Obtaining the optimum setup conditions for a given application using ultrasonic weld equipment usually requires a series of tests to determine the set of welding conditions that provide the best results. Although there is no solution for circumventing this testing procedure, a proper understanding of the principles and components of an ultrasonic assembly system will help to expedite the process of reaching the optimum setup conditions for a given application.
To begin our understanding of the optimizing process, it is necessary to understand the basic components that make up an ultrasonic welding system. The system usually consists of six basic components.
- The POWER SUPPLY changes 50/60 hz electrical energy into high frequency electrical energy and the power supply is rated in watts of available output power. Frequencies are available in 15, 20, 30 and 40KHz. Power output ranges from 150 watts to 4000 watts of power. It is important to remember that just because a unit is rated at a certain output power capacity does not mean that an application will require full power from the supply or that the power supply will have adequate power for a given application. The power supply provides power on a demand basis depending upon the amount of power required for the application and under a given set of conditions. The size and shape of the part, the material being welded, the joint design and welder setup variables that control the ultrasonic process can alter the amount of power drawn from a power supply.
- The CONVERTER is the motor of the ultrasonic system. This component produces a motion via a piezoelectric effect, which is to say that the converter expands and contracts when electrically excited by the power supply. At 20Khz, this expansion and contraction is approximately .001 of an inch at the face of the converter and the movement is in an axial motion. The converter is matched to the output frequency of the power supply.
- The BOOSTER is a machined piece of aluminum or titanium metal, which is tuned to resonate at the desired frequency and designed to increase or decrease the motion that is produced at the face of the converter. The following decreases/increases can be obtained depending upon the booster used. The booster is color coded to ease identification of the booster amplification. The booster is attached to the face of the converter via a mechanical stud.
|
Color |
Converter Amplitude |
Booster Gain |
= Output at Booster |
|
Purple |
.001 |
0.6:1 |
.0006 |
|
Green |
.001 |
1:1 |
.001 |
|
Gold |
.001 |
1.5:1 |
.0015 |
|
Silver |
.001 |
2.0:1 |
.002 |
|
Black |
.001 |
2.5:1 |
.0025 |
The booster is an important element in determining the output amplitude of the converter/booster/horn assembly. The correct booster and horn combination is very important because amplitude is a critical variable in achieving a successful application and in the amount of power delivered by the power supply.
- The HORN is a machined tool that resonates at the desired frequency. The horn is usually manufactured of titanium, aluminum or steel. The primary purpose of the horn is to uniformly transfer the ultrasonic energy to the work piece. The horn is usually made to match the shape of the part to most efficiently transfer this energy. Depending upon the size of the horn, there are various shapes of horn designs to increase the amplitude of the converter/booster/horn assembly. The horn is attached to the booster through the use of a mechanical stud.
- The ACTUATOR is the pneumatic delivery system of the ultrasonic power. Its components consist of:
a solenoid valve
a cylinder
a flow control valve
a pressure regulator
a gauge
a carriage to hold the converter/booster/horn assembly
a linear rail-bearing slide mechanism to deliver the
carriage with the horn to the part, and
a dynamic triggering mechanism to determine the amount
of pressure delivered to the part before the ultrasonic
energy is activated or turned on.
Actuator systems can be of a standard type or more intelligent units providing greater control and monitoring. The standard actuator and an intelligent actuator both deliver ultrasonic power to the work, but the intelligent actuator additionally provides the welding system with the ability to weld to distance, monitor distances during welding, digitally monitor the pressure gauge, electronically set the trigger force, monitor the trigger switch distance range and control and monitor the forces seen by the system during welding.
Pressure is a key variable in the delivery of ultrasonic power to the work. The dynamics and control of this variable are not well understood by most manufacturers that use the ultrasonic welding process.
- The POWER SUPPLY PROGRAMMER is the component that controls the sequencing, the duration, the delivery and monitoring of ultrasonic power applied to the work. On less sophisticated ultrasonic units, the duration of ultrasonic vibration is controlled primarily by time. Specifically, once ultrasonics is turned on or activated by a trigger switch, ultrasonic power continues to stay on until the duration of time is complete as established by the preset programmed time. With this type of programmer, there is limited control and monitoring of other system variables.
With the advent of technology, the capability to expand the modes of welding and the monitoring of the welding process has grown dramatically. The more sophisticated units allow the ultrasonic welding machines to weld by distance, weld by energy, weld by peak power, weld by a time/energy compensation mode and to monitor time, energy, force, power, down speed, amplitude, trigger distances, etc. It is the power supply programmer coupled with other system devices that provides all the modern day control and information about the process.
These six basic components provide the basis upon which we will continue our exploration of the dynamics of ultrasonic welding. It is important to understand the basic components before proceeding.
This dynamics of welding section will be expanded upon periodically with other pages in this site to provide you additional information that you can use to help you optimize your ultrasonic welding process. We invite you to check back with us frequently to make sure you don’t miss out on our next update. Thanks for your interest!
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