SYN] Magazine
#3 | 2019

It isn’t all down to the Assembly Tool

Ergonomic Tightening – healthier Work for higher Quality

Good tools are certainly essential for high-quality bolted joints. However, the right accessories and, more recently, tightening strategies that can be precisely adapted to the individual application, also have considerable impact on assembly quality and operators’ well-being.

If we look back to the “good old days”, we find that assembly facilities were often loud and dirty. Noisy pneumatic impact wrenches released clouds of oil mist as their pneumatic motors needed to be lubricated. Even tools which were already equipped with silencers caused unavoidable noise as result of the impact process, for example if metal sheet resonated. This resonance causes noise and in some cases harmful vibrations. As an outcome, assembly workers could feel the results of their work in their hands, arms and joints when they had finished their shift. Early hydraulic nutrunners were also no real alternative because they were heavy, cumbersome and slow.

Good Impulses

Many things have now changed. Since the 1980s, impact wrenches have been increasingly replaced by impulse nutrunners which have less impact on the operator. In the case of impulse nutrunners, the torque required for tightening screws is generated and transmitted by an oil-filled pulse cell. This avoids the negative effects caused by metal-metal impact. Since the 1990s, the use of electronically controlled electric nutrunners has become increasingly widespread. They are also quieter and cause less vibration. For the past few years, there has been a boom in demand for cordless tools. These are available with a variety of accessories such as torque arms and reaction bars to further relieve the burden on the operator. 

„Developments to date have already brought considerable progress,” says Michael Kierakowicz, product manager for assembly tools. However, he is convinced that there is always a better way. “People used to think that ergonomic factors could have an adverse impact on productivity. As a result, the second-best solution for the operator was often implemented.” Fortunately, most companies now see productivity, ergonomics and quality as equally valid corporate goals, which is why the most significant improvements have been made more recently.

Half is not enough

According to a common saying among German craftsmen, with good tools, the work is already half done. Atlas Copco therefore produces better and better tools with low reaction forces and low vibrations. However, no one can be satisfied if only half the work is done. Kierakowicz says: “We invest about 6 percent of group sales in research and development, an above-average figure, in order to cover the second half and to offer holistic, user-friendly solutions.” Although conflicts may arise between ergonomics, process security and productivity, Kierakowicz is convinced that the combination of tried and tested assembly methods with innovative technology is increasingly resolving these conflicts.

Zero-fault assembly focusing on the worker

The product developers at Atlas Copco use cordless data transmission and the miniaturization of electronics for functions which were only visions for the distant future a few years ago. Kierakowicz talks about the impressive development of impulse nutrunner technology: “The spring-mass principle for softer pulses with significantly lower vibration and noise levels was a good approach. However, special software is now making good tools into very good tools. This way, we can offer lightweight, convenient assembly tools with a tried and tested ergonomic design that set new standards in terms of user comfort, productivity and assembly quality at the same time as being more precise and faster.” The combination of modern cordless technology with innovative tightening strategies allows a breakthrough towards optimum ergonomics and Industry 4.0.

This video shows how our dynamic tightening strategy works. This approach relieves the burden on the hand and arm system and drastically improves user comfort.

Turbocharging Production

TurboTight is a dynamic tightening strategy that detects the stiffness of the joint during tightening and calculates the energy required to reach the target torque with as little reactive torque as possible. In addition to many cable-connected nutrunners, the electric impulse nutrunner Tensor SRB is the first cordless Atlas Copco tool to use this trailblazing assembly strategy. Thanks to TurboTight, SRB cordless tools combine shorter cycle times with higher productivity and improved ergonomics. It also allows full documentation and traceability of all tightening operations. In addition to unambiguous LED signals on the unit, the operator receives specific feedback on tightening results via an integrated loudspeaker, ensuring greater safety and boosting workers’ confidence.

Powerful Tightening without reactive Torque

Many of Atlas Copco’s flexible cordless nutrunners and cable-connected electric tools are controlled using the Power Focus 6000 controller. With a SoftStop function, this controller can program all compatible tools for an especially soft shut-off with virtually no reactive torque when the target torque value is reached. “The SoftStop strategy is a further step in minimizing harmful forces on the user,” Kierakowicz emphasizes. He also presents another interesting strategy: “TensorPulse is a smart strategy that we have developed exclusively for electric nutrunners with pistol grips. With electric pulsing, it simulates the virtually reaction-free tightening process of the impulse nutrunners and further relieves the strain on operators.”

Power-Booster for Assembly Tools

Atlas Copco Tools’ turbocharger effect for battery impulse tools transfers the performance boost of Formula One to battery-powered tightening systems. “ActiDrive is a booster function that provides unprecedented peak performance for a short time for the completion of the tightening operation. Specifically, 18 V or 36 V batteries can deliver performance corresponding to 50 V without any damage to the battery or harmful effects on the operator. On the contrary, tightening operations are completed faster with less stress for workers thanks to shorter cycle times.

Torque Arms and Reaction Force Supports

The hardware and software solutions are supplemented by a comprehensive range of accessories providing effective possibilities for healthier working in the production environment. If nuts and bolts cannot be tightened by a pulse process, rotating tools are often used for higher torque values. In these applications, reactive torque is unavoidable. For good ergonomics, these harmful forces must be kept away from the operator. “The first possibility is to add a reaction bar to the tool. These aluminum, steel or carbon fiber bars are braced against the components during assembly. They provide support and absorb the reactive forces instead of the operator.” An even better solution is to install the nutrunner on an Articulated Arm (right). “Forces from 5 to 6,000 Newton-meters are diverted via this flexible torque arm, which also supports the weight of the tool. The operator does not need to carry any load and can concentrate entirely on the tightening process,” says the assembly tool product manager, emphasizing the benefits of this solution.

Guided Sockets and Extensions

In terms of ergonomics, even small items can make a big difference, Michael Kierakowicz knows. For example, sockets, bits and extensions are always subject to wear. “If wear becomes visible, these parts should always be replaced in order to ensure good ergonomics and high assembly quality. Worn bits wobble during tightening. This movement causes unnecessary vibrations which are harmful to users, reduce the service life of the tightening tool and have an adverse effect on the quality of the joint. If you take action early, you can kill three birds with one stone.” The product manager says that replacement is inexpensive and brings considerable benefits. He recommends the use of guided sockets and extensions. “The tailor-made adaptation of these parts ensures a better fit. Vibrations are minimized and less energy is wasted in the transmission of forces to the joint. Wear is reduced and the repeatability of tightening is improved,” says Kierakowicz, summing up the benefits.

Practical Seminar on Low Reaction Tightening

Customers and people interested can find out all they need to know about low reaction assembly at our LRT Academy (low reaction tools). This workshop consists of three modules covering the basic principles of tightening technology, ergonomics and technical solutions both in theory and during practical work in groups. “We can provide users with even more confidence in this key area and offer this seminar free of charge,” says Michael Kierakowicz.