The basic principle of ultrasonic welding process and ultrasonic welding machine
The basic principles of ultrasonic welding are divided into two categories: 1-The welding principle of ultrasonic welding machine, 2-The application principle of ultrasonic in plastic processing, as well as the parameters and adjustment methods of ultrasonic welding machine, etc., the four basic common sense of ultrasonic welding machine Knowledge points. Below we will explain in depth the basic knowledge of ultrasonic plastic welding machine:
Ultrasonic knowledge (1):
In order to obtain a perfect and repeatable fusion welding method, three main design directions must be followed: (1) The two initially contacted surfaces must be small in order to concentrate the required energy and minimize the total energy required (ie Time) to complete the splicing.
(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 as much as possible, so that the energy conversion can be kept consistent.
(3) Find a suitable method of fixing and alignment, such as; sockets, steps or tongue-and-groove of plastic parts.
Ultrasonic knowledge (two):
The influence of plastic parts materials on ultrasonic welding
Ultrasonic waves propagate in plastic parts. Plastic parts more or less absorb and attenuate ultrasonic energy, which will have a certain impact on the ultrasonic processing effect. Plastics are generally divided into non-crystalline materials. According to the hardness, there are hard rubber and soft rubber. , There is also the distinction of modulus. In layman's terms, 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 issue of the distance of ultrasonic processing.
Ultrasonic knowledge (3):
Influence of processing conditions of plastic parts on ultrasonic welding
Plastic parts undergoing different processing forms such as injection molding, extrusion or blow molding, as well as different processing conditions, will form factors that have a certain impact on ultrasonic welding. There are two major reasons:
(1) The impact of the injection molding process:
The adjustment of the parameters of the injection molding process will cause the following defects:
1 Poor uniformity
2 surface damage
3 weight change
4Dimensional changes (shrinkage, bending deformation)
Ultrasonic knowledge (four):
The quality of ultrasonic welding can be obtained by controlling the following points:
(1) Support of bottom mold
(2) The structure of plastic parts
(3) Contact surface between welding head and plastic parts
(4) Welding material
(5) Location and design of welding line
(6) Smooth welding path
(7) The position and tightness of the upper and lower surfaces
(8) The size of the welding surface
Ultrasonic knowledge (5)
The design of plastic parts. Modern injection molding methods can effectively provide 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) Whether it needs to be watertight and airtight
(2) Whether it is suitable for welding head processing requirements
(3) The size of the weld (that is, the required strength must be considered)
(4) Do you need a perfect appearance
(5) Avoid plastic melting or overflow of synthetics
Ultrasonic knowledge (6):
Humidity defects: Humidity defects are generally formed in the process of making streaks or loose plastic parts. Humidity defects attenuate useful energy during welding, cause water seepage at the sealing position, and lengthen the welding time. Therefore, plastic parts with high humidity should be dried before welding. deal with. Such as polyoxymethylene and so on.
(1) Release agent and impurities: Release agent and impurities have a certain effect on ultrasonic welding. Although the solvent and impurities on the processed surface can be shaken away during ultrasonic processing, it 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 through injection molding do not meet this requirement.
(3) Recycled plastics: The strength of recycled plastics is relatively poor, and the adaptability to ultrasonic welding is also poor. Therefore, if recycled plastics are used, various design dimensions should be considered as appropriate.
