Six common problems of ultrasound
Date：2020/10/24 Views：5015 【BACK】
1. Process misunderstanding of welding workpiece
Ultrasonic energy is instantaneous. The welding line should be a point or line and the transmission distance must be in line with 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 wrong understanding. When the instantaneous energy is generated, the larger the joint area, the more serious the energy dispersion, the worse the welding effect, or even the failure to weld. Ultrasonic waves propagate longitudinally, and 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, which is a better state, and the wall thickness of the workpiece should not be less than 2mm, otherwise it cannot be welded well, especially for products that require water and air tightness.
2. Misunderstanding of workpiece material
Ultrasonic welding machines have requirements for the material of the workpiece to be welded. 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, and some can basically be welded. Some are insoluble. The melting point of the same material is the same, and it can be welded in principle. But when the melting point of the welded workpiece is greater than 350 degrees, it is not suitable for ultrasonic welding. Because ultrasound melts the molecules of the workpiece in an instant, the judgment basis is within 1-3. If the welding cannot be performed well, other welding processes should be selected, such as hot plate, rotary melting, vibration and friction. Generally speaking, ABS material is easy to weld because of its low melting point and hard hardness. On the contrary, nylon is more difficult to weld.
3. Misunderstanding of ultrasonic selection
How much output power to use, the oscillation frequency, and the amplitude range should be considered according to the material of the workpiece, the area of the welding wire, whether there are electronic components in the workpiece, and whether it is air tight. Misunderstanding that the greater the power, the better. This is also a misunderstanding. If you don’t know much about ultrasound. Need to consult a regular ultrasonic production plant engineering and technical personnel. If possible, you need to communicate with the manufacturer on-site, and do not blindly follow the misleading of some informal ultrasound sales staff. At present, the companies that produce related equipment are particularly complex, most of which are family-style workshops, which mimic circuits mechanically and seem to understand the working principles. The imitated equipment has a fatal flaw. One is that the quality of the purchased raw materials cannot be guaranteed, and the second is that the core technology of the production process is not mastered. The equipment is often unstable in medium power and high power work, and the product qualification rate is low. Sometimes the equipment is damaged. Such as transducer power transformer, the magnetic material parameters used cannot be measured, magnetic saturation magnetic flux density (Bs), magnetic induction intensity (Bm), effective permeability (Ue), residual magnetic flux density (Br), coercive force (A/M) etc. The winding process is quite complicated, and these family workshops cannot do it. Therefore, to buy ultrasound, you need to know the company's situation first, don't blindly follow the salesperson's praise, and don't just ask for the price. Only in this way can we reduce unnecessary troubles in the future.
4. Misunderstanding of ultrasonic output power
The ultrasonic output power is the same as the diameter and thickness of the piezoelectric ceramic sheet, material, and design process. When the transducer is shaped, the power is also shaped. Measuring the output energy is a complicated process. It’s not that the larger the transducer, the more power tubes the circuit uses, the greater the output energy. It requires a very complicated amplitude measuring instrument to accurately measure its amplitude. Since most users don’t know much about supersonic waves, add The misleading of the sales staff in Shanghai gave consumers a wrong understanding that the amount of electrical energy consumed does not reflect the size of the output ultrasonic power. For example, the low longitudinal energy produced but the large current consumption can only show that the efficiency of the equipment is low, and there is no high power. .
5. Misunderstanding of welding principle
Quite a few people who have been engaged in ultrasonic welding for many years have a misunderstanding about the transmission of ultrasonic energy. It is a misunderstanding that sound waves are welded on the contact surface. The real welding principle is that after a transducer converts electrical energy into mechanical energy, it passes through the workpiece. The material molecules conduct, and the acoustic resistance of sound waves in solids is much smaller than that in the air. When the sound waves pass through the joints of the workpiece, the acoustic resistance in the gap is large, and the heat generated is quite large. The temperature first reaches the melting point of the workpiece, and then A certain pressure is applied to weld the seams, and the other parts of the workpiece will not be welded due to low acoustic resistance and low temperature. The principle is similar to Ohm's law.
6. Misunderstanding of welding structure
There are many types of ultrasonic molds (Horn), and the shape of the workpiece determines the shape of the mold, but the size, curvature, and material of each part 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 mold's efficiency, life, and product qualification rate, and in severe cases, it will directly burn the generator. The material of the mold is generally magnesium-aluminum 7075, and some people use low-quality materials to reduce costs. Regular mold manufacturers have a set of strict inspection procedures for incoming materials, and the processing dimensions are processed after computer software simulation and verification. Quality is guaranteed. These processes cannot be done in general workshops. Molds made without reasonable design will not have obvious reaction problems when welding small workpieces, and various drawbacks will appear when high power is applied. In severe cases, the components will be directly damaged.
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