Ultrasonic spot welding joins two thermoplastic parts at localized points without a preformed hole or energy director. It produces a strong structural weld and is especially suitable for large parts or parts with complicated geometry or hard-to-reach joining surfaces. The horn has a pilot tip in spot welding, which melts through the top part and into the bottom portion to a predetermined depth when ultrasonic vibrations are applied. When vibrations cease, the melt from both parts flows together, forming a weld with the top side having a raised ring produced by the welding tip. The bottom layer of a spot welding joint has a smooth appearance. Spot welding can be performed with hand-held guns, single- or double-headed bench welders.
The power supply's role is to convert the incoming line voltage (at 50 or 60Hz) into a new frequency. This electrical energy is then sent to the converter, which, as the name implies, converts the electrical energy into mechanical vibrations. The converter consists of piezoelectric ceramic discs, which expand and contract at the supplied electrical energy rate. The oscillations' magnitude is referred to as amplitude, a term that becomes very important when specifying an ultrasonic system for a given application. The vibrations are transmitted through the booster, which typically increases the amplitude by a predetermined multiple, also known as gain. Finally, the booster’s output amplitude is transmitted through the horn, where it can then be delivered to the plastic parts.
Table of Contents
Ultrasonic welding machine composition
An ultrasonic generator (power supply)
hcsonic 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 a linear, mechanical movement. This conversion occurs using piezoelectric ceramic disks that expand when a voltage is applied.
An ultrasonic booster
Ultrasonic booster and round flange 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)
The ultrasonic welding horn is a custom-made tool that is engineered to vibrate at a specific frequency. These tools are painstakingly designed using computer modeling technology for optimum performance and longevity. Ultrasonic devices must be tuned to match the frequency of the system. This tuning procedure requires considering the horn’s mass, length, and geometry. The standard tool head diameter is 10mm.
Longer service life
Transducer prestress
All piezoelectric transducers for ultrasonic welding are of the Langevin type — i.e., one or more piezoceramics that are mechanically compressed (prestressed) between a front driver and a back
driver.
Transducer cross-section
Transducer Relative axial amplitude because piezoceramics are weak in tension, a static compressive prestress must be applied to prevent the piezoceramics from ever experiencing tensile stresses when the transducer vibrates ultrasonically. The prestress also assures that the piezoceramic interfaces make good contact so that the acoustic waves are transmitted well with minimum loss. We use the most convenient center screw design.
A specific prestress can be obtained by tightening the transducer center screw to tighten the transducer. The traditional method is to use a torque wrench for drawing, but this parameter is
affected by many factors and often has deviations.
When the tightening of the ultrasonic transducer is insufficient, its impedance is large, which will cause serious heat generation; when the tightening is excessive, it is easy to cause problems such as damage to the ceramic sheet (crystal crack) and durability. The transducer is the most important part of ultrasonic welding equipment. So it is essential to tighten the transducer and obtain the best prestress accurately.
Piezoelectric ceramic sheet
Piezoceramics are typically classified as "soft" or "hard." Hard piezoceramics are used for power applications. Among hard piezoceramics, there are two basic types, generally designated as PZT4 and PZT8 (PZT stands for lead-zirconate-titanate of which the piezoceramics are composed). Different manufacturers may have their designations for these types, but the general performance is similar. Our device uses PZT8 piezoelectric ceramics, which has a better relative performance.
Advantages of ultrasonic spot welding
- Does not need an external heat source: Ultrasonic welding's primary advantage is that it doesn’t need an external heat source. The heat is self-generated between the materials.
- Fast: Since vibrations' frequency is very high, and ultrasonic welding is one of the quickest welding methods available in the industry.
- Possibility of automation: Ultrasonic welding being uncomplicated in many ways, is easy to automate. The ultrasonic machine comes with sensors that continuously monitor the temperatures.
- Clean and robust joint: The contact surfaces melt/fuse upon welding, and it produces a very clean and full joint.
Ultrasonic welding has many advantages when compared to traditional welding technologies. Many industries use ultrasonic welding due to these specific combinations of merits.
Application of ultrasonic spot welding
Ultrasonic welding is an eco-friendly process that takes seconds, consumes very little energy, and reduces costs while maintaining high quality. The equipment fuses contact points on cell phones and other consumer electronics that are generally inaccessible with other welding methods. These techniques can be adapted to a wide range of commercial and industrial applications. In the food industry, the ultrasonic welding process is used to create a hermetic seal. It can fasten blister packs and facilitate various products, including toys, disposable lighters, pipettes, and intravenous catheters.
Ultrasonic welding is commonly used in the plastics, aerospace, and automotive industries to join similar materials. It is advantageous in the production of medical products. Since the process does not introduce exhaust or other contaminants and the welds do not degrade, the manufacturing equipment can be used in a clean-room environment.
Ultrasonic spot welding tips
Ultrasonic welding is very effective at sealing or welding plastics. However, you cannot weld all types of plastics. Like metals, plastics also have different styles. And it is essential to ensure that the plastics to be welded are chemically compatible. If you try welding polyethylene and polypropylene, they may melt together, but there will be no chemical bond. A chemical bond is essential for creating healthy weld joints. Another factor to keep in mind while welding any material through ultrasonic welding is maintaining a uniform contact area.
| Attributes | Parameter | Attributes | Parameter |
|---|---|---|---|
| Brand | HCSONIC | Item Model | WW2803L |
| Maximum Power output | 300W | Frequency | 28KHZ |
| Maximum Amplitude | 3µm | Working model | Continuous, intermittent |
| Weldable materials | Thermoplastic materials | Welding Head Material | Al, Steel |
| Welding Head diameter | 10mm | Driven Type | Electric |
| Technical Support | Video, mail, phone | Warranty | One year, except the horn. |
| Full Set Weight | 4.5KG | Place of Origin | China |
Production time: within 15 days or according to customer requirements.Shipping method: DHL, FedEx, UPS, TNT, sea, or air.
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