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Motion Control Resources

Nimak uses servo drive system to revolutionize the design of welding guns

by WITTENSTEIN with Nimak
WITTENSTEIN

The compact design of our innovative motor/gearbox unit – in combination with high torque density, rigidity and dynamics – inspired NIMAK to design a completely new welding gun system: thanks to the galaxy®GUN, the productivity of welding processes is significantly improved. And that’s not all: force generation is rapid and dynamic, so that it is now also possible to weld new and different materials.

Galaxie®: Enabler for next-generation concepts

Again and again, Galaxie® causes existing design strategies in high performance engineering to be overturned. This new gearbox class has several decisive features: dynamic teeth instead of a rigid gear ring, tangential and hydrodynamic tooth contact over the full surface when loaded rather than pitch-point linear contact and a new type of bearing with a segmented outer race ring. All of these innovations add up to a novel design principle, with the result that Galaxie® is clearly superior to established planetary, cycloidal, eccentric and standard strain wave gearboxes in all key technical disciplines compared to the market standard.

NIMAK chose our Galaxie® D in size 135 on account of its compact design and high power density. The company’s engineers were thus able to mount the complete drive unit directly at the gun’s pivot point and dispense with the basic gun body that is normally a must. The gun has an up to 50 percent smaller interruption contour on the robot as a result.

»Thanks to Galaxie®, we were able to break with all previous design conventions and completely reinvent the welding gun. «

NIMAK – SPECIALIST FOR THE PERFECT CONNECTION

NIMAK GmbH, which has its headquarters in Wissen east of Bonn, has globally unique expertise in two different fields: resistance welding technologies for steel and aluminum as well as joining know-how in the form of gluing and dosing systems for non-weldable multi-material mixes. The company enjoys a reputation among customers and users as an innovation leader in both of these areas. NIMAK additionally has the capability to build complete robot systems using technologies developed in-house, integrating the welding and gluing processes in one. Robot welding guns were invented by NIMAK, who also helped this technology gain widespread acceptance. Today, NIMAK is the largest German manufacturer in this sector and a top international supplier.

»Never before has a welding gun had such a compact design with so few components. «

GALAXY®GUN: WELDING GUN REINVENTED

Conventional welding guns are configured from a modular system comprised of various basic bodies, gun arm designs, servo drives and medium frequency transformers. A totally different concept was invented for the new galaxy®GUN. The basic body, Galaxie® Drive System and gun arms are now all combined in a much more compact and approximately 20 percent lighter module. The decisive innovation here is as follows: the torque-dense, highly dynamic and extremely torsionally stiff drive system is integrated into such a small space that it could be mounted directly at the gun’s pivot point. As a result of this, the rotary motion of the drive is now converted into the gun arm movement with absolutely no slip. What’s more, the electrode arms can open much wider than is possible with conventional robot welding guns and thus steer clear of interruption contours in the vicinity.

GALAXY®GUN MAKES EVERYTHING EASIER

Thanks to the galaxy®GUN, NIMAK’s modular system for welding guns has been greatly simplified and the assembly time is significantly shorter.

The concept also opens up new options for realizing customer projects. NIMAK is now in a position to configure and provide guns sooner, which means there is more time for on-site simulation and commissioning. The gun geometry no longer needs to be adjusted and measured. Servicing of the galaxy®GUN and stocks of spare parts are likewise far more efficient and economical.

VERY SHORT CYCLE TIMES AND PERFECT WELDING RESULTS

The new design approach with Galaxie® D as the central component has numerous benefits:

The drive system allows more rapid opening and closing of the gun arms; the force generation time is shorter and the repeat accuracy of the electrode force extremely high. Since the guns can now be designed with less mass and the center of gravity is close to the robot’s flange connection, the robot can move the guns faster. The galaxy®GUN’s low weight likewise enables more dynamic robot motions. Galaxie® D’s high dynamics and torsional rigidity not only permit ultra-precise process control based on active force profiles but also lie behind the even more dynamic follow-up characteristics of the electrodes. Finally, shorter welding times are possible – the spot welding process for aluminum is now completed in as little as 100 milliseconds.

»The Galaxie® is unquestionably the most power-dense and precise drive system in today’s global market «

FIRST PROTOTYPE AFTER ONLY A FEW WEEKS

We originally showed NIMAK our Galaxie® early in 2017. The presentation and the sample of the Galaxie® gearbox kinematics evidently inspired the company’s engineers. The high torque density in relation to the volume and dead weight of the drive system were the starting point for something radically new. The first prototype of the galaxy®GUN was ready and integrated in an experimental robot only weeks after the specification was agreed. The results of the field tests spoke for themselves – and NIMAK was able to unveil the new robot welding gun at “Schweißen und Schneiden”, the international trade fair for welding and cutting, in September 2017.

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