Written by A machine safety risk assessment can look complete while still overlooking hazards that appear only during setup, cleaning, maintenance, fault recovery, or product changeover. The most visible moving parts are usually reviewed first, but safe operation depends on the entire machine lifecycle and every interaction between people, equipment, and process.
This guide focuses on commonly missed topics and practical questions that engineering, production, maintenance, and quality teams can use when reviewing a new or modified machine.
Start with the full range of machine activities
A risk assessment should cover more than automatic production. A machine may be safe during its normal cycle but create significant exposure during activities that occur less frequently. List each operating mode and task before identifying protective measures.
Include these operating situations
- Automatic and semi-automatic production
- Manual loading, unloading, and part orientation
- Setup, adjustment, and format changeover
- Cleaning, inspection, and quality checks
- Fault finding and jam removal
- Tool change, lubrication, and planned maintenance
- Commissioning, testing, and decommissioning
Rare tasks deserve particular attention. Their low frequency does not remove the hazard; it can make the task harder to perform consistently because operators and technicians have less routine familiarity with it.
Overlooked hazard 1: access during setup and recovery
Guarding designed around automatic production may not address what people need to do when the machine is stopped. Operators may need to reach into a working area to remove a rejected part, position a component, clear a misfeed, or verify a fixture.
Ask whether the task can be completed without entering the hazard zone. If access is necessary, define the intended method rather than relying on informal workarounds. Consider the location of access points, visibility, controls, safe stopping behavior, and the possibility of stored or residual energy.
Access should also be considered around tooling, conveyors, transfer mechanisms, press areas, clamps, and inspection stations. A narrow opening or poorly positioned door can encourage bypassing or reaching through a guard.
Overlooked hazard 2: unexpected restart and residual energy
Stopping the automatic cycle is not always equivalent to making the machine safe. Motion may continue because of inertia, pneumatic pressure, gravity, electrical energy, spring force, vacuum, hot surfaces, or an elevated load.
The assessment should distinguish between:
- A command to stop the process
- A controlled stop that brings motion to a defined condition
- Isolation of energy sources for work inside the hazardous area
Review what happens after a power interruption, emergency stop, guard opening, controller reset, or communication fault. Can the machine restart as soon as a guard is closed? Does a technician have a clear way to confirm that motion and stored energy have been removed? These questions should be answered for each relevant operating mode.
Overlooked hazard 3: bypasses, defeat, and poor visibility
Protective devices can become ineffective if they are easy to bypass or if normal work is difficult with the protection in place. A risk assessment should examine how a person might defeat a guard, mute a sensor, hold a control, or use a tool to reach a hazardous point.
This does not mean assuming improper behavior by every user. It means considering foreseeable behavior when production targets, blocked material flow, or frequent nuisance stops create pressure to continue operating.
Check whether operators can see the relevant area from the control position. Limited visibility may lead to repeated starts, additional personnel entering the area, or reliance on verbal signals. Where visibility is insufficient, the machine design may need improved access control, indication, observation, or operating procedures.
Overlooked hazard 4: interfaces between systems
Machines rarely operate in isolation. A risk assessment can miss hazards at the boundary between a machine and its surroundings, such as a conveyor, robot, tester, press, laser marking unit, or upstream and downstream equipment.
Review the interface conditions
- Which machine controls the shared movement or transfer?
- What happens if one system stops while the other continues?
- Can a person enter through an adjacent machine or open side?
- Are safety-related signals exchanged clearly and consistently?
- Can maintenance personnel isolate one system while another remains energized?
Material transfer can also create pinch, crush, and unexpected movement hazards at handover points. The physical gap between machines, access doors, and the reach envelope around the interface should be reviewed rather than treated as a simple connection detail.
For automation architecture, documenting field devices, control functions, and failure responses early can make safety discussions more concrete. The considerations involved in selecting PLC and field equipment can support this broader review, although safety functions require their own engineering evaluation.
Overlooked hazard 5: software, sensors, and abnormal states
Risk assessments often focus on mechanical hazards and give less attention to control logic. Yet software determines how the machine responds to conditions such as a missing part, an incorrect sequence, a sensor failure, a communication loss, or a reset request.
Consider the machine state when:
- A sensor remains permanently active or inactive
- A part is present in an unexpected position
- A cylinder or axis does not reach its expected position
- A network connection is interrupted
- An operator resets a fault after changing the physical condition
- A recipe or product format is changed
For each condition, define what the machine should do and what the user must verify before restarting. A fault message alone may not be sufficient if the hazard remains accessible or if the cause of the fault is unclear.
Overlooked hazard 6: tools, fixtures, and product variation
Jigs and fixtures can introduce hazards that are not obvious in the main machine layout. Clamping points, locating pins, ejectors, movable nests, and manually inserted tools may create pinch or impact points during loading and adjustment.
Assess the complete range of products, tolerances, orientations, and allowable tooling conditions. A component that is slightly distorted or incorrectly positioned may require more manual force or cause a clamp to move differently than expected.
Fixture design should support correct positioning and reduce the need for hands to remain near moving components. A detailed review of jig and fixture repeatability can also help identify situations where misalignment, excessive adjustment, or manual intervention may occur.
Overlooked hazard 7: ergonomics and human factors
Machine safety is not limited to preventing dramatic injury scenarios. Repetitive reaching, awkward posture, high insertion force, poor lighting, noise, heat, vibration, and difficult access can influence how safely a person performs the task.
Ergonomic problems may also increase the likelihood of bypassing a guard or skipping an isolation step. Review the real working position, not only the position shown in a CAD model. Observe how operators handle parts, read instructions, remove scrap, and respond to minor faults.
Controls and information should be understandable at the point of use. Labels, status indications, reset controls, and maintenance instructions should help users distinguish between a stopped machine and a machine that has been made safe for intervention.
Overlooked hazard 8: changes after commissioning
Safety can change when the process changes. New products, different tooling, revised cycle sequences, added inspection steps, modified conveyor speeds, or software updates may introduce new access or interaction risks.
Define a change-review process before modifications are made. The review should consider whether the existing assessment, protective devices, instructions, training, and verification activities remain suitable.
Production performance should not be separated from safety decisions. A design review that examines OEE losses during machine design can be combined with questions about frequent stops, manual recovery, and the behaviors those losses may encourage.
A practical review checklist
Before closing a machine safety risk assessment, ask the following:
- Have all operating, maintenance, cleaning, and recovery tasks been listed?
- Can every hazardous area be accessed, intentionally or unintentionally?
- What energy remains after a stop, and how is it isolated?
- What happens after a fault, reset, power loss, or communication failure?
- Can protective measures be bypassed during foreseeable work?
- Have machine-to-machine interfaces and shared access areas been reviewed?
- Are fixtures, tooling, product variation, and misloaded parts included?
- Can operators see the hazardous area while starting or resetting the machine?
- Have ergonomics and human factors been considered?
- Is there a defined review method for future modifications?
Conclusion
The most useful risk assessment is not a one-time document prepared only for design approval. It is a structured examination of how people will use, adjust, maintain, and recover the machine throughout its life.
By reviewing abnormal states, residual energy, interfaces, fixtures, visibility, ergonomics, and future changes, engineering teams can identify risks that a basic automatic-cycle review may miss. Protective measures should then be selected and verified according to the machine’s actual hazards, operating modes, and applicable requirements.