Work processes can also pose mechanical hazards, e.g. collisions of robots or parts of the tool or workpiece with the safety fence (for the causes, see article on restricted space). There is currently no normative or legal impact resistance of robot safety fences required for these scenarios. The energy of the moving robot parts, including tools, etc., is to be calculated according to the formulas for the energy and compared with the impact resistance of the protective fence (see figure). This energy value, often referred to as strength, is given in Joules or Nm.
The impact resistance determined in this way should not be confused with the basic stability of 115 J required by EN ISO 14120. This value applies to the assumption of a person falling against the safety fence from the outside (see post). The impact resistance in the event of a collision of robots or parts of the tool or workpiece with the safety fence shall usually be significantly higher than this value. Some manufacturers of machine safety fences specify values for impact resistance according to EN ISO 14120 in their data sheets.
In order to avoid collisions of robots or parts of the tool or workpiece with the safety fence, a so-called restricted space is usually provided. If this is not technically possible, the impact resistance of the safety fence can also be reinforced, for example, by installing steel profiles, so-called impact protection.
According to EN ISO 14120, only minor damage or deformation may occur during the test of the impact resistance of robot safety fences (see picture), which do not lower the effectiveness of the safety fence.
In addition to mechanical hazards, fixed guards of robot applications shall also protect people from other process-related hazards. These are, for example, hazardous substances such as welding fumes or radiation from welding arcs. In these cases, no safety fence is usually used, but a cabin that enables appropriate extraction and retains radiation.
In addition to the safety fences, other safeguards are usually necessary, such as safety doors (movable safeguards), light curtains and laser scanners (sensitive protective devices).
Like all other safeguards, robot safety fences must also be part of the periodic inspections at the user’s site. According to the German Betriebssicherheitsverordnung, the intervals of these tests are based on the results of the risk assessment. As a rule, it is 1-2 years. Safety-relevant damage to the safety fences or access interlocks must be repaired immediately.
Find more requirements for robot safety fences here
This article is a translation of German websites
