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Ultrasonic Welding Equipment |
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Ultrasonic Welding Equipment -
Ultrasonic welding equipment consists of
1. A frequency converter.
2. A transducer-coupling system.
3. An anvil.
4. A force application device.
5. A timer.
6. Appropriate electrical, electronic and hydraulic or pneumatic controls.
1. A frequency converter provides high-frequency electrical power at the design frequency of the welding system. Ultrasonic welding equipment may be driven by electron tube frequency converters, motor-alternators, or silicon-controlled-rectifier converters.
2. A transducer coupling system consists of a transducer that converts the electrical power to elastic vibratory power and a coupling system including the sonotrode tip which conducts vibratory power to the weld zone.
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Both, magnetostrictive transducers consisting of laminated A nickel stacks (which are less sensitive to overloading and heating than the various electrostrictive ceramic materials) and electrostrictive transducers of material such as lead zirconate titanate are used in welding systems.
Magnetostrictive materials change length under the influence of varying magnetic flux density. Such transducers are rugged and serviceable for continuous duty operation but they have a low practical overall efficiency generally within the range of 20 to 40% against efficiency of lead zirconate titanate, which is an electrostrictive ceramic material and is capable of changing dimensions when subjected to an electrical field parallel to the plane of polarization. Either type of transducer is cooled to prevent overheating and maintain its characteristics.
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For high reliability, various joints in the transducer coupling system must have high integrity and fatigue resistance. A survey of promising materials for sonotrode tips indicates the superiority of nickel based super alloys.
Sonotrode tip radius, while not highly critical as to specific values, is an important general consideration, for it affects the weld area and thus the machine setting of clamping force, power and pulse time or rolling rate. It is usual to have a slightly radiused face on the sonotrode tip. The radius is kept between 50 and 100 times the thickness of the sheet adjacent to the tip.
3. An anvil serves as a backing for the workpieces and provides the necessary reaction to clamping force. An anvil must not permit compliance of the workpiece with the applied vibration. To prevent energy loss the anvil assembly should be structurally isolated from the welder frame.
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4. A force application device applies static load normal to the plane of weld surface. It is
(i) Spring actuated for very small machines,
(ii) Pneumatically actuated in medium size machines, and
(iii) Hydraulically actuated with larger units.
5. A timer controls the weld interval in spot type, ring and line welding or a rotating and translating mechanism for continuous seam welding.
Weld interval is automatically controlled by logic circuitry.
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