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Common misunderstanding of ultrasonic welding

2019-08-30 10:10:39

Common misunderstanding of ultrasonic welding

 

1. Mistaken material of the workpiece

Ultrasonic welding is required for the material of the welded workpiece. Not all materials can be welded. Some people think that any material can be welded. This is a big misunderstanding. Some materials can be welded well, some can be welded, and some are Not fused. The melting point between the same material is the same, and in principle it can be welded. However, when the melting point of the welded workpiece is greater than 350 degrees, it is not suitable for ultrasonic welding. Because the ultrasonic is instantaneously melting the workpiece molecules, the judgment is based on 1-3 seconds, and the welding is not good. Other welding processes should be selected, such as hot plate welding equipment, rotary welding machine, vibration friction welding scheme. What kind of material is suitable for ultrasonic welding? Generally speaking, ABS material is the easiest to weld because the melting point is low and the hardness is hard. On the contrary, nylon is the most difficult to weld.

 

2. Process misunderstanding of welding workpiece

Ultrasonic energy is instantaneously erupted, and the welding line should be in points or lines and the distance to be transmitted must conform to the ultrasonic welding method. Some people think that as long as it is a plastic material, no matter how the joint surface can be welded well, this is a misunderstanding. When the instantaneous energy is generated, the joint area is larger, the energy dispersion is more serious, the welding effect is worse, and even the welding cannot be performed. Ultrasonic waves are transmitted longitudinally, the energy loss is proportional to the distance, and the long distance should be controlled within 7.5 cm. The welding line should be controlled between 0.3-0.8mm for the best condition. The wall thickness of the workpiece should not be lower than 2mm, otherwise it will not be welded well, especially for products requiring water tightness.


 

3. Ultrasonic output power misunderstanding

The output power of the ultrasonic wave is determined by the diameter and thickness of the piezoelectric ceramic piece, the material, the design process, the shape of the transducer, and the maximum power is also determined. Measuring the output energy is a complicated process. Not the larger the transducer, the more power the circuit uses, the greater the output energy. It must have a fairly complex amplitude measurement instrument to accurately measure its amplitude. Because most users don't know much about the super-wave knowledge, plus The misleading of the sales staff gives the consumer a wrong understanding. The amount of power consumed does not reflect the magnitude of the output ultrasonic power. For example, the longitudinal energy is low, and the current consumption is large, which can only indicate the efficiency of the equipment. 

 

4. Ultrasonic selection misunderstanding

How much output power, oscillation frequency, and amplitude range are used should be considered according to the material of the workpiece, the area of the wire bond, whether there are electronic components in the workpiece, whether it is airtight or not. I mistakenly think that the bigger the power, the better. This is also a misunderstanding. If you don't know much about ultrasound. It is best to consult the engineering and technical personnel of the regular ultrasonic production plant. If you have the conditions, it is best to communicate with the manufacturer on site, and do not blindly follow the misleading of some irregular ultrasound sales personnel. At present, the companies that produce related equipment are particularly complicated, and most of them are family-style workshops, which are used to copy and reproduce the circuit, and do not understand the working principle. The imitation of the device has a fatal flaw. One is that the quality of the raw materials purchased cannot be guaranteed, and the core technology of the second production process is not mastered. The equipment often performs unstable in medium power and high power operation, and the product qualification rate is low. Sometimes the device is damaged. For transducer power transformers, the magnetic material parameters used cannot be measured, magnetic saturation flux density (Bs), magnetic induction (Bm), effective permeability (Ue), residual flux density (Br), coercivity (A/M), etc., the winding process is quite complicated, and these family-style workshops cannot do it. So to buy ultrasound, it is best to first understand the company's situation, do not blindly obey, and do not just price.

 

5. Misunderstanding in the principle of welding

A considerable number of people engaged in ultrasonic welding for many years have a misunderstanding about ultrasonic energy transmission. It is a misunderstanding that the sound wave is welded on the contact surface. The real welding principle is that the transducer converts electrical energy into mechanical energy and passes through the workpiece. The matter molecules conduct, the acoustic impedance of the acoustic wave in the solid is much smaller than the acoustic resistance in the air. When the sound wave passes through the joint of the workpiece, the acoustic resistance in the gap is large, and the generated thermal energy is quite large, and the temperature first reaches the melting point of the workpiece. With a certain pressure, the seam is welded, and the other parts of the workpiece will not be welded due to the low acoustic resistance and low temperature. The principle is similar to Om's law.

 

6. Misunderstanding of the welded structure

The Horn type is various, the shape of the workpiece determines the shape of the mold, but the size and curvature of each part, the material must be strictly calculated, some people mistakenly think that it is just a metal block. Whether the design is reasonable or not directly affects the efficiency of the mold, the life, the qualified rate of the product, and directly burns the generator when it is serious. The material of the mold is generally magnesium magnesium 7075, and some people use inferior materials to reduce costs. Regular mold manufacturers have a strict inspection procedure for the feeding, and the processing dimensions are processed by computer software simulation and verification. Quality is guaranteed. These processes are generally not possible in the workshop. If the mold is not properly designed, the reaction problem is not obvious when welding small workpieces. When there is high power, various drawbacks will occur. Damage to components directly in severe cases.



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