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Limit Switches

Introduction Features
Principles Classifications
Engineering Data Further Information
Explanation of Terms Troubleshooting

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ProblemProbable causeRemedy
Mechanical
failure
1) The actuator
does not operate.
2) The actuator
does not return.
3) The actuator
has been
deformed.
4) The actuator
is worn.
5) The actuator
has been
damaged.
The shape of the dog or cam is
incorrect.
・ Change the design of the dog or cam and
smooth the contacting surface of the cam.
・ Scrutinize the suitability of the actuator.
Make sure that the actuator does not bounce.
The contacting surface of the
dog or cam is rough.
The actuator in use is not suitable.
The operating direction of the
actuator is not correct.
The operation speed is excessively
high.
・ Attach a decelerating device or change the
mounting position of the Switch.
Excessive stroke.・ Change the stroke.
The rubber or grease hardened due
to low temperature.
・ Use a cold-resistive switch.
The accumulation of sludge, dust,
or cuttings.
・ Change to a drip-proof switch or one that
provides a high degree of protection.
・ Use a protection cover and change the
solvent and materials.
Dissolution, expansion, or swelling
damage to the rubber parts of the
driving mechanism.
There is a large
deviation in
operating
position (with
malfunctioning
involved).
Damage to and wear and tear of the
internal movable spring.
・ Regularly inspect the Switch.
・ Use a better quality switch.
・ Tighten the mounting screws securely.
Use a mounting board.
Wear and tear of the internal
mechanism.
The loosening of the mounting
screws causing the position to be
unstable.
The terminal
part wobbles.
(The mold part
has been
deformed.)
Overheating due to a long soldering
time.
・ Solder the Switch quickly.
・ Change the lead wire according to the carry
current and ratings.
The Switch has been connected to
and pulled by thick lead wires with
excessive force.
High temperature or thermal shock
resulted.
・ Use a temperature-resistive switch or
change mounting positions.
Failures
related to
chemical or
physical
characteristics
Contact
chattering
Vibration or shock is beyond the
rated value.
・ Attach an anti-vibration mechanism.
・ Attach a rubber circuit to the solenoid.
・ Increase the operating speed (with an
accelerating mechanism).
Shock has been generated from a
device other than the Switch.
Too-slow operating speed.
Oil or water
penetration
The sealing part has not been
tightened sufficiently.
・ Use a drip-proof or waterproof switch.
・ Use the correct connector and cable.
(Use a sealed connector for sealed switches.)
The wrong connector has been
selected and does not conform
to the cable.
The wrong switch has been selected.
The terminal part is not molded.
The Switch has been burnt or
carbonated due to the
penetration of dust or oil.
Deterioration
of the rubber
part
The expansion and dissolution of
the rubber caused by solvent or
lubricating oil.
・ Use an oil-resistant rubber or fluororesin
bellows.
・ Use a weather-resistant rubber or protective
cover.
・ Use a switch with a metal bellows protective
cover.
Cracks due to direct sunlight or
ozone.
Damage to the rubber caused by
scattered or heated cuttings.
Corrosion
(rusting or
cracks)
The oxidation of metal parts
resulted due to corrosive solvent
or lubricating oil.
・ Change the cutting oil or mounting position.
・ Use a crack-resistant material.
The Switch has been operated in
a corrosive environment, near the
sea, or on board a ship.
The electrical deterioration of
metal parts of the Switch resulted
due to the ionization of cooling
water or lubricating oil.
The cracking of alloyed copper due
to rapid changes in temperature.
Failures related
to electric
characteristics
No actuation.
No current
breakage.
Contact welding
Inductive interference in the DC
circuit.
・ Add an erasing circuit.
Brown powder generated due to
switching operations
・ Use a switch with a special alloy contact or
use a sealed switch.
A short-circuit or contact weld
due to contact migration.
・ Reduce the switching frequency or use a
switch with a large switching capacity.
Contact weld due to an incorrectly
connected power source.
・ Change the circuit design.
Foreign materials or oil penetrated
into the contact area.
・ Use a protective box.