Basic principles and advantages of ultrasonic handheld spot welding machine
Ultrasonic spot welding machine actually belongs to the category of ultrasonic welding. It uses ultrasonic waves to generate high-frequency vibration to weld two materials, metal or plastic, together. For hot-formed parts without assembly contours, or parts whose geometry and actual conditions exclude the possibility of standard welding operations, ultrasonic spot welding is relatively more suitable for processing.
Spot welding can be used for ultrasonic strong spot welding on soft plastic sheets such as ABS, polyethylene, polypropylene, and PVC. The specially designed projection head is used to enhance the welding strength and appearance. Ultrasonic spot welding replaces adhesives, rivets, staples and other mechanical fasteners. This process is used to assemble trailer bodies, automotive defroster pipes, furniture and other large thermoplastic parts. Using portable handheld tools and a multi-head automation system, many welds can be performed at the same time.
Principle of Welding
Ultrasound is a mechanical vibration, similar to the vibration produced by musical instruments. These vibrations are called ultrasonic waves because their frequency is higher than human hearing (greater than 16 kHz). In the acoustic component, these pressure waves are generated by a generator. This will send alternating current at the same frequency as the converter (or transducer). Then, a transducer made of piezoelectric ceramics converts this energy into mechanical vibration. Then, mechanical vibration will generate thermal friction, which will stimulate the molecules of the material being welded to start moving. Ultrasonic energy will melt the contact points between the two parts, thereby forming a joint, allowing the parts to bond quickly.
The spot welding machine is suitable for those components that do not need to weld the entire welding path at the same time. It is light in weight and easy to use, and can be used in outdoor scenes. Spot welding machine has high versatility, flexibility and cost-effectiveness, so it still has strong competitiveness in various welding fields.
Welding advantages
Welding process: Monitoring ultrasonic welding through time, energy, power and height limits, and real-time detection of the entire welding process to maximize the efficiency of the entire welding process and minimize the energy consumption of production.
Cost saving and environmental protection: The entire welding process is clean and pollution-free, because any harmful solvents or adhesives will not be used during the welding process, and the product itself will not be damaged, avoiding some of the problems of traditional welding and bonding processes , Save welding cost. Due to its complete electrical characteristics, this technology does not require high-level maintenance.
Speed: The typical welding cycle is within 0.5 seconds. Compared with other welding methods, the welding speed is faster. This welding technique is much faster than traditional adhesives or solvents. The cooling time is very fast, and the workpiece does not need to be left in the tool for a long time to dry or solidify the welded joint.
Easy to use: The general ultrasonic spot welding machine or spot welding gun equipment is a small machine, which is relatively light to operate and does not require high manual technology. It is convenient to store after use and does not take up a lot of space. Ergonomics and lightweight handheld probe can reduce operator fatigue. The lightweight system with integrated handle makes the device easy to move and easy to move in the factory.
High welding accuracy: high-precision thrust control and highly accurate welding depth control ensure the overall welding quality and avoid weak welding. Ensure a certain welding quality and avoid burning or burning of materials.
Equipment composition
Ultrasonic handheld spot welding equipment includes flow control valve, transducer, ultrasonic generator and welding head. Compared with ordinary welding equipment, the spot welding machine is lighter and suitable for welding work that needs to shift scenes.
Ultrasonic generator
The generator converts the electrical energy from the single-phase power supply into the correct frequency and voltage to convert the transducer into mechanical vibration. The microprocessor unit controls the welding cycle and feeds back key welding information to the user through the user interface. The user interface also allows the operator to enter the required welding parameters. The main function of the ultrasonic generator is to convert 50-60 Hz electric energy (5000 watts) into 20-40 kHz high-frequency electric energy. The frequency widely used in ultrasonic welding applications is 20 kHz.
Transducer
The transducer is also called a converter, which converts the electrical energy from the generator into mechanical vibration for the welding process. It consists of many piezoelectric ceramic discs sandwiched between two metal blocks (usually titanium). There is a thin metal plate between each disc, which forms an electrode. When the sine wave electric signal is fed to the transducer through the electrode, the disc will expand and contract, resulting in an axial peak-to-peak movement of 15 to 20 μm. The transducer is a precision device and should be handled with care during the welding process. Once the element is damaged, the transducer will not work.
Horn
The reinforced part of the horn has two functions, mainly to amplify the mechanical vibration generated at the tip of the transducer and transmit it to the welding head. The second main purpose is to provide a place to install the stack on the welding press. When the transducer applies ultrasonic energy, the horn expands and contracts. Like the other elements in the welding stack, the horn is a tuning device, so it must resonate at a specific frequency in order to transfer ultrasonic energy from the transducer to the welding head. In order to function successfully, the horn must be half the wavelength of the ultrasonic wave in the material from which the ultrasonic wave is made, or a multiple of that length. Usually, it is half the wavelength.
Welding head
The welding head is a component in the welding stack that provides energy to the parts to be welded. The design of the welding head is essential for successful welding. The welding head is also a tuning device, and in most applications, it can also provide mechanical gain. It is usually made of aluminum or titanium. Aluminum fillets are often used in small batch applications because this material may cause wear. Some fillets have particularly hardened tips to reduce wear during welding. As with the horn element, the length of the welding angle must be half of the wavelength of the ultrasonic wave in the material of which it is made, or a multiple of this length. This will ensure that the fillet end has sufficient amplitude for welding. The amplitude is usually between 30 and 120 μm.
