Machine tool safety is of paramount concern for manufacturers. Equally important are changes or additions to the safety practices outlined in the standards created by organizations like the VDW (German Machine Tool Builder Association).
This very association recently released a statement detailing the need for further clarification of safety functions, due to technology-specific differences in interpretation, under Type-B Standard ISO 23849-1. Under this standard, safety functions are given probability-referenced ratings as models for control chains.
This standard affects Type C Product Safety Standards, including:
- ISO 16089 for grinding machines
- ISO 16090 for milling machines
- ISO 23125 for lathes and other ISO standards.
Recently expanded company participation in the VDW’s “Safety engineering in metal-cutting machining” working group has increased the need for clarification even further, the organization stated. Presses and lasering machines were included under the working group’s scope, and as of yet have no standard requirements for safety functions.
Operating Modes
Operating modes are considered to be a controversial issue, as VDW cites trouble-shooting and maintenance to be problematic when safety features are routinely stepped around, using a “Golden Tongue” key – an object or process used to manipulate machines into believing that the guard door is locked and closed, bypassing security.
“The accident risk, according to surveys conducted by the DGUV (German Statutory Accident Insurance Agency) is approximately 10 to 20 times higher than in undisturbed production operations,” VDW stated in a release. “Following nationwide consultations, the DGUV announced a position paper that so far is manifestly aimed only at machinery manufacturers.”
The DGUV paper is titled, “Instructions for manufacturers on risk assessment of machines and machinery systems with reference to the aspect of measures to counteract manipulation of safety features.”
To ensure a holistic approach, the VDW intends to present a harmonised standard on the organizations “Safety Day” at the EMO Hannover, on Sept. 19, 2017.
Internal Handling of Security and Machine Manipulation
In their release, VDW included expert insights from Peter Steger, a design engineer at Grob-Werke GmbH & Co. KG, located in Mindelheim, Germany.
In the questions and answers below, Steger addresses how the Grob company addresses the issues of occupational safety, machine manipulation using the “Golden Tongue” and how customers are encouraged to learn and practice the best safety practices.
Grob is acknowledged as a model company when it comes to occupational safety. How do you handle this issue internally with your own machine operators?
Steger: “For working safely with machine tools, it’s vital that the employees concerned are adequately briefed about the dangers involved in working with machine tools and about the protective measures for averting these dangers. Apart from the operator training courses themselves, our operators receive regular briefings on the subject of health and safety.
Besides general instructions on safety-compliant behaviour, the insights gained from the relevant risk assessment of the workplace, and the equipment used there, are incorporated. In this case, for example, the hazard-related factors when working with machine tools and the protective measures that have to be complied with. The protection concept for our operators is rounded off by additional information on-site, such as an operating manual for safety-compliant working with the machine tool.”
What about the instructors for the operators?
Steger: “We additionally send our forepersons to external seminars held by the Employers’ Liability Insurance Association, to raise their awareness of their managerial duties and remits – not least in regard to occupational safety. Above all, our new young forepersons are being trained by outside lecturers, and are thus learning even more about the important role played by the duty of care for employees. The experience they gain in these outside seminars helps the forepersons, since they can utilise the tips in actual practice to optimum effect.”
It’s also a tip that customers should take on board?
Steger: “Definitely. What’s important for our people counts just as much for our customers.”
How does Grob train its customers?
Steger: “When we sell extensive production lines, we offer our customers training courses specifically tailored to the requirements of the customer concerned. For multi-purpose machines, we have a range of complementary training modules; these include process-compliant programming, helical interpolation and geometrical calibration, for example. We also, of course, always talk about how to handle the machines safely, and provide examples from actual practice.”
Could you cite a typical example?
Steger: “When our customers are already working with one of our machining centres, we show them ways and options for increasing their productivity. Thanks to our training courses, they become even more familiar with our machines, and learn how to operate them safely. New customers, too, benefit from our training courses, which contribute towards proactive safety and demonstrate efficient working practices. Various measures are presented for reducing the stress on machines and tools, shortening the make-ready times and ensuring full capacity utilisation at the machine. This in turn contributes towards upgrading quality levels. Working with machine tools, after all, stands and falls with the quality of the control system.”
How else do you support users in terms of occupational safety?
Steger: “We make sure that no hazards can be created by the machine when separating safety guards are opened, and that it can be operated without manipulating any protective features.”
Primarily concerning pre-production run validation: what regulations must be complied with in situations typical for production operations?
Steger: “The important ones are Operating 2 and 3 as EN 12417, plus in the future MSO 2 and 3 in accordance with FDIS ISO 16090 ‘Safety of Milling Machines’. MSO stands for ‘Mode of Safe Operation’ and FDIS for ‘Final Draft International Standard’. In these safe operating modes, the staff can safely operate a machine in many functions even when the door is open, using a portable device. They can try out movements in the machine, for instance, without manipulating the production line in any way.”
How do you proceed in your own production operations?
Steger: “For our own highly qualified personnel, we have internally defined the ‘Grob operating mode’, which goes beyond the functions of the normative operating modes MSO 2 and 3. These operating modes restrict operations by imposing limits, such as regarding the speed, for example. For everyday work in test runs, however, these limits are not very helpful. With the ‘Grob operating mode’, you can overcome these limits without manipulating the machine.”
You’re offering safety without any loss in speed, meaning without any impairment of productivity. Wouldn’t this function be of interest to customers as well?
Steger: “For them, there are already the normative operating modes MSO 2 and 3. We do, get asked to enable the ‘Grob operating mode’ for customers’ maintenance staff, as well. But given the ongoing standards situation, this is not permissible without appropriate measures and processes to be put in place by the customer concerned.”
What do you think about the use of electronic safety switches of Type 4 as defined in ISO 14119 “Safety of interlocking devices”, which protect the machine against manipulation using radio technology; for example, keyword RFID?
Steger: “Without a doubt, there is an interesting new trend towards highly encoded safety switches designed to preclude the possibility of manipulation. This signifies the end of the line for the ‘Golden Tongue’, a multi-purpose key for manipulating protective features, which enabled staff operators to make the control system erroneously believe that the guard door is closed and locked.”
What topics can visitors to the Grob stand at the EMO Hannover 2017 learn more about in terms of occupational safety?
Steger: “Visitors to our stand at the EMO Hannover 2017 will learn more about occupational safety, ergonomics and the relevant courses available. Our customer training team will be there on the spot and presenting courses designed to provide our customers with valuable tips on how to handle our machines.”
For more information, visit the VDW and EMO Hannover websites.