Some Useful Guides To Buy the Laser Welding Machine Laser welding is a welding technique by radiating laser beam to the surface of processing workpieces and focalizing laser beam through optical system in order to form a highly concentrated heat-affected zone in very short time, where the cooling crystallization of welding zone becomes solid welding spot and weld joint. According to different types and working modes of laser, the common laser welding methods can be divided into two types one is pulse laser welding which is mainly used in thin metal; another one is continuous laser welding which is used for big and thick workpieces.
Source : intechopen The welding effects are mainly influenced by the choices of welding material, laser welding machine and processing workbench. While whether melding would occur and the melding degree are determined by the time laser works on the material surface and power density as well as peak power. As long as the above parameters are well controlled, various laser welding can be carried on. Beam focal position is one of the most important parameters in laser welding process, only when the focus is within the optimum location scope, the best penetration and weld shape can be achieved.
Major characteristics of laser welding The major traits of laser welding are as following: 1. Laser welding is non-contact welding, so it needs no pressing in the process. It is high in weld speed, efficacy, depth and it has little deformation. Laser welding can take place either in room temperature or special condition (such as closed space), which need simple welding equipment and generates no X-ray. 2. It is able to weld refractory metal materials, even non-metallic material like china and organic glass. Special-shaped material also can be welded since laser welding is quite flexible and is able to apply remote welding. 3. Slight flare can be generated by focused laser beams which can positioning precisely and be applied in mass automatic production of micro and small workpieces' installation and welding. 4. Beam split is easy to be realized by time and space and multiple beam can be processed all at once, providing conditions for more precise welding. 5. It has no problems like tool wear and tool change since laser welding is non-contact processing. It doesn't need to use electrode, so there is no worry about electrode pollution or damage. Laser welding is easy to auto-welding in high speed. It can be digitally controlled or controlled by computer. However, there are some limits of laser welding First, the cost and initial equipment investment on laser and the relevant systems are high. Secondly, it requires high assembly accuracy for weld in processing period and it should have no obvious deviation of beam on workpieces. Moreover, the weld thickness is less than that of electron beam welding and it is difficult to weld metal of high reflectivity.
Source : cloudfront Techniques of laser welding 1. Welding between slices. It usually adopts manual and automatic welding, including butt welding, end welding, central through melt welding and center hole melt welding. 2. Welding between wires. It typically adopts manual and semi-automatic welding, including wire & wire butt welding, cross welding, parallel overlap welding and T-type welding. 3. Welding between wire and block element. Laser welding makes it possible to connect wire and block element and the block can be any shapes. The dimensions of wire should be noted. 4. Welding between different metals. It is possible for some particular combination of materials for welding between different metals. It should pay attention to the weldability and welding parameter range. 5. Repairing welding between block elements. It usually applied in repairing mould.
Parameters that Influence the Quality of Laser Welding Machine 1. Laser pulse energy Laser pulse energy is the maximum output energy from a single laser pulse. It is a major parameter of laser which determines the maximum energy of laser. When applied in mould repairing, laser energy below 70J can meet demands in any occasion. Too much energy is just a waste and has no use at all, which brings increasing volume of power supply and reduces the efficiency. 2. Laser beam flare diameter Laser beam flare diameter is a key parameter to reflect performance of laser design, which determines the power density and processing scope of laser. If the optical design is professional, 0.2mm-2mm is the best scope for laser beam flare diameter. It is a strict test for laser whether the laser beam flare diameter can be controlled as 0.2mm. 3. Laser pulse frequency Laser pulse frequency reflects the amount of pulse energy produced by laser in a second. When applied in mould repairing, 15Hz is enough for welding. Too high frequency will make too low pulse energy, thus making welding failed. 4. Laser pulse waveform and relative light absorption rate of materials to be welded. Laser pulse waveform is also an important problem in laser welding process. When high strength of laser beam reaches the material surface, 60 %~98% of the laser energy will be lost by reflection and the reflectivity is changeable by the temperature of the material of surface. As a result, it should input laser of different waveforms according to different metal, so as to make the composition of crystallization in weld joint is the same to the base metal, achieving high-quality weld joint. 5. Temperance characteristics feedback control method and choice of power waveform When it comes to the choice of laser power waveform, in the condition of same
laser energy, the wider the pulse width, the larger the welding spot; the higher the peak power the deeper the welding spot.
Quality Control of Laser Welding With the development of laser, laser welding technology is continuing to mature. However, various questions and problems may occur in the practical welding process. It is a very crucial part to know how to distinguish the causes and how to solve the quality problems. First, it is necessary to check the quality of welding quality. There are visual inspection and destructive inspection. Visual inspection is a way to judge whether the welding products are qualified by working experience, which is insufficient to reach a decision. So destructive inspection is needed, in which welding base metal will be torn to confirm the quality. Moreover, tensile strength test is a plus. Secondly, analyze the causes according to the phenomenon. Generally speaking, if welding fabrication defects appear, it is probably the problem of material which should be checked and changed; if defects appear in the same part of the products, it is probably the problem of workbench and fixture; if weld penetration and dry joint occur occasionally, it is necessary to check energy stability of welding machine or workbench or fixture. Thirdly, strengthen welding quality assurance management. In welding process, first, press instrument is necessary to check and ensure stable pressure; secondly, monitoring on electricity is a must to avoid undulation of supply voltage; thirdly, pay attention to the thickness of the workpieces and cladding material as well as the metal composition to avoid defective weld products. Matters Needing Attention for Laser Welding Just like ordinary lights, laser also has bioeffects which can benefit human as well
as damage human eyes, skin and nervous system without protection. In order to ensure safety and protection in welding process, it must be under strict control on laser hazard and special attention should be paid to engineering control, personal protection and security management. 1. Engineering control Engineering control means the safety precautions on the structure of laser or Laser process system, which includes shield, safety interlock, safety light path, key-operated switch and beam termination. 2. Personal protection It mainly means wearing laser protective clothing, eyeglasses, mask and gloves. 3. Security management Security management contains setting up specialized agency or personnel and clarifying the responsibility as well as rights, including safety training and medical monitoring, etc.