July 15, 2026 · Robot Cell Safety
Most robot safety attention goes to keeping people out of a running cell: fences, interlocked gates, light curtains, scanners. But there is one task that deliberately puts a trained person inside the safeguarded space with the servos live, and it is one of the most dangerous things anyone does around a robot. That task is teaching. When a technician jogs the arm to program points or verifies a new path, the robot cannot be at a zero-energy state, because the whole point is to move it. So the standards do not rely on isolation here. They rely on a specific, layered set of controls built around reduced speed and a held enabling device. Understanding those controls is the difference between routine programming and a struck-by injury.
This guide covers how teach mode is supposed to work, what the T1 and T2 modes mean, why 250 mm/s is the number, how the enabling device is designed to fail safe, what the 2025 standards changed, and the line every plant has to keep clear between teaching and lockout.
For servicing and maintenance, the rule is simple: isolate the energy, verify zero state, and work. That is lockout/tagout, and it is the right regime whenever the task does not require the robot to be powered. Teaching is the exception. You cannot teach a point or verify a motion path on a dead robot. The task itself requires controlled motion, which requires power. So the standards accept that a person will be inside the cell with a live robot and pivot from isolation to a set of engineered constraints that make that live-power work as safe as it can be. The key word is controlled. Teach mode is not "the robot is on and we are being careful." It is a defined mode with hard limits enforced by the safety controller.
ISO 10218-1, the international robot safety standard that ANSI/RIA R15.06 adopts in the US, defines three operating modes. Getting the vocabulary right matters, because the plant floor often blurs them.
| Mode | What it is | Speed and access |
|---|---|---|
| Automatic | Normal production cycle | Full speed, no one inside the safeguarded space |
| T1, manual reduced speed | Jogging, teaching, program verification | Tool-center-point speed limited to 250 mm/s; person may be inside with an enabling device |
| T2, manual high speed | Program verification at production speed | Above 250 mm/s; highest risk, tightly restricted |
Automatic is production, and safeguarding keeps people out. T1 is the workhorse teaching mode and the one most technicians live in. T2 exists because sometimes a program has to be verified at real production speed, but it is the most hazardous manual mode by far, and the standards treat it accordingly. The mode is chosen at a selector on the pendant or controller, and which mode is active governs everything about what the robot is allowed to do.
The 250 mm/s tool-center-point limit in T1 is not arbitrary. It is the speed judged slow enough that a person working next to the arm has a realistic chance to perceive unexpected motion, react, and either move clear or release the enabling device before being struck or pinned. At roughly ten inches per second, an unexpected move is still fast enough to hurt, but slow enough to give the human in the loop a fighting chance. That is the entire logic of reduced speed: it does not prevent contact by itself, it buys the reaction time that the other layers, the enabling device and the trained operator, need to work. It is a headline requirement of both ISO 10218-1 and ANSI/RIA R15.06, and on a compliant cell it is enforced by the safety-rated controller, not merely requested in software.
The second pillar of teach-mode safety is the enabling device, the switch a technician must hold for the robot to move in manual mode. It is deliberately a three-position switch, and the design is elegant.
The genius is that both instinctive human reactions to a fright, throwing your hand open or clamping it shut, drive the switch to a stop state. Only the deliberate, moderate hold in the middle allows motion. A technician startled by an unexpected move does not have to think about hitting a stop; their reflex already is the stop. Combined with the 250 mm/s cap, the enabling device is what makes standing inside a live cell a controlled risk rather than a gamble.
The robot safety standards were revised in 2025, and several changes tighten manual operation specifically. Plants running to the older text should understand what moved. The ISO 10218-1:2025 revision requires the mode selector to be a lockable device, such as a key-operated switch, with each position clearly identifiable and exclusively enabling a single mode, so a robot cannot sit in an ambiguous or easily-flipped state. Manual high speed T2 is now restricted to outside the safeguarded space, meaning that inside the safeguarded zone only T1 reduced speed is permitted. And for the higher robot class, the reduced speed in T1 must be safely monitored, not just commanded, so a fault cannot silently let the arm exceed 250 mm/s while someone is inside. These are meaningful upgrades for any West Michigan plant updating cells or specifying new automation.
Here is the mistake we see most on audits, and it is a serious one: using teach mode as a stand-in for lockout. A technician needs to clear a jam or adjust tooling, and rather than isolate the cell they flip to T1 and reach in. Teach mode reduces risk while the robot is powered, but it does not isolate energy, and it does nothing about the pneumatic clamps, the weld power, or the stored energy in a loaded axis. If a task does not genuinely require live, controlled robot motion, it is servicing, and servicing belongs under lockout/tagout at a zero-energy state, per OSHA 1910.147 and MIOSHA Part 85. Teaching is for tasks that must have the robot live. Everything else gets locked out. Keeping that line sharp is one of the most important things a robotics safety program does, and it ties directly to how the broader robot cell LOTO standards align and how the cell's safeguarding devices protect people during production.
On robotics safety assessments across West Michigan we see a recurring set of teach-mode gaps. Enabling devices that have been defeated with tape or a zip tie so a technician does not have to hold them, which throws away the entire fail-safe design. Mode selectors that are not lockable, so anyone can flip to a hazardous mode. Teaching performed by untrained operators who do not understand the pendant or the cell. Reduced speed that is commanded in the program but not safely monitored, so a fault can exceed it undetected. And the big one, teach mode used routinely for work that should be under lockout. Each of these turns a well-designed safety regime back into the hazard it was built to control, and each is exactly what a cell risk assessment is meant to catch.
We assess how your cells handle manual operation: mode-selector and enabling-device integrity, safely-monitored reduced speed, the T1 and T2 boundaries under ISO 10218-1:2025 and ANSI/RIA R15.06, trained-operator requirements, and the critical line between teaching and lockout under OSHA 1910.147 and MIOSHA Part 85. Then we write the procedures and controls your West Michigan plant needs.
Request Gap AssessmentTeach mode is the manual mode used to jog, program, and verify a robot with the automatic cycle suspended. Under ISO 10218-1 it is the manual reduced speed mode, commonly called T1. It exists because some tasks, teaching points and checking programs, cannot be done with the robot fully de-energized, so the standard controls the risk instead: the operator works close to a powered robot whose tool-center-point speed is limited to 250 mm/s and whose motion requires a held enabling device.
T1 is manual reduced speed mode: jogging, teaching, and program verification with tool-center-point speed limited to 250 mm/s or less. T2 is manual high speed mode, which allows motion above 250 mm/s for program verification at production speed. T2 is far more hazardous, and under ISO 10218-1:2025 it is restricted to outside the safeguarded space; inside the safeguarded zone only T1 reduced speed is permitted.
Because 250 mm/s is slow enough that a person working inside the cell has a realistic chance to see unexpected motion and move clear, and to release the enabling device to stop the robot, before being struck or trapped. The limit, set in ISO 10218-1 and ANSI/RIA R15.06, applies to the tool-center-point speed during manual reduced speed operation. It is a deliberate risk-reduction number, not an arbitrary setting.
It is the enabling switch on the teach pendant that must be held in its center position for the robot to move in manual mode. Fully released (position 1) stops the robot. Fully squeezed in a panic grip (position 3) also stops it. Only the light center hold (position 2) permits motion. It is designed so that both letting go and clenching, the two instinctive reactions to a scare, cut motion, which is why it is central to safe teaching.
No, and confusing the two is dangerous. Teach mode is a safeguarding regime for tasks that require the robot powered, like teaching points. Lockout/tagout under OSHA 1910.147 is for servicing and maintenance, where the robot must be at a zero-energy state. If a task does not require live power, it should be done under LOTO, not in teach mode. Teach mode reduces risk while power is on; it does not isolate energy.
The 2025 revision clarifies and tightens manual operation. The mode selector must be a lockable device, such as a key switch, where each position is clearly identifiable and exclusively enables one mode. Manual high speed (T2) is restricted to outside the safeguarded space, so only T1 reduced speed is allowed inside it. And the reduced speed in T1 must be safely monitored for the higher robot class, rather than merely commanded.
Only trained, authorized personnel who understand the specific robot, its pendant, the enabling device, and the cell. Teaching puts a person inside the safeguarded space with a powered robot, which is one of the highest-risk tasks in the plant, so training and written procedures are not optional. Many serious robot incidents happen during teaching and maintenance, not production, which is exactly why the standards govern this mode so tightly.
Related reading: Robot Cell LOTO Standards Alignment, Light Curtains and Laser Scanners for Robot Cells, Fenceless Robot Cell Risk Assessment.