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Safety Concepts For Machine Tools

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Safety Concepts For Machine Tools
Safety Concepts For Machine Tools

No doubt: The Machinery Directive (MRL) from 2006 is considered to have positive effects on the industry. It should have made a significant contribution to standardizing security standards within the European Union and thus generating EU added value. The EU Commission is currently planning a new version of the directive. The harbingers of text cause unrest among companies and associations: while the objectives of the revision, such as adapting to technical progress, may still be approved, the crux lies in the details; this applies above all to machine tools.

Machine safety as a differentiator

For Eberhard Beck, head of control technology at the machine tool manufacturer Index-Werke and member of Working Group 3 "Safety Technology" at the VDW (Association of German Machine Tool Builders), it is clear that effective and productive machines can only be developed if manufacturers have all technical properties and functions through measurements and Know and document analyzes. This also includes machine safety. In this way, differentiation features on the market can be tapped and communicated successfully. Beck's clear position: "Overall, I see the high safety requirement as an advantage rather than a disadvantage of the German machine tool industry."

Note: The Metav Safety Day should take place on March 10, 2020 at the Metav. Due to the corovirus Covid-19, the fair has been postponed. We provide information about the latest dates in this article

Increase security continuously

The VDW, representing the interests of the German machine tool industry, has developed its own strategy to awaken understanding of the special practical aspects of machine tools in standardization processes - which is not always easy, as experts now complain about when revising the machine directive. On the other hand, it is about preparing key machine tool safety issues with experts from member companies, suppliers and customers and thus continuously increasing industry standards that can also be anchored in standards. "Security is not a property, but a process," emphasizes Dr. Alexander Broos, head of the research and technology department at VDW.

Machine safety user meeting

Machine safety is an important issue: the correct standards must be taken into account and the requirements of the Machinery Directive must be complied with. The machine safety user meeting supports developers and designers to ensure the functional safety of machines and systems.

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In order to be able to achieve real (personal) safety when working with machines, "must be constantly checked, rethought and further thought", confirms Eberhard Beck. Every near-accident or accident that becomes known in the course of machine use must be taken into account and checked in a safety-related manner in order to correct it if necessary. This is the only way to continuously increase machine safety and to ensure "that the simultaneous occurrence of a large number of unexpected hazardous situations in terms of personal safety can be managed." Eberhard Beck draws the motivation for himself to work for the VDW Engage in security technology. The work in the working group serves to exchange experiences and, as it were, as a “catalyst”, he notes.

Scientific support indispensable

Since it is no longer just about continuous improvements, but rather about demonstrating the probability of a critical event occurring (probabilistic approach) and assessing the residual risk, cooperation with universities and research institutes is also being promoted. Previous studies have examined, among other things, how the use of guards can lead to a significant reduction in the safety risk or what options are available to minimize the risk of a gravity-loaded axle, for example.

While on the one hand, the manufacturer side, investigations are initiated and supported by the VDW, on the other hand, the customer and user side, the professional associations are on the way with their own research projects. Ideally, the experts will come to the same results, which will then be jointly promoted internationally for recognition. Christian Adler, head of the testing and certification body for surface technology and lifting gear of the Wood and Metal Trade Association (BGHM), Hanover, traveled to Tokyo with the VDW security expert Heinrich Mödden at the end of January to advertise a proposal for dimensioning protective devices on grinding machines.

Seminar tip

The seminar "Basic knowledge of the Machinery Directive" gives manufacturers and operators the necessary basic knowledge about current developments and requirements in product safety.

Safe and economical at the same time

"The starting point of the problem was that the previous interpretation convention was completely exaggerated and could hardly be implemented," said Adler, which meant that the standard was simply not observed in practice. With its own study, the BGHM was able to demonstrate that the housing does not have to be so massive, since it can also deform without losing its security effect. Christian Adler will present the developed proposal at the Metav Safety Day in Düsseldorf. Basically, he is of the opinion that "it makes no sense to ask for the perfect protective device if the machine cannot be built for practical or economic reasons".


What is machine safety? Definition, standards & examples

Of course, economic considerations are paramount when designing a machine. "First and foremost, a machine has to do what it is purchased for," says Dr. Alexander Broos the customer view, "and that must be economical." The balancing act between market and security requirements takes place in a field of tension that changes "daily", as the VDW expert says. For example, after an accident caused by an imported, non-standard machine, the call for higher safety standards for European products becomes loud.

Opinions differ on cybersecurity and AI

New factual explosiveness is currently arising from the fact that the topics of cybersecurity and artificial intelligence should be included in the reform of the machinery directive. Broos believes that there is an understandable concern behind mapping technical progress, but issues such as process optimization through digitization and machine safety must be separated: "After all, a machine does not become unsafe if the machining process is optimized using AI methods."

The confusion of the terms safety and security - which cannot be distinguished in the German translation "safety" - will be clearly separated at Metav 2020 in two different events. Simply put, cybersecurity is about protecting the machine from human attacks. At Safety, the focus is on protecting people from the machine - or themselves.

Seminar tip

The seminar "Safe retrofitting of machines and systems" helps with the practical planning of retrofits and conveys the most important requirements for document verification.

Human-machine interaction hazard

A major problem remains that accidents on machine tools occur very rarely, but then, often caused by operator errors, can lead to very serious, if not fatal, injuries. The most important thought is therefore how to protect the "source of error" from yourself. In addition, the three-stage risk minimization strategy according to ISO 12100 says that an inherent, i.e. coherent, safe machine design must be the first priority. Protective measures and supplementary protective measures come in second place. And only when the first and second stages have been fully applied and relevant residual risks remain, is it about instructions and user information.

At the Metav Safety Day, the subject area of human-machine interaction will take up a lot of space. The greatest dangers arise, for example, from errors in the clamping process and the resulting flying parts as well as from entering the protected area of a machine that is still working, or through manipulation.

Supplementary information on the topic of VDW Technology Day - Safety technology on machine tools with changing framework conditions

10 am welcome

10.10 am Upcoming revision of the machinery directive

10.40 a.m. risk assessment and evidence of a tolerable residual risk

11.30 am Success principles for security

12.20 p.m. lunch break

1.00 pm Success principles for security

2:40 p.m. Legal aspects

Vertical turning under the safety magnifying glass

Dr. Volker Wittstock, research assistant at the Professorship for Machine Tool Design and Forming Technology at Chemnitz University of Technology, tested the safety-related problem of vertical turning in milling machines with a group of trainees. He observed processes, analyzed assembly errors and calculated the human error probability. This gave rise to the research topic "Recording and comparability of human and technical reliability for improved workpiece clamping in vertical turning - MTZ turning", with which he applied through the VDW research institute for funding from the Association of Industrial Research Associations (AiF). Work on the project will start in early March 2020.

Seminar tip

The seminar “Risk assessment and operating instructions” helps to implement the most important requirements of the Machinery Directive 2006/42 / EC.

According to Wittstock, the aim is to develop a new method of assessing the cause-and-effect relationship, which can arise if the manual workpiece clamping fails and thus the unwanted release of workpieces. The solution is primarily intended to support small and medium-sized enterprises (SMEs) that are characterized by manual or partially automated production.

Knowledge of security-relevant relationships

The planned user tests, in which as many companies as possible should participate, identify weaknesses in human-machine interaction, says Wittstock. He sees starting points here to improve instructions or the general knowledge of security-relevant contexts, for example by prioritizing. At the Metav Safety Day, Wittstock should certainly be asked whether this knowledge is then preferably transmitted via mobile phone, screen on the machine or even via virtual reality (VR). There are still no clear approaches, he says, especially since the requirements of the new machinery directive also play a role. In any case, a digital operating manual would allow very large scope. Operating instructions on paper or as PDF, as is currently also provided in the new version of the Machinery Directive,don't do that. (jv)

Note: The Metav Safety Day should take place on March 10, 2020 at the Metav. Due to the corovirus Covid-19, the fair has been postponed. We provide information about the latest dates in this article

Machine safety dossier 2019

Functional safety in all facets

* Cornelia Gewiehs is a freelance journalist, Rotenburg (Wümme).

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