When ultrasonic waves act on the contact surface of the thermoplastic, tens of thousands of high-frequency vibrations per second are generated. This high-frequency vibration reaches a certain amplitude, and the ultrasonic energy is transmitted to the weld zone through the upper weldment. The sound resistance at the interface of the weldment is large, so local high temperature will occur, and due to the poor thermal conductivity of the plastic, it can not be dissipated in time and gather in the weld zone, causing the contact surfaces of the two plastics to melt rapidly, plus a certain pressure, so that It is integrated into one. When the ultrasonic wave stops, let the pressure last for a few seconds to make it solidified, thus forming a strong molecular chain. For the purpose of welding, the strength of the ultrasonic plastic welding machine can be close to the strength of the raw material.
The quality of ultrasonic plastic welding depends on the amplitude of the transducer horn. Three factors, such as the pressure P and the welding time. The welding and the welding head pressure P can be adjusted and the amplitude is び. It is determined by the transducer and the horn.
The energy required for its welding
These three quantities should have an appropriate value for each other. When the energy E exceeds an appropriate value, the amount of melting of the plastic is large, and the welded material is easily deformed. If E is small, it is not easy to weld. P should not be too large. This optimum pressure is the product of the side length of the welded portion and the optimum pressure per 1 mm of the side heald. When welding styrene, AS, ABS and other plastics, the optimum pressure is about 1.47-2.94 N/mm2.
Although there is a rough calculation about the welding conditions (power and pressure), but because of the type of welding machine or the nature and shape of the plastic, there is only one general criterion. Ultrasonic output power versus pressure curve. Among them, the amplitude of the horn is used as a parameter.
The conclusion is that the rigidity of the reflective sonotrode suitable for the workpiece is effective in reducing the time and amplitude required to obtain high quality welding.
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