JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe - 94

US-welding
Full parameter control
In this process, just controlling the ultrasonic frequency
and amplitude parameters is not enough. It is important to
define and control the viscoelastic properties of the materials, the contact features (geometry), the sonotrode and anvil
materials (thermal translation factor), the stresses acting on
the energy exchange zone, and the velocity that defines the
process time.

However, we can say that the technology has already been
used on aviation parts, e.g. spot welding of small, high-performance thermoplastic-matrix (e.g. PA, PEEK, PEI) parts,
processing non-developable shapes as part of a continuous
process, or combining metal inserts and welded fabrics to
form resistive skins.

The maximum temperature is obtained near the interface
between the two parts (Figure 6).

Fig. 6: Temperature at the nodes

To achieve satisfactory process control, specific control algorithms were developed to take all significant parameters into
account. One or more floating parameters enabling control
were selected based on the requirements of the Product/Machine couple.
The diagram in
Figure 7 shows the
influence of the
velocity/contact
time parameters on
the temperature in a
continuous process
(the other parameters being fixed).
It can be observed
that the temperature
reached depends on
Fig. 5: The energy dissipated at a given velocity
velocity in a nonunder ultrasonic pressure p=p0sin(2πft)
linear way. The final
calories that require a higher energy level provide finer system
control. It can also be observed that the temperature drops
rapidly after the pass under the ultrasonic effector. Using
insulation or cooling to control the temperature drop makes it
possible to control the crystallinity of the welded polymer.

Applications
In addition to static welding of small parts, continuous processes that combine metal inserts and welded fabrics to form
resistive skins are already used at the industrial scale. The
welding of stiffer elements for which the means of implementation are heavier but meet the same criteria still needs to be
industrialized, however.
For the moment, nondisclosure issues with our industrial
partners prevent the mention of any specific application, due
to the high added value of the technology.

94 jec composites magazine / No87 March 2014

Fig. 8: Robotized ultrasonic welding

Figure 8 shows an example of a robotized ultrasonic welding
effector. Both effector and tool are dedicated to the application. The robot moves the effector along the welding path. The
control algorithms dialogue with the robot, the ultrasound
generator and the different sensors on the effector. For high
energy consuming applications, the effector could be a multitechnology one. Layup and welding of a reinforcement or tape
on a 3D form is also possible.

Conclusions
It is already possible to use ultrasound technology to integrate
the welding of thermoplastic parts and multi-material assembly into the industrialization process for existing parts.
However, there are greater prospects upstream, during the
product-material-process development phases.
Thanks to advantages like shorter cycle times with fewer tools
required, and the continuous control, it is possible to produce
large and/or complex-geometry structural parts in a single
shot, for larger-series markets in the aerospace and automotive sectors.
The Sonimat team has twenty years of experience in thermoplastic assembly and is positioned for multiple technologies.
Thanks to their well-known expertise in terms of understanding the phenomena generated and controlling individual or
combined welding processes, the team members are able to
collaborate on highly demanding development projects. n
More information:
www.europetechnologies.com
Contact:
c.schimel@europetechnologies.com

http://www.europetechnologies.com

JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #87 - March 2014 Special JEC Europe