The laser welding machine is highly automated, and the welding process is simple. Non-contact operation methods can meet the requirements of cleanliness and environmental protection. Treating a workpiece can increase productivity. The finished workpiece has a beautiful appearance, small weld, large welding depth, and high welding quality. Laser welding machine is widely used in dental denture processing, keyboard welding, silicon steel sheet welding, sensor welding, battery sealing cover welding, and the like. However, the cost of laser welding machine is relatively high, and the accuracy requirements of the workpiece assembly are relatively high, and these aspects still have limitations.
How does the Laser Welder work?
Laser welding uses high-energy laser pulses in partially heating of materials. The energy of the laser radiation is diffused into the material by heat transfer, and the material is melted to form a particular molten pool. It is a new type of welding method mainly used for welding of thin-walled materials and precision parts. It can achieve spot welding, docking welding, pin welding, sealing welding, etc., has high aspect ratio, small welding width, and small thermal impact regions. Small variation, fast welding speed, smooth and beautiful, welded, smooth, welding, high weld, high weld, no porpity, precise control, small focus, high positioning accuracy, easy to achieve automation.
Working principle of laser welding machine: laser welding can be achieved by continuous or pulsed laser beams. The laser welding principle can be divided into thermally conductive welding and laser deep penetration welding. The power density for thermal welding is less than 104 ~ 105W / cm2. At this time, the penetration depth is shallow and the welding speed is slow; when the power density is greater than 105 ~ 107W / cm 2, the metal surface is depressed in the heat of the “aperture” to form deep pendulum welding. Fast welding speed and large aspect ratio.
The heat conduction laser welding principle is: laser radiation heating surface treatment, and surface heat diffuses into the interior through heat conduction. The workpiece is melted by controlling laser pulse width, energy, peak power, and repetitive frequency and other laser parameters, the workpiece is melted to form a particular molten pool.
Laser welding machines for gear welding and metallurgical steel sheets mainly involve laser deep penetration welding.
Laser deep penetration welding typically uses a continuous laser beam to complete the connection of materials. The metallurgical physical process is very similar to the electron beam welding, that is, the energy conversion mechanism is completed by the “key hole” structure.
Under a sufficiently high power density laser irradiation, the material will evaporate and form a small hole. This steam filled hole is like a black body, absorbs almost all incident beam energy. The balance temperature in the cavity reached approximately 2500 0 ° C. The heat is transferred from the outer wall of the high temperature chamber to the metal around the molten chamber.
The small hole is filled with high temperature steam produced by continuous evaporation under the beam irradiation. The four walls of the small holes are surrounded by molten metal, and the liquid metal surrounds the solid material (in the most conventional welding process and laser conductive welding, the energy deposited on the surface of the workpiece is first delivered to pass transfer).
The liquid flow of the wall and the surface tension of the wall layer remain in the dynamic balance of steam pressure. The beam continuously into the small hole, and the material outside the pores is continuously flowing. When the beam moves, the small hole is always in a stable flow state.
That is, the small holes around the hole wall and the forward speed of the molten metal are moved forward. The molten metal fills the gap of the small hole and condensation, and forms a weld.
And the above process occurs very fast, so the welding speed can easily reach a few meters per minute.
How to use the laser welder?
Hand-held laser welding machine, using infrared positioning, flexible and convenient, welding, no consumables, smooth welding, smooth, not easy to deform, mainly for laser welding long distance and large workpiece, widely used in large and large workpieces, widely used medium sheet metal Gold, cabinet and chassis, long distance spots, flush, continuous welding, inner corners, outer corners and large workpieces, such as aluminum alloy gates and window frames, stairs, elevators, and stainless steel furniture.
Laser welding can be applied to titanium, nickel, tin, zinc, copper, aluminum, chromium, niobium, gold, silver and other metals and alloys of welding, steel, Kovar, and other alloys of the same material. It can be applied to welding of various heterogeneous metals, such as copper-nickel, nickel-titanium, copper-titanium, titanium-molybdenum, brass-copper and low carbon steel copper. At the same time, it is also widely used in mobile phone communications, electronic components, glasses and watches, jewelery, hardware, precision equipment, medical equipment, car parts and craft gifts.
How to choose a suitable laser welder?
Need to consider the following key elements:
1. Optical characteristics: spot size (laser rod diameter, fiber diameter and type, output head parameter), focal plane height, depth of field, field position, emission angle;
2. Control characteristics: Feedback control mode, selection of power waveforms. The optical characteristics of the laser welding machine can be determined at the time of the sample, and when the product is first trial, the user can intuitively determine the welding effect, so I will not repeat it here, but focus on laser control characteristics affect laser welding consistency.
The laser welding machine currently sold in the market is mainly divided into two types of control characteristics: current negative feedback and laser power negative feedback.
The current negative feedback is a control method of controlling the current of the laser pump xenon lamp, and keeps the xenon current constant each time. However, the current of the laser output power is not linearly proportional to the current of the pumped xenon lamp, and as the pump’s xenon lamp is longer, the electro-optical conversion efficiency is significantly reduced, which will reduce the output laser energy, thereby affecting the output laser energy welding. Consistency of the effect. gender.
Laser power negative feedback is a control method in which the photodetector is added to the output of the laser chamber, and the detected laser power is compared to the required laser power to control the pump current of the xenon lamp.
Laser power negative feedback is divided into real-time negative feedback and non-real-time negative feedback. Real-time negative feedback is a control method that compares the detected laser power to the laser power required in the laser power pulse, and then controls the pump current of the xenon lamp. Non-real-time negative feedback is compared to the set waveform of the previous pulse, and then determine the current size of the next pulsed laser pump xenon lamp.
Further, a negative feedback control of the laser power can easily control the waveform of the laser power. In fact, for different materials, the use of different laser power waveforms can make the welding effect more refined, and sometimes even cannot be welded. By changing the laser power waveform, the material can also achieve a better welding effect.
When the laser power waveform is selected, in general, the same laser energy, a wider pulse width, and the larger solder joint; the higher the peak of the laser power waveform, the deeper the welding point. Currently, there is no complete laser power waveform setting method. Users can gradually explore laser power waveforms suitable for their products during use.
The choice of laser welding machine is very important for the production of batch processing; therefore, if the condition is permitted, the user can attempt to use laser power real-time negative feedback welding machine to improve product quality.
