Because many new companies have been born in the market due to the epidemic in recent years to sell ultrasonic plastic welding equipment, but there are no good solutions to the common problems of ultrasonic operations. Therefore, the editor is commissioned by experts engaged in the field of ultrasonic research. This article is presented for the reference of the majority of users. If there is anything inappropriate in the article, please give me more guidance.
1. The strength cannot meet the desired standard. Of course, we must understand that the strength of ultrasonic welding can never reach the strength of one-piece molding, it can only be said to be close to the strength of one-piece molding, and the required standard of welding strength must depend on the cooperation of multiple items. What are these cooperations? ※Plastic material: The result of mutual welding between ABS and ABS must be stronger than that of ABS and PC, because the melting points of the two different materials will not be the same, and of course the strength of welding cannot be the same, although we discuss Can ABS and PC be welded together? Our answer is that it can definitely be welded, but is the strength after welding what we want? That's not necessarily the case! On the other hand, what if ABS melts with nylon, PP, and PE? If the ultrasonic HORN emits heat energy of 150 degrees instantly, although the ABS material has been melted, the nylon, PP, and PE are only softened. We continue to increase the welding parameters. At this time, nylon, PP, and PE have reached the ultrasonic welding temperature, but the ABS material has been resolved into another molecular structure!
Three conclusions can be drawn from the above discussion:
1. The welding strength of plastic materials with the same melting point is stronger.
2. The greater the difference in the melting point of plastic materials, the smaller the welding strength.
3. The higher density (hard) plastic material will have higher welding strength than the lower density (high toughness).
2. There are scars or cracks on the surface of the product. In ultrasonic plastic welding operations, it is common to have product surface scars, joint breaks or cracks.
Because there are two situations in ultrasonic operations:
1. High heat energy directly contacts the surface of plastic products
2. Vibration conduction.
Therefore, when ultrasonic vibration acts on plastic products, the surface of the product is prone to burns, and plastic columns or holes with thinner walls within 1m/m are also prone to rupture. This is a prerequisite phenomenon for the operation of ultrasonic plastic welding machines. avoidable. On the other hand, due to the lack of ultrasonic output energy (extension table and HORN upper mold), it takes a long time to weld when the vibration and friction energy is converted into heat energy, so as to make up for the lack of output power by accumulating heat energy. This kind of welding method does not achieve vibration and friction heat energy in an instant, but needs to accumulate heat energy by welding time. Even if the melting point of the plastic product reaches the welding effect, this will cause the heat energy to stay on the product surface for too long, and the accumulated temperature and Pressure will also cause burns, snapping or rupture of the product. Therefore, at this time, it is necessary to consider matching factors such as power output (number of segments), welding time, and dynamic pressure to overcome this lack of operation.
Solution:
1. Reduce stress.
2. Reduce the delay time (early oscillation).
3. Reduce welding time.
4. Cover with medium (such as PE bag).
5. Die fixture surface treatment (hardened or chrome-plated).
6. Reduce the number of machine segments or reduce the expansion ratio of the upper die.
7. For products that are easy to crack or break, the jig should be made of cushioning, such as soft resin or covered cork (this does not affect the welding strength).
8. For products that are easy to break, add an R angle at the right angle.
3. The product is distorted and deformed. We attribute this deformation to three reasons:
1). The angle or radian of the body and the object to be welded or Gein cannot match each other.
2). The inner thickness of the product (within 2m/m) and the length exceeds 60m/m.
3). The product is deformed and twisted due to injection molding pressure and other conditions.
Therefore, when our products are deformed by ultrasonic operation, it seems to be the cause of ultrasonic welding from the surface, but this is only a result. Any factors before the plastic products are not welded will form the result after welding. If the main cause is not discussed, it will take a lot of time to deal with the problem of not prescribing the right medicine, and in the ultrasonic indirect conduction welding operation (non-direct welding), the pressure below 6kg cannot change the plastic's flexibility and inertia. So don't try to use strong pressure to change the deformation before welding (the maximum pressure of the welding machine is 6kg), including forced extrusion with mold fixtures. Perhaps we also fall into a blind spot, which is to explore the cause of deformation from the surface, that is, it is invisible to the naked eye before welding, but after the completion of ultrasonic welding, the deformation is obviously found. The reason is that before the product is welded, due to the existence of the fuse line, it is difficult to find the accumulated errors of various angles, radians and residual materials of the product itself, but after the completion of ultrasonic welding, it appears visible to the naked eye. out of shape.
Solution:
1. Reduce the pressure (preferably below 2kg).
2. Reduce the ultrasonic welding time (reduce the strength standard).
3. Increase hardening time (at least 0.8 seconds above).
4. Analyze whether the ultrasonic upper and lower molds can be adjusted locally (if not necessary).
5. Analyze the main causes of product deformation and make improvements.