Illinois Tool Works IJ300, Руководство по эксплуатации

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Controller
Appendix J: Electrostatic Discharge (ESD)
5760-121 Operations Manual Rev B Page 113 of 115
Appendix J: Electrostatic Discharge (ESD)
What is ESD?
Electrostatic Discharge (ESD) is a triboelectric charge generated by separating or rubbing
together two non-conductive materials.
What causes ESD?
Friction can cause ESD. Friction can be generated by walking across a floor, removing
tape from a tape dispenser, pulling a work order from a plastic work order holder, rolling the
wheels of a push-cart across the floor, sitting on a foam cushion such as a stool or blowing
air across a nonconductive surface.
ESD at the print station can be caused by the product rubbing against ungrounded guide
rails, conveyor belt static voltage build-up, or a residual static charge on the product from
earlier processing.
Generally, ESD problems are more prevalent in the winter months. Heated air has a much
lower relative humidity than the cold air had prior to heating. In many instances ESD prob-
lems appear in the fall when the outside temperature drops, and go away in the spring
when the outside temperature begins to rise.
What are the effects of ESD?
Unexplainable system resets, controller lockups, and multiple prints on the product can be
signs of static discharge to the system. When static electricity is discharged to an electronic
circuit (components or printed circuit boards), permanent damage may also occur. This
damage may be in the form of reduced functionality, reduced life, or complete non-function-
ality.
The static charge does not have to be noticeable to the human touch in order to cause
problems in an electronic system. A human being does not start to feel the effects of static
electricity until the voltage reaches or exceeds 4000 volts. Voltage as small as 100 volts
can cause problems with some sensitive electronic components.
What prevents ESD?
Prevention begins with training and knowledge. The use of wrist straps, heel straps, work-
bench mats, floor mats, and monitoring systems for electronic devices will drastically
reduce the ill effects of ESD when handling circuit boards. ESD wrist straps should be used
when handling electronic components or printed circuit boards.
If static discharge is suspected of causing controller problems at the print station, check the
grounding of the conveyor and print station components. Nonconductive or ungrounded
guide rails are the most common cause of static discharge. Ionized air blowers and static
dissipating material have proven effective in eliminating many static problems.
Source 70-90% Relative
Humidity Volts 10-20% Relative
Humidity Volts
Walking across a carpet 1,500 35,000
Working at a bench 100 12,000
Sitting on a foam cushion 600 20,000
Removing plastic bag from bench 12,000 20,000
Removing work-order from plastic pouch 600 7,000