Touch Sensor (Seam Search) - Kemppi A3 MIG Operating Manual

4.8 Touch sensor (seam search)

The touch sensor is a specific functional system used in
automated welding for finding workpiece's accurate lo-
cation and position. The touch sensor hardware and I/O
are in the welding power source. A welding robot finds
the edges of the workpiece by touching them either with
a welding wire or a gas nozzle. Touches are detected by
the touch sensor and the information is passed on to the
robot controller.
The touch sensor generates a sensing voltage separately
from the welding power source. Touch is detected when
there is a short-circuit between the workpiece and the
sensing tool resulting in a voltage drop. The negative
pole of touch sensor's voltage source is connected to a
welding minus. The positive pole of the sensor is connect-
ed either to a welding plus or a gas nozzle. The target for
the positive pole can be changed by a user. A relay in the
touch sensor device enables the configuration by a DIP
switch.
The touch sensor system consists of hardware and soft-
ware. The hardware consists of a touch sensor device and
wiring in the wire feeder's control cable for the gas nozzle
use (see Figure 4.4, "Touch sensing system"). The software
enables configuration and control. The touch sensor is
configured by using DIP switches, and it is controlled by
the welding robot via the digital robot interface.
Figure 4.3 Touch sensor in the power source
1. Touch sensor device inside the welding power source
2. Wire feeder control cable connector (wiring for the gas
nozzle)
3. Fieldbus / Digital robot interface
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© Kemppi Oy 2018
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Figure 4.4 Touch sensing system
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A3 MIG Welder
Fieldbus
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Configuration (DIP switches)
Welding plus (welding wire touch sensing)
Wire feeder control cable (gas nozzle touch
sensing)
Fieldbus / Digital robot interface
Peripheral connector
Touch tool (welding wire or gas nozzle)
Touch detection
Welding minus (touch sensor ground)
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