What you Need to Know about Safety Norms before you Purchase a Collaborative Robot

One of the main concerns for manufacturers looking to employ collaborative robots in their production line is certainly the associated safety measures and risk assessment. It is not easy though to have a clear picture of the world of directives, norms, and standards whose complexity may slow down the innovation process. In the following, we want to give an overview of the main concepts, regulations, and standards that applies to robotics in general and to collaborative robotics in particular.

The European Machinery Directive is the main document for all European countries that set common terms and objectives for working conditions in manufacturing plants. A directive of the European Commission has to be transcribed in actual laws by every member of the community in order to be compliant with the directive. The set of standards and laws for the accomplishment of the objectives of a directive are set independently by each member of the community, leaving some freedom of implementation to each country.

In practice along with European Directives the three recognized European Standardization Organizations (ESOs): CEN, CENELEC, ETSI publish norms and standards (EN = European Norms) to support the directives with concrete ways to attain compliance. Although the compliance to standards is not mandatory in practice it is the most straightforward way to follow the guidelines and prove the commitment to European Directives. Thus the standards ENs are often translated into national standards and laws and become the actual implementation of the directives in national administrations.

European Norms published by the Standardization Organizations are usually referred to as harmonized standards and are often in accordance with international standards drafted by organizations such as the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC), so it is common that norms are often denoted EN/ISO or EN/IEC meaning that they refer to international standards. The group of ENs that concerns a particular directive is usually drawn up and published on the Official Journal of the European Union (OJEU). For the Machinery Directive, this is the related notice published on the OJEU. In the framework of norms pertaining to a directive, these are usually categorized into three subgroups: types A, B, and C norms.

Type A: these are basic safety standards that provide design principles and techniques to ensure the health and safety of products and/or workplaces in the framework of a particular European Directive. Concerning the Machinery Directive the corresponding Type A harmonized standard is the EN/ISO 12100.

Type B: these are generic safety standards that concern specific aspects or components of machinery and thus can apply to a wide range of cases. The Type B category is further divided into two subcategories:
B1 type: these standards are related to specific aspects such as safety distances, surface temperature, safety-related control systems (EN/ISO 13849-1), electrical requirements (EN/IEC 60204-1), etc.
B2 type: these are related to particular safety devices like safeguards, pressure sensitive devices, etc. To this category belong also the many standards for EMC that are grouped by function and environment.

Type C: these are standards for specific types of machines and applications such as textile, sewing machinery. The standard for robotics applications also belongs to this class (EN/ISO 10218). Type C norms, in turn, specify which A and B Types standards that apply to the particular machine addressed and in some cases may prescribe focused modification to those. In summary, the hierarchy of priorities is C, B, A.

For what concerns cobotics applications, the current normative is contained in EN/ISO 10218-2 where collaborative robots are defined as an industrial robot that can be used in a collaborative operation. The document provides the requirements for collaborative applications and discusses four techniques for collaborative operations:

• Safety-rated monitored stop
• Hand-guiding operation
• Speed & separation monitoring
• Power & force limiting

These are the current ways with which industrial robots can be used in collaborative operations. Since the collaborative operations are constantly growing in importance and the space reserved to those is just a small portion of EN/ISO 10218-2 subsequent work on collaborative robotics standardization have been carried out with ISO/TS 15066, released in 2016. This technical specification addresses collaborative robot system safety with a different philosophy with respect to EN/ISO 10218, as Roberta Nelson Shea, Convenor of the ISO Industrial Robot Safety Working Group (ISO/TC 299/WG 3), explains, “When working on the standards for safety of industrial robots (ISO 10218-1 and ISO 10218-2), a philosophical discussion arose. If an application will not hurt and injure a human, why not allow contact? As a result, ISO 10218 discusses four techniques for collaborative operation. Work on ISO/TS 15066 started with the idea that, if there were to be any incidental contact between human and machine, it shall not result in pain or injury.” [3]

The technical specification thus complements the current standards for collaborative operations and also expand the range of definitions and techniques used for a correct assessment and reduction of risks for these scenarios.
Despite ISO/TS 15066 is for now just a technical specification, its content is expected to be incorporated into the next review of ISO 10218 and it is already one of the first document that a manufacturer interested in collaborative applications should be aware of.

References:

[1] http://www.gt-engineering.it/en/Insights/machinery-directive-the-harmonised-standards

[2] https://blog.ansi.org/2017/10/iso-type-abc-structure-machinery-standards-ansi-b11/

[3] https://www.iso.org/news/2016/03/Ref2057.html

2019-04-29T09:11:16+00:00