Panasonic, known in Europe primarily as an electronics manufacturer, is also an internationally renowned manufacturer of robots, especially welding robots – with more than 30 years of experience in this segment. For many years, the major Japanese corporation has been using precision gears from Nabtesco for these robots. Panasonic Robot and Welding Systems Europe in Neuss has now added a new product to its portfolio: welding robots with heavy-duty rotary/tilt tables. And once again the design engineers used gear heads from Nabtesco.
While the Panasonic standard positioners for welding systems can support payloads of up to one ton, the new heavy-duty versions require substantially higher payload capacities: depending on the version, they have to be able to handle a payload of two, three or five tons. In addition to the payload requirement, the use of Panasonic servo motors was a prerequisite for the construction of the new machines. One of the tasks faced by the responsible area manager, Sergio Maeda, therefore was to find the ideal compatible gear head. After thorough research and consultation with several suppliers, he finally decided on the gear heads of the Nabtesco RD-C series.
For one thing, RD-C gear heads drive the horizontal rotary axes of the welding tables, for millimetre-precise access to all welding points on this axis without having to change the clamping setup for the part. In addition, the horizontal rotation/tilting is also achieved by means of RD-C gear heads.
High standards of quality and precision
The following specifications were required:
- Gear head with a hollow shaft for cables.
- Bearings with high impact resistance for loading/unloading components.
- Direct adaptation of the Panasonic servo motor.
- Rigidity and precision for positioning accuracy of ±0.05 mm at r = 250 mm.
- Long service life.
- Straightforward design of the positioners.
- Optimal cost-effectiveness ratio.
Since Panasonic had also used Nabtesco gears for other positioners in the past and had only positive experience with respect to precision and durability, the decision to use gear heads from the drive specialist for the large positioners was logical. “The easy-going and uncomplicated cooperation with Nabtesco Sales quickly gave us the necessary information and the right product, namely the RD-C series gear heads,” explains Sergio Maeda. Besides the output precision, especially the reliability of the gear heads was decisive for the Panasonic engineers.
The modular design of the precision gears of the RD series allows their use in diverse applications. The ready-to-install and pre-lubricated gears have a calculated service life of 6,000 hours. An adapter for the most common servo motors is mounted on the motor flange. Thanks to the modular design, RD gears can be used not only in rotary positioners, but also in many other types of applications.
The very rigid construction and high precision makes the series ideal for demanding applications in which very fast positioning movements are achieved with high payloads. Two integrated angular contact ball bearings eliminate the need for the customer to provide additional bearings in many cases, which reduces the construction time as well as costs. The eccentrically connected drive allows more reduction ratios than with centred mounting, often eliminating the need for upstream planetary gears.
Inherently positive characteristics
RD-C gear heads are based on RV-C installation kits with a cycloid design. Like these kits, the gear heads feature a large through-bore with a main support bearing. This hollow shaft with a diameter of up to 150 mm can be used for shafts, lasers or – as in the case of Panasonic – cables and wires.
The high payload capacity, which can absorb impacts of up to five times the rated load torque, and a high torsional rigidity ensure that the gear meets the required standards for robustness. The high precision is guaranteed by the low backlash of less than one angular minute and the compact design is achieved with high reduction ratios (i up to 1/258) and high torques combined with a small gear volume. Also, no additional bearing is need on the mounting side. This reduces not only the construction and assembly time, but also the overall costs.
Panasonic has been using the gear heads since the end of 2011 in its heavy-duty positioners. “Just as with the Nabtesco gears in our robots, we are very satisfied with the reliability. Failure of the gears is not an issue,” says a very satisfied Peter Deutsch, Manager Technical Solutions Team.
More than four million Nabtesco planetary gears from in-house development and production are in use worldwide. The main area of application is in industrial robots, more than 60% of which use Nabtesco gears around the globe. Other diverse applications requiring high-precision and robust gears also rely on high-tech products from Nabtesco.
Automated welding
To access all welding points in a geometric structure, the clamping setup for the part often had to be changed in the past. This necessarily results in imprecisions and imperfect results. These errors then had to be found and eliminated in a time-consuming and expensive process, if at all possible. In many cases a repair or correction of the error was so cost-intensive that the part had to be scrapped. This is where component positioners with precision gears contribute immensely to reducing production times and costs. The part, now mounted so that it can be rotated and tilted, can be welded without changing the clamping setup. The result: precise weld seams of high quality with low production times.
