for joining high value miniature components in a range of industries i.e., Electronics, Telecommunications, Automotive & Medical Industry (Table 1). Compared to conventional microwelding methods i.e., resistance, flash, arc, TIG, and MIG, plasma laser micro-welding offers several advantages i.e.  

• Low heat input: The weld energy is delivered only to the point where it is needed and with exceptional control;
• Clean welds: In addition to the aesthetic advantages, clean welds provide products that are easier to sterilize or integrate into other joints;
• Strong welds: The laser offers high strength and a minimum number of welds;
• Hermetic welds: In contrast to soldering or brazing, lasers can provide flawless hermetic welds essential for many micro applications.

 Table 1: Examples of microwelding applications

Everfoton offers several low-power SM CW and Quasi-CW optical fiber lasers for micro-welding applications and some examples of micro-welding are highlighted in (Figure 1). 

Laser cleaning uses a focused beam of light to eliminate contaminants. The term "ablation" refers to the processes of removing material from surfaces and is accompanied by a shockwave that moves outward, affecting the surrounding surfaces. Laser energy is absorbed into the surface material, leading to the generation of a plasma plume of ablation products. The actual absorption of the laser beam depends on the reflectivity of the material, the quality of the surface and the properties of the contaminant on the surface. When materials are processed with a laser beam, the surface characteristics of the materials may change. In some applications, a surface should be kept finely polished, while in others, the surface should be coarse. Therefore, for a successful finish, laser cleaning techniques should consider the properties of both the material being cleaned and the quality of the surface, and the properties of the contaminant on the surface to be removed. Some of the laser cleaning applications comprise.

• Surface treatment

Laser cleaning can replace chemical treatments of metal surfaces that have been prepared for joining process i.e., soldering, brazing, welding, and gluing. Substances like petroleum, dirt, fat, and hydrates can be removed in one step using fiber lasers. Low energy short pulses (<1 mJ/pulse) from the high frequency laser leave a metallic surface at its initial roughness.

• Restoration and renovation

One of the most popular laser cleaning applications is the elimination of rust. Rust has a high absorptivity; consequently, a thin layer can be removed as easily as lubricant, making the laser a powerful tool. Similar applications, such as the removal of dirt or anodized finishes and the refurbishment of stainless-steel parts, are widely adopted by the automotive industry. For these applications, QCW fiber laser cleaners are available in fixed and handheld cleaning machines.

• Metallic & no-metallic coatings

Some industrial operations that use metal parts require the removal of a layer of metal covering the base metal—for example, the removal of zinc from galvanized steel. The thickness of a zinc layer can range from a few microns (galvanoplasty) to a few millimeters (metallization). In such operations, it is often necessary to completely remove the coating on the surface of the base metal. High output CW fiber lasers can be used to remove non-metallic coatings. In this case, a paint/coating is burned or evaporated with the high temperature metal plasma plume, and the shock waves expel the ash and fumes. Such an installation has been proven to remove even dense coatings, silicon lubricants, or heavy rust.

3D printing or additive manufacturing is a method of manufacturing parts directly from a digital model using a layered material construction approach. These materials take the form of powders, and the laser works one layer at a time through the powder to form an object. Metal, plastic, and glass are some of the most important materials used to create a powder. The selected material passes through a super powerful crusher until it is a form of powder. This tool-free manufacturing method can produce fully dense metal parts in a short time, with great accuracy as shown in Figure 1. 

Using 3D modeling to create prototypes has become standard across manufacturing industries i.e., for aviation, oil and gas, marine and automotive applications. This method is also very useful for making small, complex, low-volume metal parts such as medical, jewellery and dental parts.

The main benefits of 3D printing are:

• Ability to design geometrically complicated pieces.
• Lower manufacturing costs.
• Ability to fabricate parts without tools.
• Get products on the market quicker.
• Replacement of inefficient manufacturing workflow.

A portable laser cleaning system with a fiber laser source can provide high or moderate peak power for various cleaning applications.  The fiber laser beam can remove surface layers and contamination from the surface without damaging the base material, and this cleaning process is appropriate for both metals and hard materials. The laser and processing parameters, i.e., average/peak power, frequency, and speed, can be optimized to enable the laser equipment to achieve good results in different types of applications such as paint stripping, removal of iron rust, sheet metal welding, metal surface processing and coating peeling. It may be used to clean some products including electronics, communication equipment, integrated circuits, powerlines, computer components, and electrical appliances.

The laser source and controller are housed in robust waterproof housing for maximum protection against harsh environments and rough use. A fiber cable routes the laser beam to the cleaning head equipped with a focusing lens. The complete equipment is air-cooled, free-standing, portable and mobile (the laser linear distance is 50-200m). This system has several advantages over conventional cleaning, that is:

• No chemicals involved – eco-friendly.
• The laser can operate for an extended period without maintenance.
• Capable of working in a dirty and challenging environment.
• Clean and easy process.
• Fast processing speed.
• Excellent result.
• Cost-effective.