The Mohren Brewery August Huber in Dornbirn, Austria is the oldest private brewery in the Vorarlberg region. The company’s success story began with an inn named for the “Moor”, one of the three Magi who followed the star to Bethlehem. In May 1834 Franz Anton Huber bought the inn “Zum Mohren” and its associated brewery.
This family business was able to increase its production from 300 hectoliters in 1834 to more than 170,000 hectoliters per year today. Computerized filling and monitoring equipment ensures consistently high quality. In fact, including resale merchandise, which mostly consists of non-alcoholic beverages, the company’s total sales significantly exceed 200,000 hectoliters.
With over 100 employees, the Mohren Brewery has an annual turnover of about 300 million Austrian schillings. “Our core sales area is the Vorarlberg, but we also have a strong presence in the Tyrol, Vienna, and the Burgenland region”, explains Dipl.-Ing. Ralf Freitag, master brewer at the Mohren Brewery. “Most of our customers come from the restaurant and food retailing businesses. In addition, because we were the first brewery in Austria to use PET bottles, we were named as the exclusive supplier to the Vienna Love Parade, and we also deliver to many other music events.”
Advantages of the “palletizing expert”
The Mohren Brewery has been automating its processes for some time now. One example of this is their so-called “keg robot”, a KUKA KR 150 robot which since 1997 has been transferring empty kegs from a roller conveyor to a washing system. After the kegs have been cleaned and filled, the robot fits protective caps on them, marks them with a code, and then places the kegs on the outgoing roller conveyor.
In April 2001 two additional KUKA robots were put into operation in Dornbirn. These KR 180 PA palletizing robots replaced a layer palletizer which had already had a “career” of 26 years. Today the company’s entire beer production, with the exception of the 35 percent which is put in kegs, is handled by the new system.
The KR 180 PA, developed by KUKA Roboter GmbH of Augsburg, Germany, is a four-axis “palletizing expert” with a passive fifth axis. The KR 180 PA’s advantage over conventional robots primarily lies in its application-specific, FEM-optimized kinematic system. Its arm is made of carbon fiber composite material (CRP), which thanks to its smaller mass moment of inertia has truly remarkable acceleration rates. Despite its lightweight construction, the arm has high stiffness, allowing the KR 180 PA to move loads weighing up to 180 kg, including the gripper. In addition, the space inside the robotic cell can now be used even more efficiently – KUKA has reduced the KR 180 PA’s interference contours compared with the previous model.
Four-axis robot saves costs
Another advantage of the four-axis KR 180 PA is its lower manufacturing cost compared to a six-axis machine. Additional cost savings are achieved through the extensive use of standard components, and the ability to automate up to eight pallet stations using a single robot. Another benefit is reduced maintenance requirements, facilitated by a quick-change energy supply system and the greatly reduced number of components used.
“In selecting this handling equipment, we took into consideration the range of different products we anticipated for the future. For example, we could later use the flexibility of jointed-arm robots for palletizing trays. Moreover, given the amount of floorspace available we had no alternative but to use a system of comparable efficiency”, says Ralf Freitag. “We also decided on this robot type, the KR 180 PA, because of the distance and depth of its reach. Furthermore, the more economical four-axis robot meets the requirements of our application”.
Only KUKA jointed-arm robots were considered. Firstly because the Mohren Brewery is very satisfied with its keg robot, and secondly due to the smooth cooperation with KUKA systems partner RST Roboter-System-Technik GmbH from the town of Barbing near Regensburg.
RST supplied the complete cell; this included the robots and grippers, equipped with a collision safeguard, the incoming and outgoing pallet conveyor equipment, the systems for raising and lowering the full or empty crates, the sensor systems and safety facilities. The two robots, each of which can handle up to 36,000 bottles per hour, are mounted in a space-saving configuration on platforms above segregating conveyors for “good” and “bad” pallets.
Hook gripper for four crates
The crates of full bottles enter the robotic cell from the upper floor of the brewery on a chain conveyor equipped with stop hooks. As they arrive, they travel on a side-flexing slat-band chain up to the fixed stop of the pickup position. There the KR 180 PA uses its hook gripper to reach into two of the lifting handles at the sides of each crate, picking up four crates at a time and setting them down on a europallet. The robot stacks 0.33-liter bottles on the pallets in six layers, and 0.5-liter bottles in five layers. One layer contains eight of the 300 x 400 mm modular crates.
Once the pallet in question is completely loaded, it is moved on the roller conveyor to a corner-turning station, which also serves as a double pickup station for forklift trucks. These two stations function as buffer positions; two others are provided on the roller conveyor itself. This means that the forklifts, which are equipped with two forks to allow simultaneous handling of two pallets, can operate independently of the cycle of the robotic cell.
Gripper compensates for height variations
The layout of the left side of the cell, where the empty bottles are depalletized, is analogous to that of the right side. Here forklifts transfer the empties to the corner-turning station, from which the pallets move along the conveyor to the emptying equipment.
The robot always depalletizes four crates at a time using its clamping gripper. In order to hold the two center crates more securely, additional safety clamps have been installed. This enables the KR 180 PA to even lift full crates, which occasionally appear among the empties. If the clamping gripper closes too far because a crate is missing or damaged, the robot stops immediately. Furthermore, springs integrated into the gripper compensate for height differences caused by tolerances in the crates and pallets. If the deviation is too large, the robot is likewise stopped automatically, thus avoiding damage. In fact, the height of each pallet is always measured when it first enters the cell. If a pallet exceeds the specified dimension, an error message is generated and the system is switched off.
The robot sets the empties on a slat-band chain leading to the upper floor of the brewery, where they are filled. The empty pallet is moved on a traversing carriage to the pallet magazine or the loading KR 180 PA. Damaged pallets are placed on a separate roller conveyor under the magazine and offloaded from the cell at the command of a PLC functioning as a master.
The PLC communicates with the PC-based robot controller via a bus system, specifying which containers are to be palletized. The PLC also signals when crates and empty pallets are available. The entire system is designed to be user-friendly: as for the KR 180 PA, for example, the robot controller’s KUKA Control Panel with its familiar Windows interface plays a major role.
Attention to the smallest details
In designing the facility, KUKA systems partner RST took even the smallest details into account. All installations, even the cable ducts, were mounted above floor level, thus enabling easy cleaning of the cell. What is more, the two robots are safeguarded in such a way that cleaning personnel can enter the unloading area while the loading robot is still in operation.
In his initial summary regarding the conversion, Ralf Freitag notes the following benefits: “Because we have significantly less breakage, we achieve more consistent quality than before. Moreover, considerably higher availability means lower personnel costs. There is also the significantly lower noise level, which can be attributed to gentler crate set-down and quieter conveyor systems.”
Another highlight is the flexibility of the system; introducing modifications is no problem. For example, another roller conveyor could be added to accommodate a wide range of disposable containers. And with additional grippers and a tool changing station, the KUKA robots would be able to handle even more types of container.
Author: Jürgen Warmbold, freelance technical journalist, 27327 Martfeld, Germany