1. Misunderstanding of welding workpiece
Ultrasonic energy explodes instantaneously, the welding line should be formed into points or lines and the transmission distance 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 wrong understanding. When the instantaneous energy is generated, the larger the joint area, the more severe the energy dispersion, the worse the welding effect, and even the welding is impossible. 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 as the best condition, and the wall thickness of the workpiece should not be less than 2mm, otherwise it cannot be welded well, especially for products that require watertightness.
2. Misunderstanding of workpiece material
Ultrasonic welding machines have requirements on the materials of the welded workpieces. Not all materials can be welded. Some people think that any material can be welded. This is a big misunderstanding. Some different materials can be welded well, and some can be welded. Some are incompatible. 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 no longer suitable for ultrasonic welding. Because ultrasound melts the molecules of the workpiece instantaneously, the basis of judgment is within 1-3. If the welding is not good, you should choose other welding processes, such as hot plate, spin melting, vibration and friction. Generally speaking, ABS material is the easiest to weld because of its low melting point and hardness. On the contrary, nylon is the most difficult to weld.
3, Mistakes in ultrasonic selection
How much output power to use, oscillation frequency, and 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 airtight. Myth is that the greater 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 a regular ultrasonic production plant. If possible, it is best to communicate with the manufacturer on site, and do not blindly listen to the misleading of some informal ultrasound sales staff. At present, the companies that produce related equipment are particularly complex, most of which are family workshops, which copy the circuit rigidly, and seem to understand the working principle. The copied 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 during medium and high power operation, and the product qualification rate is low. Sometimes the equipment is damaged. Such as the power transformer of the transducer, the parameters of the magnetic materials used cannot be measured, magnetic saturation magnetic flux density (Bs), magnetic induction intensity (Bm), effective magnetic permeability (Ue), residual magnetic flux density (Br), coercivity (A / M) etc. The winding process is quite complicated, and these home-style workshops cannot be done. Therefore, to buy ultrasound, it is best to understand the company's situation first. Only in this way can unnecessary trouble be reduced in the future.
4, misunderstanding of ultrasonic output power
The output power of the ultrasonic wave is the same as the diameter and thickness of the piezoelectric ceramic sheet, the material, and the design process. The transducer is shaped and the maximum power is shaped. Measuring the output energy is a complicated process. It ’s not that the larger the transducer, the more power tubes used in the circuit, the greater the output energy. It must require a fairly complex amplitude measuring instrument to accurately measure its amplitude. Coupled with the misleading of the sales staff, it gives consumers a wrong understanding that the amount of electrical energy consumed does not reflect the size of the output ultrasonic power. If the longitudinal energy generated is low and the current consumption is large, it can only explain the efficiency of the equipment, without power. Say.
5. Misunderstanding in welding principle
A considerable number of people who have been engaged in ultrasonic welding for many years have a misunderstanding about the transmission of ultrasonic energy. It is believed that the welding of sound waves on the contact surface is actually a misunderstanding. The true welding principle is that after the transducer converts electrical energy into mechanical energy, it passes through the workpiece The material molecules conduct, and the sound wave conducts sound resistance in solids is much smaller than that in 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. The temperature first reaches the melting point of the workpiece, and then 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 Ohm's law.
6, Misunderstanding of welding structure
Different types of ultrasonic molds (Horn), the shape of the workpiece determines the shape of the mold, but the size and radian 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 efficiency, life span, product qualification rate of the mold, and directly burns out the generator in severe cases. The material of the mold is generally magnesium aluminum 7075, and some people use inferior materials to reduce costs. Regular mold manufacturers have a set of strict inspection procedures for incoming materials, and the processed dimensions are processed after computer software simulation and verification. Quality is guaranteed. These processes cannot be done by general workshops. Without reasonable design, the molds produced will not have obvious reaction problems when welding small workpieces. Various disadvantages will occur when high power is used. In severe cases, directly damage the components