Hitachi UX Twin-Nozzle Technical Manual page 30

(3) Precautions related to welding current of welder
Signal (weak electric) ground and frame ground are connected because the ink drops of the IJ printer
are electrically charged.
Ink column
Nozzle
Signal ground
Charge theory
Therefore, when a large current (for example, the welding current of a welder) flows from the
outside through frame ground, the current is also diverted to signal ground and the PC boards may
be damaged and the earth cable may be fused. For this reason, whenever performing welding work
near the IJ printer, proceed as follows:
Method
Be sure to insulate the printhead and IJ printer frame to keep the welding current from flowing to
the control section of the printer, and to make a separate ground connection for the printer.
If this method is used, welding work becomes possible even while the IJ printer is operating.
IJ printer body frame
Primary power cable
E
Welding work cautions
●Fire is strictly forbidden around the IJ printer
The ink and makeup are both flammable. Welding sparks may cause ignition or a fire.
Take measures so that sparks do not enter the surrounding area whether or not the IJ
printer is operating, and ventilate sufficiently.
Just in case, ensure safety by installing a powder type fire extinguisher nearby.
Charge electrode The ink drops are electrically charged by impressing a
+++
voltage between the charging electrode and ink column
as shown at the left.
Therefore, the ink always becomes signal ground.
In addition, since the ink is always connected to frame
+++
ground by the clamp, etc. of the circulation path,
separating signal ground and frame ground is difficult.
WARNING
Print head unit
Stand (option)
Spaced by insulator
●Wiring precautions 4-2