Ultrasonic welding machines often encounter some undesirable problems when welding products, which affects the production process and product quality. How to solve the problem caused by the ultrasonic plastic welding equipment in the welding process of the product?
1. Requirements for raw materials for ultrasonic welding
▶ Polymer structure
The process of bonding monomers together is called "polymerization," and polymers fall into two broad categories: thermoplastic and thermoset. After the thermoplastic material is thermoformed, it can be softened and molded again.
What the base experiences is only a change in state - this property determines the adaptability of the ultrasonic compression of the thermoplastic material. Thermosetting materials are produced by irreversible chemical reactions. Reheating or pressurization does not soften the formed thermosetting products. Therefore, thermosetting materials have traditionally been considered to be unsuitable for ultrasonic waves.
▶ Material compatibility
▶ Other factors that affect the effect of ultrasonic welding
Materials with water absorption properties, such as polycarbonate, polysulfone, and nylon.
The proportion of the mixture should be noted after the plastic is added to the mixture.
Problematic release agent: Silicone grease, Teflon, internal lubricants, toner, recycled materials, fire retardant, etc.
2. Influence of ultrasonic welding equipment and fixture design on welding effect
▶ Main components of ultrasonic plastic welding machine: transducer, amplifier, welding head. The main materials of the ultrasonic amplifier and welding head are: titanium alloy or aluminum alloy.
▶ Select the welding machine of the appropriate frequency according to the size of the product.
▶ Ultrasonic welding head surface amplitude design.
Weld Head Surface Amplitude = Transducer Surface Amplitude x Amplifier Gain x Weld Head Gain
3.The structure of plastic parts
In order to obtain the perfect product appearance, strong and reliable solder joints, three main design directions must be followed:
First, 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 welding time) to complete the fusion.
Second, find a suitable method of fixing and alignment, such as the connection of plastic parts, steps or tongues.
Third, the welding head needs to directly contact and cover all the welding areas to meet the energy transmission required by the welding points.
4.Welding line design
The welding line is the part where the ultrasonic wave directly acts to melt, and the basic two design methods are: energy guiding, shear design.
5. Ultrasonic welding process control
In the ultrasonic welding operation, when the surface of the product is scratched, the joint is broken or cracked, the flash or burrs are generated, and the size after welding is not controlled within the tolerance, the equipment parameter control should be checked first and optimized by reasonable experiment. Execution parameters (pre-pressure, descent speed, delay time, welding time, reference media coverage (eg PE bag), mold surface)
(hardening or chrome plating), the number of machine stages is reduced or the upper mold expansion ratio is reduced, etc.) to obtain good quality. Ultrasonic waves propagate in plastic parts.
Plastic parts absorb or attenuate ultrasonic energy more or less, which has a certain influence on ultrasonic processing. Plastics generally have amorphous materials, and hard rubber and soft rubber are classified according to hardness. There is also a distinction between the modulus and, in a nutshell, the high-hardness, low-melting plastic ultrasonic processing performance is superior to the low-hardness, high-melting plastic. Therefore, this involves the near-far problem of ultrasonic machining distance.
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