Ultrasonic Welding Machine Main Components
These machines consist of several components with specific functions. Here are a few important parts you will find in all types of ultrasonic welding machines:
· Generator
The ultrasonic welding machine generator converts electrical energy with a resonant frequency into the required voltage and high frequency. In addition, it has a microprocessor responsible for driving the welding cycle and providing important welding communications through the user interface.
· Mechanical Press
The mechanical press holds the welding system and applies the force that holds the weld joint together. It has a pressure gauge and regulator that allows the operator to adjust the force applied to the system.
· Weld Stack
The welding stack consists of the transducer, booster, and welding horn that are mounted on the welder press at the center point of the booster. It is responsible for providing ultrasonic machine vibrations, the frequency of which must be close to that of the generator to obtain a quality weld joint.
· Sensor
The transducer or converter converts high-frequency electrical energy into mechanical vibrations. It consists of several piezoelectric ceramic disks placed between two titanium blocks. In addition, the electrodes are made of thin metal plates between the piezoelectric disks.
· Booster
The booster has two functions. First, it amplifies the vibrations generated by contracting and expanding and transfers them to the welding head. Second, it serves as a base for the weld pile on the welding machine.
· Welding Horn
The welding head is responsible for transferring the vibrations to the welded part. It is made of aluminum or titanium. However, aluminum is only suitable for small-volume applications because it wears. To reduce wear, most welding heads have hardened tips.
· Support Tool
The support tool serves to hold the lower part of the machine during the welding process. It is the base of the machine and is designed to match the contours of the workpiece.
How Ultrasonic Welding Works
Mechanism of Ultrasonic Welding
Ultrasonic welding is based on the process of heating and melting materials using vibrating sound waves. Here is a summary of how the process works:
Material Preparation: The plastic parts are arranged to form a lap joint and then placed on the welding pile of the machine.
Generation of High-Frequency Electricity: The generator of this machine converts electrical energy (50-60 Hz) into high frequencies (20 – 40 kHz).
Conversion to Ultrasonic Waves: The transducer converts the high-frequency electricity into ultrasonic waves. After that, the booster amplifies the vibrations.
Welding: The horn or sonotrode focuses ultrasonic vibrations on the aligned plastic or metal parts. The operator then applies pressure using a press. Once completed, the operator retracts the horn and removes the weld material.
Types of Ultrasonic Welding – Plastics and Metals
The welding process has limitations on the type and size of materials it is compatible with. The following are the common materials for this technology.
· Ultrasonic Plastic Welding
The ultrasonic welding process is one of the most common plastic welding techniques. It is suitable for welding thermoplastics such as polycarbonate, ABS, polyester, etc. However, it is best to be careful about properties such as the presence of moisture and hardness. Also, the process is not suitable for plastic polymers such as PVC and polyamide.
· Ultrasonic Metal Welding
The ultrasonic metal welding technique is compatible with a wide range of metals such as aluminum, copper, silver, brass, nickel, gold, and their alloys. However, the technique is only suitable for these metals that are thin and small in size.
· Material Selection Considerations
Choosing the right material is an important part of ultrasonic welding. However, there are some issues in choosing the right material for your end product.
Shape: The shape of the part should allow for overlapping because the technique is only suitable for overlapping.
Contains moisture: The material should not contain moisture as this will affect the quality of the welded part. Therefore, you should be careful about materials that can absorb moisture, such as acrylic.
Hardness: A suitable material must be soft, such as ABS. Due to the hardness of materials such as polypropylene and polycarbonate, this welding technique may not be suitable for these materials.
Thickness: Thick materials require more energy to vibrate and break the molecular bonds, and the machine may not be able to generate this energy. Therefore, this process is only suitable for thin parts (0.38mm – 3mm).
Similar materials: The ultrasonic welding process is suitable for welding two similar thermoplastic parts because they are chemically compatible. During the melting process, they can form a molecular bond.
Dissimilar materials: This welding process is also suitable for welding dissimilar materials. However, they must melt within 40 degrees 0F and have similar molecular structures. For example, ABS and acrylic are a good combination, while polyethylene and polypropylene are chemically incompatible.
In addition to the similarity of the materials, choosing the right material also depends on the presence of lubricants, fillers, pigments, etc. Therefore, getting advice from welding experts like us can be a game changer.
