Robotic Material Handling: Bottles

Reprinted with permission from Robotics World Magazine, December 2001

Pyraser Bier GmbH & Co KG, founded in 1870 in Pyras, Germany, brews eight types of beer to meet demand in Bavaria. The company, which employs 45 persons, also sells carbonated beverages, juices and other non-alcoholic beverages. Pyraser uses refillable bottles exclusively.

At present the brewing industry has hard times ahead; experts predict the demise of almost a third of Bavaria's 650 breweries. 'In an increasingly competitive market, we must produce high-quality products in a cost-effective manner, and open up smaller target groups through the use of modern container forms and sizes,' said owner Georg Bernreuther. 'A good example of an innovative container is the beer bottle with a screw cap we developed in 1993.'

In the end, a brewery can only survive if it is a high-tech enterprise. For Pyraser, cutting-edge technology begins with its own wastewater-treatment facility, the use of biogas from a nearby waste dump and, now, the use of robots. 'It is important to optimize technical processes,' Bernreuther said. 'For this reason we need a highly flexible packaging system.'

Today, Pyraser uses two KUKA KR 150 robots equipped with pneumatic grippers, each of which works one shift, three days a week. Compared to the conventional palletizing systems that were used before, the floor space required has been reduced by approximately 150 square meters, a decisive factor in favor of the robots. Costs for the cell were comparable to those for the conventional equipment.

The brewery can fill 24,000 bottles in an hour; since the robots can handle 30,000 bottles (1,500 crates) in the same time period, they are in a position to compensate for malfunctions in other areas. To be able to handle the bottles delicately despite this high throughput, short cycle times without high acceleration values are needed.

While one of the KR 150s is taking four crates with empty bottles from the roller conveyor, lifting out all 80 bottles simultaneously and placing them on a conveyor belt, the second robot is taking the same number of full bottles from a belt, placing them in four empty crates and then putting the crates back on the conveyor system. To complete one cycle, the robots require 9 seconds for filling and 9.6 seconds for emptying.

A robot with a load-bearing capacity of 150 kg is needed for this application, since four full crates with half-liter bottles weigh 80 kg, and the end-effector weighs an additional 70 kg. The KR 150's carrying capacity can be increased to 200 kg through the use of a heavy counterweight.

KUKA systems partner RST Roboter-System-Technik GmbH supplied the complete robotic cell, including the robot substructure, the centering unit for the crates, the safety devices and a pneumatic gripper developed especially for Pyraser. The empty bottles did present one problem in the design of the end-of-arm tooling: sometimes bottles are stuck in the crates upside-down, so that they cannot be gripped by the robot.

To prevent system malfunctions and time-consuming manual intervention, the KR 150 must be able to remove the crates from the pallet regardless. The robot, after two failed attempts to grip the bottles, moves at only 10 percent of its usual velocity while increasing the pressure of its wrist, enabling the robot to engage its gripper hooks in the crates and lift them off.

The robots' low maintenance requirements and their design are reasons Bernreuther refers to them as 'fun' machines, and said that he is looking for more ways to use them. For example, in the future the robots already installed are to be equipped with tool changers so they can also be used to handle barrels. This way the strength-sapping manual work of moving the full barrels, which weigh 65 kg, can be avoided.