1. In order to obtain a perfect and repeatable fusion welding method, three main design directions must be followed:
(1) The two surfaces that are initially in contact must be small in order to concentrate the required energy and minimize the total energy required (ie, the joining time) to complete the fusion.
(2) The welding surfaces surrounding the connection interface must be uniform and in close contact with each other. If possible, the contact surfaces should be on the same plane, so that the energy conversion can be consistent.
( 3 ) Find suitable fixing and alignment methods, such as; plastic parts with sockets, steps or tongues, and the like.
2. The influence of plastic parts material on ultrasonic welding
Ultrasonic waves propagate in plastic parts, and plastic parts more or less absorb and attenuate ultrasonic energy, which has a certain impact on the effect of ultrasonic processing. , There is also the distinction of modulus. Generally speaking, the ultrasonic processing performance of plastics with high hardness and low melting point is better than that of plastics with low hardness and high melting point. Therefore, this involves the problem of the distance of ultrasonic processing.
3. The influence of processing conditions of plastic parts on ultrasonic welding
Different processing forms of plastic parts through injection molding, extrusion, or blow molding, and different processing conditions will have a certain impact on ultrasonic welding. The impact of the injection molding process:
The adjustment of the injection molding process parameters will lead to the following defects:
(1) Poor unity
(2) Surface damage
(3) Weight change
(4) Dimensional change (shrinkage, bending deformation)
4. The quality of ultrasonic welding can be obtained by controlling the following points:
(1) Support of the bottom mold
(2)Structure of plastic parts
(3) The contact surface between the welding head and the plastic part
(4) Welding material
(5) Position and design of welding line
(6) Smooth welding path
(7) The position and tightness of the upper and lower surfaces
(8) Size of the welding surface
5. Design of plastic parts Modern injection molding methods can effectively provide more perfect plastic parts for welding. When we decide to use ultrasonic welding technology to complete the fusion, the structural design of plastic parts must first consider the following points:
(1) Do you need watertight,
(2) Whether it is suitable for welding head processing requirements.
(3) The size of the weld (that is, the required strength should be considered)
(4) Do you need a perfect appearance?
(5) Avoid melting of plastic or overflow of composites
6. Humidity defects:
Humidity defects are generally formed during the production of striped or loose plastic parts. Humidity defects attenuate useful energy during welding, make the sealing position seep water, and prolong welding time. Therefore, plastic parts with high humidity should be dried before welding. Such as polyoxymethylene, etc.
(1) Release agent and impurities: release agent and impurities have a certain influence on ultrasonic welding. Although the solvent and impurities on the machined surface can be removed during ultrasonic processing, they should be removed as much as possible when sealing or high strength is required. In some cases, it is necessary to clean the plastic parts first.
(2) Shelf life: After the plastic parts are processed by injection molding, they are generally placed for at least 24 hours before welding to eliminate the stress and deformation of the plastic parts themselves. Plastic parts made of amorphous plastic by injection molding may not meet this requirement.
(3) Raw plastic: The strength of recycled plastic is relatively poor, and the adaptability to ultrasonic welding is also poor, so if recycled plastic is used, various design dimensions should be considered as appropriate.