DCM00002 REV. 16 19
The power required to initiate and maintain vibration (motion) during the weld cycle can
be defined as:
*Force = (Surface Area of the Cylinder) X (Air Pressure) X (Mechanical Advantage)
Energy is calculated as;
Thus the complete ‘Weld To Energy’ process would be defined as:
E = (F x A x f) x T
A well designed ultrasonic metal welding system will compensate for normal variations in
the surface conditions of the metals by delivering the specified energy value. This is
achieved by allowing Time (T) to adjust to suit the condition of the materials and deliver
the desired energy.
2.5.4 Welding To Energy - Why?
Most metal welding applications are produced by ‘Welding To Energy’ in order to
compensate for the various surface oxides and contaminants associated with the metals
being joined. In a few applications ‘Welding To Time’ or ‘Welding To Height’ will yield better
results. Since the majority of all metal welds are produced using energy as the controlling
factor we will confine our discussion to that condition.
Welding to energy is necessary because of the non-metallic oxides that form on the
metal’s surface as well as other contaminates such as grease and dirt. To produce quality
welds reliably it is necessary that the surfaces to be joined are clean. The high frequency
scrubbing action, combined with pressure, cleans the weld interface at the beginning of
the weld process.
The following graph (Figure 2.4 Weld Power Graph for clean components, dirty
components, and when part is missing) illustrates a weld produced. The weld ‘power
graph’ is sometimes referred to as weld ‘footprint’. It can be used to visualize the weld
cycle and assists in parameter optimization. Graphs from consecutive welds will vary
slightly as the system dynamically adjusts time to accommodate varying surface
conditions. The weld power data is gathered by sampling the power used in 5 millisecond
intervals.
Table 2.2 Calculating Power
P = F x A x f
Where:
• P = Power (watts)
• F = Force* (N)
• A = Amplitude (microns)
• f = Frequency (Hertz)
Table 2.3 Calculating Energy
E = P x T
Where:
• E = Energy (joules)
• P = Power (watts)
• T = Time (seconds)
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