FANUC Safety Standards & Compliance in Robotics 5 — Questions and Answers
Question 1: Under NFPA 79 (Electrical Standard for Industrial Machinery), what color must the emergency stop actuator (push button) be on a FANUC robot control panel?
- Yellow with red background
- Red with yellow background (Correct answer)
- Solid red
- Solid yellow
Correct answer: Red with yellow background
NFPA 79 requires the emergency stop actuator to be red with a yellow background to provide maximum visual contrast and immediate identification.
Question 2: Which safeguarding method defined in ISO 10218-2 uses robot force and power limiting to make physical contact with a human inherently safe?
- Speed and separation monitoring (SSM)
- Hand guiding
- Power and force limiting (PFL) (Correct answer)
- Safety-rated monitored stop
Correct answer: Power and force limiting (PFL)
Power and Force Limiting (PFL) is the collaborative method where the robot's hardware or control system inherently limits contact forces to safe levels, allowing direct human contact.
Question 3: A FANUC robot's emergency stop circuit must be designed to which safety circuit category per IEC 60204-1 to achieve a safety-rated stop?
- Category 0 — uncontrolled removal of power
- Category 3 — redundant, self-monitoring circuit
- Category 4 — redundant, self-monitoring with high diagnostic coverage (Correct answer)
- Category 1 — controlled stop then power removal
Correct answer: Category 4 — redundant, self-monitoring with high diagnostic coverage
E-stop circuits on industrial robots typically require IEC 60204-1 Category 4 safety relay architecture with dual-channel redundancy and high diagnostic coverage to achieve PLe/SIL 3.
Question 4: When a FANUC robot is operated in 'Automatic mode' with the safeguarding in place, what additional device is required before the robot can be restarted after a safety stop?
- A second emergency stop must be pressed
- A deliberate manual reset of the safety circuit is required (Correct answer)
- The teach pendant must be connected
- The robot must be re-homed to the zero position
Correct answer: A deliberate manual reset of the safety circuit is required
After a safety stop in automatic mode, ANSI/RIA R15.06 and ISO 10218 require a deliberate manual reset action to prevent unintended automatic restart.
Question 5: In ISO 13849-1, what does 'CCF' (Common Cause Failure) refer to in the context of a FANUC dual-channel safety circuit?
- Failures in both channels caused by the same root cause, defeating the redundancy (Correct answer)
- Failures that occur simultaneously but for different reasons
- Cascade failures propagating from one channel to the other through software
- A single-point failure in the output stage only
Correct answer: Failures in both channels caused by the same root cause, defeating the redundancy
CCF is when a single cause (e.g., overvoltage, temperature, EMI) simultaneously fails both channels of a redundant safety system, eliminating the protection that redundancy is designed to provide.
Question 6: According to ANSI/RIA R15.06-2012, which personnel qualification is required before someone can perform maintenance inside a FANUC robot's safeguarded space?
- Any employee with general OSHA safety training
- Only FANUC-certified technicians
- Qualified person trained in the specific robot system's hazards and lockout/tagout procedures (Correct answer)
- Personnel with at least 5 years of manufacturing experience
Correct answer: Qualified person trained in the specific robot system's hazards and lockout/tagout procedures
ANSI/RIA R15.06 requires that personnel entering the safeguarded space be 'qualified persons' — specifically trained and authorized for the robot system's hazards and applicable energy control (LOTO) procedures.
Question 7: What is the key functional difference between a 'safety-rated monitored stop' and a 'protective stop' in ISO/TS 15066 collaborative robot applications?
- Safety-rated monitored stop cuts power; protective stop maintains power and position (Correct answer)
- Protective stop requires the human to leave before restart; safety-rated monitored stop allows restart without human departure
- Safety-rated monitored stop is for T1 mode only; protective stop is for automatic mode
- There is no difference — the terms are interchangeable
Correct answer: Safety-rated monitored stop cuts power; protective stop maintains power and position
A safety-rated monitored stop (SRMS) removes drive power while monitoring that the robot has not moved; a protective stop (Category 2) keeps power applied and maintains position hold for quick restart.
FANUC Safety Standards & Compliance in Robotics 5
Under NFPA 79 (Electrical Standard for Industrial Machinery), what color must the emergency stop actuator (push button) be on a FANUC robot control panel?