Cobot Risk Assessment: A Step-by-Step Process for ISO 12100 and ISO 10218

A cobot risk assessment identifies every hazard in a collaborative robot application, evaluates the severity and probability of harm, and determines which safety measures are needed to reduce risk to acceptable levels. It follows ISO 12100 methodology and is required by ISO 10218-2 before any cobot can operate in a shared workspace.

The risk assessment drives everything downstream: which collaborative mode to use, which body regions to test, what force limits apply. Skip it or do it poorly, and the entire compliance chain breaks. That’s not an exaggeration. Force and pressure testing without a prior risk assessment is measuring the wrong things at the wrong places. You end up with compliance documentation that covers contact scenarios that don’t matter while missing the ones that do.

Why the Risk Assessment Comes First

ISO 10218-2 is explicit: the risk assessment must be completed before the cobot installation is commissioned. This isn’t procedural formality. Without it, there’s no basis for any downstream safety decision.

The risk assessment is what tells you:

• Which body regions are realistically exposed to contact, based on where operators actually stand, reach, and work
• Whether contact at each point is transient (operator can recoil) or quasi-static (operator gets trapped)
• Which of the four collaborative operation modes applies: safety-rated monitored stop, hand guiding, speed and separation monitoring, or power and force limiting
• Which ISO/TS 15066 force and pressure limits govern each identified contact scenario
• Where to position measurement equipment during compliance testing

The scope of all downstream safety work comes from the risk assessment. For the standards framework that defines what each of those requirements means, see Collaborative Robot Safety Standards: ISO 10218 and ISO/TS 15066 Explained.

The ISO 12100 Process

ISO 12100 defines a five-step iterative process. The output of each step feeds into the next, and the process repeats until all residual risks meet tolerability criteria.

The three-step risk reduction hierarchy matters because the order is not optional. You cannot skip to a warning label if a design change would eliminate the hazard. ISO 12100 requires working through the hierarchy in sequence:

1. Inherent safe design: Change the robot path to eliminate the contact scenario. Reduce speed at the relevant point in the program. Modify tool geometry to remove sharp edges or protrusions. Change workspace layout to increase clearance from fixed surfaces.
2. Safeguarding: Apply power and force limiting (PFL) mode with validated speed and force settings. Add safety-rated sensors. Install physical barriers for contact points that can’t be addressed by design.
3. Information and training: Document residual risks, train operators, post warnings. This step only addresses what couldn’t be designed or safeguarded out. It’s not a shortcut.

Hazard Identification for Cobot Cells

Hazard identification is where most risk assessments go wrong. The common failure is doing it from a desk, looking at a CAD drawing or watching a video of the robot cycle. That approach misses what operators actually experience.

Walk through the cell physically. Stand where the operator stands. Reach where they reach. Watch the robot cycle at full speed from the operator’s position. The hazards that matter are the ones visible from that vantage point, not the theoretical ones derived from a process flow chart.

The main hazard categories for cobot applications:

For each identified hazard, record: what the hazard is, which operating mode it occurs in, which body region is realistically exposed, and what the realistic worst-case outcome is. Vague hazard descriptions produce vague risk estimates. “Robot hits operator” is not a hazard entry. “CRX-10iA arm segment 3 strikes operator’s forearm during return stroke at 250mm/s, quasi-static against conveyor rail at 600mm height” is a hazard entry.

Body Region Mapping

Every identified contact hazard gets mapped to one or more body regions from ISO/TS 15066 Table A.2. This mapping determines which force and pressure limits apply during compliance testing.

The mapping process follows the operator’s actual position and motion during the task:

1. For each identified contact point, determine which body part is realistically exposed given normal operator posture
2. Account for operator variability: seated versus standing, left-handed versus right-handed, operators at the 5th versus 95th height percentile
3. Consider the full range of motion the operator performs during the task, not just the nominal position
4. Map to the specific body region from ISO/TS 15066 Table A.2, not a generic category

A few mappings that are frequently wrong in practice: shoulder-height horizontal robot paths often expose the face and neck of shorter operators, not just the shoulder. Assembly tasks that require leaning in expose the torso to clamping against the robot base or tooling fixture. Foot exposure is common but often omitted entirely.

For the complete spring constant and force limit table per body region, see ISO/TS 15066 Body Region Force and Pressure Limits. That table is what connects your hazard map to the specific measurement setup for compliance testing.

Documenting the Risk Assessment

Documentation is where many technically sound risk assessments fail an audit. The analysis may be correct, but if it’s not documented in a form that demonstrates compliance with ISO 10218-2, it doesn’t satisfy the requirement.

The re-assessment trigger documentation is the element most consistently missing from risk assessments that were otherwise thorough. ISO 10218-2 requires it. In practice, it’s a short list: new end-effector, modified robot program, different workpiece type, changed cell layout, new or modified operator tasks, and any near-miss or incident. Write it into the document. It becomes the basis for your change management procedure.

One more documentation discipline: record the robot program version tested. When the program changes, the risk assessment must be updated and compliance testing repeated. Without the version reference, you can’t demonstrate that your assessment reflects the current installation.

Common Mistakes

The same errors appear repeatedly across cobot risk assessments, regardless of facility or industry.

Using a generic template without customization. Templates are a starting point. A risk assessment that reads identically for a FANUC CRX-10iA picking 2 kg aluminum housings and a Universal Robots UR10e performing circuit board assembly is wrong for both of them. The hazard identification must reflect the actual application.

Assessing only normal operation. Teaching mode is where most actual incidents occur. The robot is under reduced speed control, but the operator is inside the workspace and potentially in postures they wouldn’t use during production. Maintenance and cleaning modes have their own hazard profiles. Every mode needs its own section.

Assuming the cobot is inherently safe. Collaborative robot designs have built-in force and speed limiting. That doesn’t make the application safe. The application includes the tooling, the workpieces, the fixtures, the workspace layout, and the specific interaction tasks. All of those introduce hazards the robot’s internal safety system doesn’t address. The manufacturer’s risk assessment for the robot itself does not cover the application.

Excluding operators from the hazard identification. Safety engineers and manufacturing engineers often identify the mechanical hazards. Operators identify the behavioral ones: the awkward reach they make twice a shift to clear a jam, the place where they rest their hand while waiting, the shortcut they take when production is behind. Walk the cell with the people who run it.

Treating it as a one-time document. A risk assessment describes the installation as it exists at a specific point in time. When anything changes, the assessment may no longer be accurate. Define update triggers in the document and enforce them through change management.

Frequently Asked Questions

The risk assessment identifies what needs testing. The next step is performing those tests: measuring the actual forces and pressures at each identified contact point and comparing them against the ISO/TS 15066 limits for the relevant body regions. See the Cobot Safety Testing Guide for the measurement process, equipment selection, and documentation requirements.