Application of PTFE membranes to electronic casings
For good air exchange
(Erlangen) To
weld a thin PTFE membrane to PA6.6 so that it is leak-proof and without damage
is one of the more demanding tasks of ultrasonics technology. Especially since
conventional methods often cause the thin bars in casings to break. With
TELSONIC's SONIQTWIST® ultrasonic torsional welding process a machine and plant
manufacturer succeeds in producing reliable weld connections. The process
ensures that electronic casings in the engine compartment of motor vehicles
have adequate humidity and hot air exchange.
"The
exchange of air and the dispersal of moisture is extremely important for the
proper function of electronic components in the engine compartment of motor
vehicles", explains Wolfgang Ott, TELSONIC's head of the department for
plastic welding. This is achieved by an equalisation opening in the cover of
the PA6.6 casing. Below this opening which, for greater stability, is crossed
by two thin bars, a water- and pressure-tight PTFE membrane is welded. Any
excess pressure generated inside the casing due to the heat in the engine
compartment can escape through this membrane. It also allows moisture from
condensate to disperse from the inside to the outside.
Producing
reliable welds with critical materials
It was not
possible to weld this very delicate thin membrane using the longitudinal
ultrasonics process because the materials did not bond properly. Furthermore,
owing to the directional vibrations the thin bars were often damaged. The
solution was found in the SONIQTWIST® torsional ultrasonic welding process offered
by TELSONIC AG. The pioneer of ultrasonics succeeded with a standard TSF750
welding machine which was adapted to the production plant. This welding process
with the unique torsional technology is reliable and repeats welds accurately
irrespective of the different materials and combinations. The first-tier
supplier produces about 4000 parts per day.
In the
process, the welding machines weld different PTFE material combinations to a
range of different polyamide materials of the casing covers which, depending on
the type, may contain more or less glass particles. The converters convert the
1000 Watt output produced by the latest generation generator into a torsional
movement and apply it evenly and without disturbance to the welding zone. The
weld connection is perfect and the bars remain intact.
Sonotrode also
performs handling operations
In addition,
the welding machine performs handling operations as it collects and assembles
parts. The sonotrode is fitted with a vacuum system with the help of which it
collects the pre-cut membrane and places it at exactly the position where it is
welded. No separate handling unit is required. The vacuum system can also be
used to cut the membrane directly out of the carrier board or backing tape and
place it in position where it is then welded. Maximum automation for a good air
exchange.