Cobot Safety Standards Explained
Cobot safety standards, defined by ISO/TS 15066, dictate the exact speed, force, and power limits collaborative robots can exert alongside human operators.
Table of Contents
Cobot safety standards, defined by ISO/TS 15066, dictate the exact speed, force, and power limits collaborative robots can exert alongside human operators. Buying a collaborative robot does not automatically make your production line safe. A robot arm is merely a single component in a broader automation cell.
A collaborative robot is only considered safe for fenceless operation after a full application risk assessment proves the entire cell-including end-effectors and workpieces-meets ISO/TS 15066 force limits. If you attach a sharp metal tool to a certified collaborative arm, that system is no longer safe for human contact. The safety rating applies to the application, not just the hardware out of the box.
We design and install fenceless automation cells from our base in Odense, Denmark, and the most common misconception we correct is the idea that physical cages are simply obsolete. Cages are only obsolete when you can mathematically prove that an accidental impact between the robot and an operator will not cause injury.
The Regulatory Framework for Fenceless Automation
Industrial automation relies on a strict hierarchy of safety directives. When we integrate systems using brands like Universal Robots, we follow two primary documents that govern collaborative operation globally.
The first is ISO 10218 (Parts 1 and 2). This standard covers the safety requirements for industrial robots and robot systems. It established the baseline for what makes a robot legally safe to operate in a factory setting.
The second, and more specific document, is ISO/TS 15066. Published specifically to address human-robot collaboration, this technical specification provides the actual numbers. It maps out pain thresholds for 29 specific body areas and defines exactly how much force a machine can apply to a human worker before the system must trigger an emergency stop.
Understanding these standards is your baseline for passing local workplace safety inspections and preventing costly production stops.
The Four Collaborative Operating Modes
ISO standards classify human-robot interaction into four specific modes. You do not need to use all of them, but your application must fit into at least one of these categories to operate legally without a safety cage.
| Collaborative Mode | How It Works | Typical Application Scenario |
|---|---|---|
| Safety-Rated Monitored Stop | The robot stops moving entirely whenever a human enters the collaborative workspace. It resumes automatically once the worker leaves. | Manual loading and unloading stations where operators frequently swap out empty pallets. |
| Hand Guiding | The operator physically moves the robot arm using a specialized guiding device. The robot only moves when the human is actively driving it. | Teaching the robot a new path or positioning heavy objects like car doors precisely. |
| Speed and Separation Monitoring | The system uses scanners or cameras to track human movement. As the human gets closer, the robot slows down. If the human gets too close, it stops. | High-speed packing cells where occasional operator intervention is needed without halting the whole line. |
| Power and Force Limiting (PFL) | The robot and human work in the exact same space simultaneously. The robot relies on built-in sensors to stop safely upon physical contact. | Assembly tasks where human workers and robots manipulate the same workpiece together. |
Many of the Dobot robots we deploy operate in a combination of Speed and Separation Monitoring and Power and Force Limiting. This hybrid approach gives you the high throughput of a traditional industrial robot when humans are far away, and the safe contact limits of a cobot when operators step in to clear a jam.
Calculating Force Limits for Power and Force Limiting
Power and Force Limiting (PFL) is what most people picture when they think of a collaborative robot. The robot hits your arm, detects the spike in resistance, and stops before causing a bruise.
Pain onset thresholds dictate your maximum cobot speed; the ISO standard specifies that a quasi-static impact to a human hand cannot exceed 140 Newtons of force.
To meet this standard, you must understand the difference between two types of impact:
- Transient contact: The operator's body part can freely move away from the impact. Think of a robot bumping your shoulder while you walk past. The force limits for transient contact are higher because the energy dissipates as you move.
- Quasi-static contact: The operator's body part gets trapped between the robot and a fixed surface, like a workbench. The force limits here are much lower because the human absorbs the entire impact.
Across the palletizing and box-erecting cells we installed in Q1 2024, we found that limiting standard operating speeds to 1,000 millimeters per second generally keeps incidental contact forces well below ISO limits for blunt end-effectors. However, speed is just one variable. The payload mass and the shape of the part matter equally. A blunt suction gripper pushing your arm is a nuisance; a sharp metal bracket moving at the exact same speed is a puncture hazard.
When installing smaller units like the MG400 for lightweight, desktop-level sorting, the moving mass is low enough that keeping forces under the 140 Newton threshold is straightforward. Heavy-duty palletizers require much tighter speed controls when operating in PFL mode.
Conducting a Valid Risk Assessment in Five Steps
You cannot deploy a cobot legally without a documented risk assessment. This document proves to regulators that you have identified every way the machine could hurt someone and taken steps to prevent it.
We follow a strict, sequential process when auditing a new cell design.
- Define the limits of the machinery. Determine exactly what the robot will do, what materials it will handle, and the physical boundaries of its reach. Include the maximum payload and the specific geometry of the end-effector.
- Identify tasks and hazards. Walk through every phase of the robot's lifecycle. How will the operator clear a jam? How will maintenance clean the sensors? List every potential hazard, from crushing fingers between boxes to electrical faults.
- Estimate and evaluate the risk. For each hazard, assess the severity of the potential injury and the likelihood of it happening. A high-speed pinch point near the operator's main working area carries a much higher risk score than a blunt impact zone near the ceiling.
- Implement risk reduction measures. Modify the cell to eliminate the highest risks. This might mean padding the end-effector, restricting the robot's movement angles so it cannot reach operator eye level, or adding safety scanners.
- Document and validate. Test the physical setup. Use specialized force-measuring gauges to record the actual impact forces at various speeds. Document these numbers to prove they fall below the ISO/TS 15066 limits.
A risk assessment is a living document. If you change the product you are handling, you change the weight and shape of the payload. That requires an updated assessment.
Balancing Operator Safety with Throughput Goals
The most common objection we hear from production managers is that safety standards slow production down too much. If a cobot has to run at 20% of its maximum speed just to stay under force limits, the expected one-to-four-year ROI timeline extends drastically.
You solve this by layering your safety systems.
You don't have to restrict the robot to collaborative speeds all day. We frequently deploy area safety scanners linked directly to the robot's controller. When running complex routing logic like our SmartPack-Nordic 2 software for mix-palletizing, the robot runs at high industrial speeds as long as the work zone is empty.
If a forklift driver steps within three meters of the cell, the scanner detects them and drops the robot's speed to a collaborative level. If the driver steps within one meter, the robot triggers a Category 0 stop, cutting power to the motors entirely.
This layout means you get the cycle times of an industrial cage setup with the floor-space savings of a collaborative cell. You only sacrifice speed during the brief moments a human actually needs to enter the zone.
Frequently Asked Questions
Does a collaborative robot require physical safety fences? A cobot does not require physical safety fences if a documented risk assessment proves its operating force, speed, and tooling fall below ISO/TS 15066 injury thresholds. If the payload is sharp, toxic, or excessively heavy, you will still need fencing regardless of the robot's collaborative rating.
What is the maximum speed a collaborative robot can move? Collaborative robots typically operate at a maximum speed of 1,000 millimeters per second when working in close proximity to humans. Speeds can safely increase up to 2,500 millimeters per second or more if area scanners confirm the operator has left the defined work zone.
Who is legally responsible for cobot safety compliance? The final system integrator or the business installing the robot holds the legal responsibility for conducting the risk assessment and ensuring the entire cell complies with machinery directives. The robot manufacturer is only responsible for the safety rating of the bare arm.
How often do I need to update my risk assessment? You must update your risk assessment any time you change a core variable in the application. Changing the end-effector, increasing the payload weight, altering the layout of the cell, or moving the robot to a new task all require a fresh evaluation of the hazards.
Your first step in setting up a safe cell is to evaluate the end-effector and the payload. Before you spend time tuning robot arm speeds in the software, look at the geometry and weight of the part the robot carries-that single variable dictates every safety limit you will need to set.