First, the basic knowledge of ultrasonic metal welding ultrasonic metal welding is the use of high-frequency vibration waves transmitted to the two metal surfaces to be welded, under the pressure, the two metal surfaces rub each other to form a fusion between the molecular layers, The advantages are fast, energy saving, high fusion strength, good electrical conductivity, no spark, close to cold processing; the disadvantage is that the welded metal parts can not be too thick (generally less than or equal to 5mm), the solder joints can not be too large, and need to be pressurized.
2, welding advantages:
1) The welding material does not melt and is not fragile.
2), good electrical conductivity after welding, the resistance coefficient is extremely low or nearly zero.
3), the welding metal surface requirements are low, oxidation or plating can be welded.
4), welding time is short, no need for any flux, gas, solder.
5), welding without sparks, environmental protection and safety.
3. Suitable products for ultrasonic metal welding:
1) Nickel-metal hydride battery Nickel-metal hydride battery nickel mesh and nickel sheet inter-melting and nickel sheet inter-melting. .
2) Lithium battery, polymer battery copper foil and nickel sheet are mutually melted, and aluminum foil and aluminum sheet are mutually melted. .
3), the wires are mutually melted, and they are entangled into one and a plurality of mutually melted.
4), the wire and the name of the electronic components, contacts, connectors and mutual fusion.
5), the mutual melting of large-scale heat sinks, heat exchange fins, and honeycomb hearts of famous household appliances and automotive products.
6), electromagnetic switch, no fuse switch and other large current contacts, mutual melting of dissimilar metal pieces.
7) The sealing and cutting of the metal pipe can be water and airtight.
4, amplitude parameters
The amplitude is a key parameter for the material to be welded, which is equivalent to the temperature of ferrochrome. If the temperature is not reached, the welding will not be possible. If the temperature is too high, the raw material will be burnt or the structure will be destroyed and the strength will be deteriorated. Because the transducers selected by each company are different, the amplitude of the transducer output is different. After adapting the horn and the horn of different ratios, the working amplitude of the horn can be corrected to meet the requirements. The output amplitude of the energy device is 10-20μm, and the working amplitude is generally about 30μm. The transformation ratio of the horn and the welding head is related to the shape of the horn and the welding head, the front-to-back area ratio and other factors, and the shape is exponential. Variable amplitude, functional amplitude, stepped amplitude, etc. have a great influence on the ratio, and the area ratio before and after is proportional to the total ratio. Your company chooses welding machines of different company brands. The simplest method is to make the scale of the working welding head to ensure the stability of the amplitude parameters.
5, frequency parameters
Any company's ultrasonic welding machine has a center frequency, such as 20KHz, 40 KHz, etc. The working frequency of the welding machine is mainly the mechanical resonance frequency of the transducer, the horn, the horn and the horn. It is determined that the frequency of the generator is adjusted according to the mechanical resonance frequency to achieve uniformity, so that the horn operates in a resonant state, and each part is designed as a half-wavelength resonator. Both the generator and the mechanical resonant frequency have a resonant operating range. For example, the general setting is ±0.5 KHz. In this range, the welding machine can basically work normally. When we make each welding head, the resonant frequency is adjusted. The resonance frequency and design frequency error is less than 0.1 KHZ. For example, the 20KHz welding head, the frequency of our welding head will be controlled at 19.90-20.10 KHz with an error of 5‰.
6, the node
The welding head and the horn are designed as a half-wavelength resonator with an operating frequency. Under the working condition, the amplitude of the two end faces is the largest and the stress is the smallest, and the amplitude of the node corresponding to the intermediate position is zero and the stress is the largest. The position of the node is generally designed to be a fixed position, but the usual fixed position is designed to have a thickness greater than 3 mm, or the groove is fixed, so the fixed position does not necessarily have a zero amplitude, which causes some sound and part of the energy loss. The squeak is usually isolated from the other components by a rubber ring or shielded with a sound insulating material. Energy loss is taken into account when designing the amplitude parameters.
The main components of a set of ultrasonic welding systems include ultrasonic generators, transducers / amplitude modulators / welding heads, molds and frames
7, netting
Ultrasonic metal welding usually forms the surface of the welding surface, and the surface of the base is designed with a mesh. The purpose of the mesh design is to prevent the sliding of the metal parts and transfer the energy to the welding position as much as possible. The mesh design generally has a square, diamond, and strip mesh. Gold-clad metal and other metal-clad welding heads and bases are not required to design the texture. The size and depth of the mesh are determined according to the specific welding material requirements.
8, processing accuracy
Because the ultrasonic welding head works under high frequency vibration, it should maintain a symmetrical design to avoid the unbalanced stress and lateral vibration caused by the asymmetry of sound wave transmission. The welding head we use for welding uses the longitudinal direction of ultrasonic vibration. Passage, for the entire resonant system), unbalanced vibration can cause heat and breakage of the weld hair. Ultrasonic welding is applied to different industries and has different processing precision requirements. For particularly thin workpieces such as lithium ion battery pole pieces and tab welding, gold foil coating, etc., the processing precision is very high, all our processing equipment All CNC equipment (such as machining centers, etc.) are used to ensure that the precision of the machining meets the requirements.
9, the service life
The service life of a welding head is determined by two aspects: first, material, second, process
Materials: Ultrasonic welding requires metal materials to have good flexibility (small mechanical loss during sonic transmission), so the most commonly used materials are aluminum alloys and titanium alloys, but ultrasonic metal welding requires welding head wear resistance (required High hardness) makes the choice of materials more difficult, because hardness and toughness seem to be inherently opposite, which requires us to choose very high-demand materials. The high-quality steel materials we choose can solve this contradiction better. The effective life of the welding head is increased as much as possible.
Process: including processing technology and subsequent processing technology, the processing technology has been described in detail before, the subsequent processing includes heat treatment and parameter modification, based on the materials selected by our company, we have an original heat treatment process to ensure; in each welding After the head is completed, the parameters are measured and adjusted separately to ensure the product is produced.
10, metal phase melting top view of the mutual melting is for reference, the specific should be based on the experiment
Second, failure analysis
1. The heating horn has a certain heating phenomenon during work, which is caused by the mechanical loss of the material itself and the heat conduction of the weldment. Whether the welding hair heat is normal or not, when the load is not loaded (ie, does not touch the workpiece), the ultrasonic wave is continuously emitted for more than half an hour, and the temperature cannot exceed 50-70 ° C. If the heat is damaged, it proves that the welding head is damaged or the material is unqualified. Need to be replaced.
2. Whistling When the whistling of the welding head is working, the following reasons should be analyzed:
1 Is the mounting screw loose? 2 Is the weld head cracked? 3 The weld head is in contact with the object that should not be in contact.
2. Overload When the generator issues an overload alarm, it should be checked as follows:
1 No-load test, if the working current is normal, it may be that the welding head is in contact with the object that should not be touched or the parameter adjustment between the welding head and the welding seat is faulty.
2 When the no-load test is abnormal, first observe whether there is crack in the welding head, whether the installation is firm, then remove the welding head and carry out the no-load test to eliminate whether there is a problem with the transducer + horn, and eliminate it step by step. After eliminating the possibility of failure of the transducer + horn, replace the new horn to determine.
3 Sometimes there is a situation where the no-load test is normal, but it cannot work normally. It may be that the internal parts of the acoustic energy such as the welding head change, resulting in poor sound energy transmission. Here is a relatively simple judgment method: hand touch method. The normal working welding head or horn surface is very uniform when working, and the hand feels velvety smooth. When the sound energy is not smooth, the hand feels like bubbles or burrs. Exclusion methods are used to eliminate problematic parts. The same situation can occur when the generator is not normal, because normally the transducer input waveform should be a smooth sine wave, which can also occur when there are spikes or abnormal waveforms on the sine wave. At this time, another pruning acoustic energy element can be substituted for discrimination.
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