The ultrasonic spot welder belongs to the category of ultrasonic welding, where two materials, metal or plastic, are welded together using high-frequency vibrations generated by ultrasound. For thermoformed parts without assembly contours or features where geometry and physical conditions preclude the possibility of standard welding operations, ultrasonic spot welding is relatively more suitable for processing.
Spot welding can be performed on soft plastic sheets such as ABS, polyethylene, polypropylene, and PVC with ultrasonic power spot welding. Specially designed projection heads are used to enhance weld strength and appearance. Ultrasonic spot welding replaces adhesives, rivets, staples, and other mechanical fasteners. The process is used to assemble trailer bodies, automotive defroster pipes, furniture, and other large thermoplastic parts. Many welds can be performed simultaneously using portable handheld tools as well as multi-head automation systems.
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The principle of spot welding
Ultrasound is a mechanical vibration, similar to that produced by a musical instrument. These vibrations are called ultrasonic waves because they have a frequency higher than the hearing of the human ear (greater than 16 kHz). In an acoustic assembly, these pressure waves are generated by a generator. This sends an alternating current of the same frequency as the transducer (or transducer). The transducer, made of piezoelectric ceramic, then converts this energy into mechanical vibrations. The mechanical vibrations then create thermal friction, which excites the material's molecules being welded to start moving. The ultrasonic energy melts the contact points between the two parts, thus creating a joint that allows the parts to be bonded quickly.
The spot welder is suitable for those components that do not require the entire welding path to be welded simultaneously, is inherently lightweight and easy to use, and can be used in outdoor scenarios. Spot welders are highly versatile, flexible, and cost-effective, and therefore remain highly competitive in various welding applications.
The advantages of ultrasonic spot welding
- Welding process: Ultrasonic welding is monitored by time, energy, power, and height limits, and the entire welding process is detected in real-time, maximizing the efficiency of the entire welding process and minimizing the energy consumed in production.
- Cost-saving and environmental protection: The whole welding process is clean and pollution-free because no harmful solvents or binders are used in the welding process, and no damage is done to the product itself, avoiding some of the problems of traditional welding and bonding processes and saving welding costs. The technology does not require a high level of maintenance due to its complete electrical characteristics.
- Speed: Typical welding cycles are within 0.5 seconds, which is faster compared to other welding methods. This welding technique is much faster than traditional adhesives or solvents. The cooling time is speedy, and the workpiece does not have to be left in the tool for long periods of time to dry or cure 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 skills. Easy to collect after use, does not take up a lot of space. The ergonomic and lightweight handheld probe reduces operator fatigue. The lightweight system with an integrated handle makes the unit easy to move around the factory.
- High welding accuracy: High precision thrust control and highly accurate weld depth control guarantee overall weld quality and avoid unsound welds—guaranteed certain welding quality to avoid material blackening or burning.
The composition of ultrasonic handheld spot welder
The ultrasonic handheld spot welder equipment includes a flow control valve, transducer, ultrasonic generator, and welding head. Compared with ordinary welding equipment, the spot welder is more lightweight and suitable for welding jobs that require transfer scenarios.
An ultrasonic generator (power supply)
The ultrasonic generator converts the 110VAC or 220VAC electrical supply current into a high frequency, high voltage electrical signal.
An ultrasonic converter (transducer)
The ultrasonic converter utilizes the high-frequency electrical signal from the generator and converts it into linear, mechanical movement. This conversion occurs through the use of piezoelectric ceramic disks that expand when a voltage is applied.
An ultrasonic booster
The ultrasonic booster is a tuned component that mechanically adjusts the amount of linear vibratory movement from the converter to the required level for the specific application to produce optimal welding performance. The booster also provides a safe, non-vibrating location to clamp onto the welding tools.
An ultrasonic welding tool (horn/sonotrode)
The ultrasonic welding horn is a custom-made tool engineered to vibrate at a specific frequency. These tools are painstakingly designed using computer modeling technology for optimum performance and longevity. Ultrasonic tools must be tuned to match the frequency of the system. This tuning procedure requires consideration of the horn’s mass, length, and geometry.