Can cobots securely take over repetitive tasks
Can cobots securely take over repetitive tasks
Omron, a leader in industrial automation, highlights how industry safety standards and solutions enable companies to gain the maximum value from collaborative robots (cobots) within collaborative workspaces.
Cobots are a key aspect of Industry 4.0 and the “factory of the future”, as they can be used in a wide range of industrial applications. Because they have various integral safety features, they can work with or near people and can also adapt easily to changing needs. This means that the productivity of many repetitive tasks can be significantly increased, enabling manufacturers to reap the benefits of a high return on their investment.
The safety features of cobots include a lightweight body, collision detection technology, and minimised pinch points. However, further safety measures might still be needed for specific applications, including the end effector (a device that attaches to the end of a robot’s arm to allow it to interact with its environment), the product, and other equipment in the collaborative workspace (a safe space where robots and people can work together).
For a cobot application to be successful, it must incorporate safety considerations based on comprehensive risk assessments.
Safety standards
Cobots are more compact than conventional robots and incorporate force and speed monitoring capabilities. When fitted with safety devices that detect anyone entering the collaborative workspace, they can often work at higher speeds when people aren’t present, which helps to maximise throughput.
ISO 10218-1, ISO 10218-2, and ISO TS 15066 are key safety standards that define the safety functions and performance of cobots.
The latter sets the force and speed monitoring of the cobot based on application data, human contact area, and workspace hazards. There are two types of human contact: transient (non-clamping contact) and quasi-static (involving situations that can cause a body part to be clamped). Manufacturers who aren’t familiar with the requirements of ISO TS 15066 can hire a safety assessment provider to make the calculations, take the measurements, and recommend improvements to the safety of the collaborative application.
ISO 10218 and ISO TS 15066 also guide cobot teaching. Many cobots, such as Omron’s TM Series, use intuitive “hand guiding” mechanisms for teaching new tasks. This avoids the need to program the specific movements of the robotic arm. The hand-guiding mode monitors force and speed so that the teaching process complies with safety standards.
Safe teaching and operation
Before teaching, the robot must be stopped before the operator enters its workspace, even if its force- and speed-limiting functionality has been activated. Alternatively, a safety device (such as an area scanner) must carry out a protective stop as soon as the operator is detected.
The operator can use a simple trigger, button, or mode selection to activate teaching if safety force and speed monitoring are in operation. If not, a three-position safety enable is required. According to the safety standards, the teaching mode transition must be deliberate, and must not lead to any unexpected motion or create additional hazards. The operator must be aware of surrounding equipment and possible safety issues at all times. To enhance operator safety, it’s possible to enforce motion limits, such as space and soft axis limits.
Before the operation, the operator must vacate the safeguarded space. This can be verified by safety sensors or additional operator verification. Intentional mode selection is needed to re-enable the robot for operation.
Safety in the collaborative workspace
Cobots operate near other potentially dangerous equipment, making it imperative to list and map out all additional equipment in the collaborative workspace (which must be marked). Each device must be assessed for potential hazards and for safety sensors that could prevent human and equipment damage.
Non-collaborative safety-rated equipment that might need safety devices includes material handling, tooling, grippers and actuators, and machines. Safety devices can usually be integrated easily into a cobot application.
Several solutions can be used to safeguard the collaborative workspace. In open areas and applications with low hazards, these include safety area scanners and mats. In gated or limited areas with more hazardous applications or high-speed operations, safety light curtains and safety switches can be used. In areas with active hazards, or operations that could cause a hazard, operators can enable a dead man’s switch, which automatically turns off if the user stops exerting pressure on it.
For maximum safety in collaborative operations, manufacturers must validate the safety of their cobot applications across all operations. There are some guidelines to follow when evaluating the safety of a robot while performing a given task with a human operator. Some dangers, such as drive and power hazards, might still exist even if the robot isn’t moving.
Operator safety
To protect operators, before starting a cobot or recovering from an emergency stop there must be an intentional act to enable the robot. For example, when an operator activates an e-stop, it should not be possible for the robot to re-enable automatically; it should first need verification from a second operator.
During the design and safety setup, hand guiding must only be allowed if the robot has stopped, there has been intentional mode selection, and speed and force monitoring is active. If hand guiding is activated without a stop command or safety input, this should initiate a safety stop and fault.
For the automatic operation of a cobot, the operator must make an intentional mode selection that requires all safety devices and conditions to be validated. For validation, a safety assessment review should be made of the surrounding areas and equipment, and a safety remediation service should be performed if necessary. Safety service groups should make an onsite inspection of equipment safety, confirm certifications, verify safety parameter settings, and document the completion of the validation.
Specific safety considerations
Machine tending: Experts who have completed many inspections and safety assessments report that machine tending applications are one of the industry’s top safety concerns. For maximum safety, manufacturers should use a safety-rated gripper to protect operators against injury. They should also investigate whether the product presents any dangers (such as extreme heat or sharp edges).
Material handling: Material handling applications that benefit from cobots include picking, packing, palletising, and sorting. For safety considerations, the wide use of these applications makes them a site-specific solution. Operators and other workers often move or transport other materials around the cobot, so additional planning is needed to avoid hazardous contact.
Safety-rated grippers are currently rare: manufacturers tend to use pneumatic grippers, with potential safety issues relating to impacts and the loss of power or suction. Application designers must also investigate whether the product presents any dangers that could cause problems if it is dropped.
Assembly: Assembly applications that use cobots often involve special tooling and close collaboration with operators, while also requiring high-speed operation zones. The extensive variety of custom end-of-arm tooling makes these applications especially complex. If multiple robots are involved, application designers must carefully coordinate the safety solutions for each one.
For all three of these areas (machine tending, material handling, and assembly applications), it’s very important to review the entire area for the risk of an operator being trapped or clamped by the robot or nearby equipment, and for any heavy or hazardous products.
Other considerations for all three areas include:
- Should the safety controls of other machines be linked to prevent one from operating when another is in a safety stop condition?
- As cobots move from machine to machine and from application to application, how is their safety validated?
- Are there warning zones for the operator that indicate hazards or operation interference?
Conclusion
Cobots are usually considered safe for use with people. However, they still need risk assessments throughout to ensure the safety of human operators. Manufacturers need to consider all of the potential hazards associated with hand-guided teaching, as well as possible issues when the robot is involved in an emergency stop.
Designers of automated machine tooling, material handling, and assembly applications should look at all of the interactions between the cobot and the human operator, along with the risks of clamping or entrapment, as well as the dangers from end-of-arm tooling due to high heat, sharp edges, or other hazards.
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