The uncontrolled ejection of a workpiece, a tool or parts of it can cause a perforation of the safety guards of machine tools with severe consequences for the operator. Therefore, experimental tests have been conducted in Germany and Italy during the last two decades in order to design specific safety guards with sufficient penetration resistance. There are many parameters influencing the penetration behaviour: material of the target and its delivery condition, size, weight and shape, trajectory and impact angle of the projectile. This part 1 of the article describes how impact tests are being performed for different machine standards at IWF and INAIL laboratories. The assumptions and simplifications of the results are discussed on the back-ground of the existing database. The deterministic interpretation narrows several significant influences on the results of the impact tests to a single test arrangement. It is not considered that the empirically determined penetration resistance, even in an accurate test mounting, has a statistical variation. Based on results of the IWF, it is shown that there is a considerable difference between a deterministic and a probabilistic interpretation. Consequently, a probabilistic review of existing design guidelines is given by focusing on a critical example with a reasonable statistical fundament: the perforation of a 12 mm thickness polycarbonate guard. In the paper an explanation of how a commonly known “safety factor” seems to be the answer to ensure backwards compatibility with existing standards that is crucial aspect to be taken into account for the machinery manufacturers.

Probabilities in safety of machinery - risk reduction through fixed and moveable guards by standardized impact tests, part 1: applications and consideration of random effects

LANDI, LUCA;
2017

Abstract

The uncontrolled ejection of a workpiece, a tool or parts of it can cause a perforation of the safety guards of machine tools with severe consequences for the operator. Therefore, experimental tests have been conducted in Germany and Italy during the last two decades in order to design specific safety guards with sufficient penetration resistance. There are many parameters influencing the penetration behaviour: material of the target and its delivery condition, size, weight and shape, trajectory and impact angle of the projectile. This part 1 of the article describes how impact tests are being performed for different machine standards at IWF and INAIL laboratories. The assumptions and simplifications of the results are discussed on the back-ground of the existing database. The deterministic interpretation narrows several significant influences on the results of the impact tests to a single test arrangement. It is not considered that the empirically determined penetration resistance, even in an accurate test mounting, has a statistical variation. Based on results of the IWF, it is shown that there is a considerable difference between a deterministic and a probabilistic interpretation. Consequently, a probabilistic review of existing design guidelines is given by focusing on a critical example with a reasonable statistical fundament: the perforation of a 12 mm thickness polycarbonate guard. In the paper an explanation of how a commonly known “safety factor” seems to be the answer to ensure backwards compatibility with existing standards that is crucial aspect to be taken into account for the machinery manufacturers.
2017
9781138629370
File in questo prodotto:
Non ci sono file associati a questo prodotto.

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11391/1407655
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 9
  • ???jsp.display-item.citation.isi??? ND
social impact