5 min read
Protection and safety in automation with robots
Patrick Enderle
:
Nov 25, 2022 8:53:00 AM
One of the most important aspects of working with robots in the industry is safety. The guidelines for construction and operation primarily serve to protect the employees. Accordingly, industrial robots, modern Digital Robots, or Cobots may only be used in compliance with established guidelines and standards.
Every company that uses machinery has probably come into contact with the Machinery Directive 2006/42/EC at some point. It specifies the requirements for accident prevention that must be followed for finished (or unfinished) machines when they are used within the European Economic Area (EEA). Therefore, the directive also applies to various types of robots in the industry.
The extent of an information brochure from the German Social Accident Insurance (DGUV) – it comprises a total of 80 pages – illustrates how important and complex the implementation of this EU directive is for companies. It should be noted that the information provided by the DGUV is only a freely summarized version of the EU Machinery Directive, which is not legally or normatively binding. Experts in the risk assessment of industrial robots therefore rightly advise companies to orient themselves based on the Machinery Directive and ISO standards.
Industrial Robots, Digital Robots, Cobots: Safety always comes first
With conventional industrial robots, the importance of safety is evident at first glance: The huge machines, as known from industries like automotive, inherently possess a certain potential for danger due to their size and mass. However, automation is rapidly evolving, and thanks to smaller, more affordable, and flexible robots, it is now accessible to companies of all sizes and industries.
Additionally, the emergence of Collaborative Robots (Cobots) has brought safety to the forefront. In this case, humans and robots are meant to work directly alongside each other – without separating or non-separating protective devices. To minimize the risk of injury, strict regulations are imposed on Cobots regarding the limitation of power, speed, and force during collaborative operations. Otherwise, protective measures would also need to be installed for a Cobot.
On the other hand, innovative Digital Robots, which enrich automation as a fusion of powerful hardware, advanced software, and an Industrial Internet of Things platform, are legally and normatively treated as industrial robots.
Why is safety particularly important in robotics?
Unlike conventional machines, robots move freely in space. Previously programmed work areas are much more difficult for humans to assess compared to, for example, a press that is fixed in place and operates within a defined area. Additionally, powerful robots can achieve high speeds. Even Digital robots designed for payloads in the double-digit kilogram range have a force that is difficult to predict from the outside.
A robot that appears to be turned off can suddenly move from a waiting position when it receives a signal to continue a process. Improperly positioned tools or workpieces can be thrown around or fall. The paramount safety goal is therefore to prevent individuals from entering the working area of the robot system (for example, through fences, locked doors, or non-separating safety elements like light curtains).
What is the legal situation in Germany and the EU?
This is regulated by laws and standards. While the aforementioned Machinery Directive RL 2006/42/EG constitutes the binding legal basis, ISO standards with detailed descriptions help to comply with this legal framework. In Germany, the Machinery Directive adopted by the EU in 2006 is implemented in the Product Safety Act (ProdSG) and the Machinery Ordinance (9. ProdSV). In Austria, this is the Machinery Safety Regulation 2010. Switzerland also aligns itself with the EU directive through the Ordinance on the Safety of Machinery.
The most important safety standard for industrial robotics is ISO 10218, which, in two parts, describes requirements for robot manufacturers as well as plant builders and integrators for the complete robot system. It in turn refers to dozens of other standards for safety compliance. These include, for example, ISO 13875 (for safety distances and fences) as well as ISO 13855 (for non-contact protective devices such as laser scanners).
Furthermore, for Cobots, the technical specification ISO TS 15066 applies. It provides detailed descriptions of the requirements for collaborative work. It goes into great detail, specifying limits for nearly 30 body zones from head to toe, for instance, excluding contact possibilities at head height. It must also be ensured that the working surface is free of risks in Cobot mode according to ISO TS 15066 (avoidance of sharp or pointed areas and edges) and that there are adequate coverings and/or cushions available.
How does the risk assessment for a robotic system work?
For companies, it is crucial to understand their automation application as a whole in order to ensure absolutely safe operation. The application includes not only the actual robot but also all other components, such as tools like grippers, peripherals, and protective devices. Additionally, the work environment and workpieces must be thoroughly considered for a risk assessment.
A robotic system can only be operated when the requirements described in the ISO standards of the EU Machinery Directive are ensured. Machine operators are ultimately responsible for avoiding any endangerment of individuals.
Validation and verification options for a robot according to ISO 10218-2
- Visual Inspection
- Practical Tests
- Measurements
- Observation during Operation
- Examination of Application-Specific Schemes, Wiring Diagrams, and Design Documents
- Examination of Safety-Related Application Software and/or Software Documentation
- Review of Task-Based Risk Assessment
- Examination of Assembly Drawings and Documents
- Verification of Specifications and User Information
The advantage for businesses lacking the time or expertise to navigate through the jungle of guidelines and standards: Reliable robot manufacturers, firstly, provide non-binding advice before purchase and assess the desired application for its safe feasibility. Secondly, they inform in the user manual about the significance of the EC Declaration of Conformity and CE marking. This important mark demonstrates that all safety-relevant requirements of the Machinery Directive are met, and the user can operate the robot system. Competent robot providers, thirdly, assist companies in meeting these requirements.
Additionally, there are already CE-compliant quick start systems available on the robot market in various configurations, allowing for immediate work in the intended manner.
What safety measures does a Digital Robot come with by default?
Upon delivery of the industrial robot, users have important safety measures at their disposal. A key component is an externally controllable operating panel, which allows the robot to be controlled from outside its working area. These operating panels feature both an emergency stop button and multi-stage approval buttons for programming. If, out of shock or carelessness, the button is not held in the intended position – for example, in the middle position for three stages – the robot would immediately stop.
A safety controller further enhances protection. It maintains safety-relevant functions of the robot system even in the event of a disruption. While some robot manufacturers require an additional safety controller for connecting with external machines and/or components, others manage to integrate secure communication into the robot control system focused on Performance Level d.
Additional safety devices – such as laser scanners or light barriers – can be directly integrated and configured through the robot system. This is a real advantage for automating companies, as these safety devices can firstly be deployed quickly, and secondly, employees do not need to acquire knowledge about an additional control system.
How is a robot programmed and operated safely?
To ensure the setup or verification of a new program is risk-free, industrial robots have multiple operating modes. Depending on the manufacturer, this can be set using keys or switches. For example, in manual teach mode, an acknowledgment button must be held down, and the speed during programming is reduced.
Only when the entire protected area is secured may an industrial robot operate in automatic mode. The start of automatic mode must occur from outside the protected area. If a person enters it, a safety stop is triggered.
When are the workspaces of industrial robots considered secured?
To prevent people from entering the robot workspace unintentionally, isolating safety devices are an obvious solution. Examples of these are enclosed robot cells and/or mesh fences. In practice, for robots with lower payload capacities, such as Digital Robots, polycarbonate windows have proven effective.
Security can also be ensured through non-separating safety devices, such as laser scanners. Because people can enter this area, a safety distance must be maintained. It ensures that the system stops before the person reaches potentially hazardous areas in the installation.
Hier kommt die bereits erwähnte ISO-Norm 13855 zum Tragen, mit deren Hilfe Anwendende den Sicherheitsabstand berechnen können. Die Formel richtet sich nach der Annäherungsgeschwindigkeit eines Menschen (K) und wird multipliziert mit der gesamten Nachlaufzeit des Systems bis zum Halt in Sekunden (T). Addiert wird dieser Wert mit dem Eindringabstand eines Körperteils (C) in Millimetern. Also: K x T + C
Here, the aforementioned ISO standard 13855 comes into play, which allows users to calculate the safety distance. The formula is based on the approach speed of a person (K) and is multiplied by the total response time of the system until it comes to a halt in seconds (T). This value is then added to the intrusion distance of a body part (C) in millimeters. So: K x T + C.
How is safety ensured outside of robot operation?
So, there are a whole range of measures in place to ensure that you can use the easily integrable and flexibly deployable Digital Robots safely. The advantage of these innovative industrial robots is that they can be set up and put into operation very easily – by employees with the appropriate technical and electronic training. It is also their responsibility and/or that of their supervisors to inform the team about the status of the installation and to conduct regular risk assessments.