Robotics Case Studies
KUKA Long Range Robot Outperforms Layering Palletizer
by Yarek Niedbala
KUKA Robotics Corporation
A robot is required to palletize soft packages onto a pallet. The essential characteristics of this robot, which is used at a beverage manufacturing plant, is an emphasis on flexibility and availability The robot works on two sides, alternately stacking two sizes of soft packages on Europallets. The six-axis robot, which has a large operating range, is also equipped with a newly-developed, independently moveable fork-shaped gripper. The method of operation of this end-effector makes it possible to vary the stacking pattern, which greatly enhances the stability of the palletized load.
The company Hauser GmbH, which produces wine-based beverages, wine and iced tea, was founded as a family business in Fischach, near Augsburg, Germany, in 1954. With 70 employees, the company supplies its products mostly to discount chains operating primarily in Germany, but also in other European Union countries. The beverage producer’s success can be seen from its number of employees and its sales volume; both of these have been on an upward trend for a long time now. At present this user, working for the most part in three shifts, fills over 200,000 Tetrapaks per day; the second type of container used is bottles.
Previously, the user had employed a layering palletizer to stack the soft packages on the carriers. Making new investments had become necessary because of rising throughput, and the management decided in favor of a robot. “A robot is more flexible when changing to a new product”, explains Walter Lau, Technical Manager at the Hauser plant. “In such situations a layering palletizer would have to be reconfigured, which is time-consuming. With a robot, on the other hand, all that one has to do most of the time is select the appropriate software program, and, if necessary, use a different gripper. In addition, setting up a robot at a different location is faster.”
Today, this user works with a KR 160 PA Long Range robot from KUKA Roboter GmbH, based in Augsburg, Germany. As its name indicates, this robot is remarkable for its exceptionally long reach. Used as a palletizer, the robot handles cardboard trays filled with soft packages. This involves either twelve 1-liter packages with wine, or eight 1.5-liter packages with iced tea. At full capacity, the robot palletizes 1,850 trays per hour; approximately 40 million soft packages pass through the cell per year.
The complete robotic cell, which besides the robot and its controller also includes the conveyors to and from the cell and the safety devices, was designed and installed by the KUKA systems partner RST Roboter-System-Technik GmbH from Barbing near Regensburg.
The relevant criteria in selecting the robot were the geographic proximity of the manufacturer and the price/performance ratio. Ultimately the crucial factor, says Hauser, who also looked at alternative systems, was the low maintenance requirement associated with the robot. A fact contributing to significantly shorter downtimes is that the robot – in contrast to those from other suppliers – returns to the programmed path where emergency stop situation occurred, which makes restarting easier.
Two conveyors bring the trays, separately for 1-liter and 1.5-liter packages, from the production area to the robotic cell. First, an external fixture turns the carriers to a position where they can be gripped properly. The robot, which stands between the two conveyors, stacks the trays in a pattern consisting of two rows of six trays crosswise, and one row of four trays lengthwise. This palletizing pattern is offset from layer to layer, thus creating a stable structure.
The KR 160 PA can create stability by means of varying palletizing patterns with trays of 1-liter containers. The robot uses the same fork-shaped gripper to pick up six trays lengthwise; it rotates some of them in the gripper to the crosswise direction, this way creating the desired layer pattern. For this purpose the end-effector is divided into three sections, each of which can be used by the robot to shift two trays. Another important factor for the stability of the loaded pallet is the high repeatability of the layer pattern that the Long Range robot achieves.
The height of the load units is determined by the user individually for each customer. Since the KR 160 PA’s reach of 3.8 m in every direction greatly exceeds the 2.5 m required for this application, even higher stacks would be possible. Attention has also been paid to safety; should the gripper encounter an obstacle, the system is automatically switched off.
The robot is custom-set to move loads at 90 % of its maximum speed, and to move the empty gripper at 100 % speed. Faster handling of products is not desired, since the cycle time of the robotic cell is within that of the filling cycle, and faster sequences would compromise the integrity of the packaging.
“We expect that the entire robotic cell will have paid for itself in about three years. The figures for a layering palletizer would have been similar, but one must also consider the markedly higher maintenance and operating costs”, says Walter Lau in summary. “Furthermore, conventional equipment would have required a significantly larger area for pre-accumulating the trays.”
The cost-effectiveness of this new concept can also be seen from the fact that the Long Range robot can handle about double the workload compared with the layering palletizer previously used. Thanks to this advantage, and its strong effect on production efficiency, today Hauser is able to operate in parallel four filling machines.
Author: Jürgen Warmbold, freelance technical journalist, 27327 Martfeld