LUZI AG was founded in Zurich in 1926 as a trading company for imported perfume components, aromas and ethereal oils. The company soon also began to develop and manufacture its own products. LUZI AG started supplying to customers in other European countries in 1954, and in 1969 the company moved into a new building complex in Dietlikon near Zurich. Today the company, which is ISO 9001-certified, is confronted with rapidly changing and increasingly differentiated markets. The fragrance compositions are created for the specific customer. Purchasers come from all over the world, and include perfume manufacturers and anyone else who uses fragrances in their products. With 43 employees, LUZI’s annual production amounts to 400 to 450 tons.
Robot creates new job
While the company generally works in one shift, five days a week, the robotic cell is in operation seven days a week in three shifts. Before the cell, which is equipped with a KUKA KR 125 robot, began work in the middle of July 1999, loading and unloading of the dispensing system was still carried out manually. Even before that, however, the formula was selected using a PC, and mixing was carried out automatically. But in an environment of rising sales, manual handling eventually became less and less cost-effective; automation of this activity was thus absolutely essential. Because the KR 125 is in operation “around the clock”, and a certain proportion of manual work is required for each mixture, the cumulative scope of this work increased significantly. To cope with this greater workload, it even became necessary to hire an additional employee.
The robotic cell was supplied by the KUKA systems partner IMT Anlagen AG from Therwil, Switzerland, which first assembled and tested the cell at its own plant. IMT was contracted to supply, in addition to the robot itself and its controller, the conveyor system to and from the cell, various stations for the KR 125 to move to, and the safety devices. The main requirement was higher throughput for the dispensing system. “With support from the robot we have increased output in this area from a maximum of 32 mixtures per day previously to 70 - 80 mixtures today. To do this it is extremely important for the robot to move to all desired positions with high repeatability, and accurately pour the mixtures into different containers when necessary”, says Daniel Knecht, Director of Manufacturing at LUZI AG. “We were also interested in improving working conditions for our employees. The buckets, which weigh up to 50 kg, would no longer have to be lifted onto the roller conveyor or emptied by hand.”
LUZI mixes the fragrances in two sizes of container: those which can contain up to 20 kg, and those designed for up to 50 kg. Employees place the empty buckets on one of six roller conveyors which feed into the system. As soon as the dispensing system is ready, the KR 125 takes a bucket from one of the conveyors and holds it under a lid reading station. This station lifts off the lid after the programmable logic controller of the filling system has read the container number from a chip attached to the lid. Then the robot places the open bucket on the traversing carriage of the filling system.
The system is adjusted to the height of the larger container; an adapter thus has to be used with the smaller container. This adjustment is also carried out by the robot. As required, the robot takes an adapter element from one of the setdown stations installed in the cell, or returns the adapter there. Since the two container sizes also have different diameters (40 cm and 34 cm) an adjustment must also be made to the end-effector of the robot. IMT has installed a changing station for this purpose. In this station, the KR 125 places an insert for the smaller container in its gripper. This gripper has been developed especially for this application.
As soon as an empty bucket is present on the traversing carriage, the carriage positions it under a series of different valves belonging to the filling system. This continues until the automatic part of the dispensing is completed. The correct mixture of the 128 most frequently used materials available in the system is stored in the PLC, together with the container number. The computer uses scales built into the carriage to check the fill quantities, thus providing additional quality assurance. As soon as this process has been completed, the KR 125 picks up the bucket again and holds it once more under the lid reading station, where the lid is replaced. Each individual position of the robot is monitored via limit switches by the PC-based KR C1 KUKA robot controller, which also maintains communication with the PLC.
In the last step, the KR 125 places the container on one of the four roller conveyors leading away from the cell. This conveyor area is, like the one leading into the cell, arranged on two levels, one above the other. The upper levels are reserved for the small containers, and the lower one for the large containers. This makes manual removal of the containers from the roller conveyor much easier. At the end comes manual dispensing, which is essential, for example, when crystalline products, powders, or materials that have to be heated are to be added.
If the weight of the mixture exceeds 50 kg, an alternative process sequence comes into play. In this case, the robot, instead of placing the containers onto the roller conveyor, empties them into one of three tanks. The KR 125 repeats this process several times, depending on the total volume of the mixture. Tanks with a capacity of 200, 260 and 650 liters have been installed. Two of these are sunk into the floor; their contents are removed by letting them flow into the basement. When the third tank is full, it is transported out of the robotic cell on a manual pallet truck.
The KR 125 carries out its entire spectrum of tasks in an area covering only about 20 m2. This also includes the three tanks, whose diameters range from 55 cm to 96 cm, the robot controller, and the changing, lid opening/closing and adapter stations. Due to these extremely cramped conditions, the robot often guides the containers close to its own “body”. On the other hand, the robot has to have a reach of 2.5 m, including the gripper, in order to be able to place the buckets on the outer upper roller conveyor.
Only system of its kind in the world
“Since the operational utility of this robotic cell is very high, it should pay for itself within two years. This investment produced not only significantly higher productivity, but also much more consistent quality at a high level”, says Daniel Knecht. “Moreover, we now have a technological lead over our competition, since no other comparable system exists anywhere in the world.”
It was different before: manual handling proved to be too slow during peak demand periods, and employees had to be kept on hand for overtime. Today, the operator responsible for the system calls up the desired formulas on the PC before the second shift, and then goes home. Up to 52 mixtures per night can be ordered in this way; capacity is limited only by the number of containers the roller conveyor can handle.
Because the robot is in operation almost continuously, a high availability is required. With the KR 125, this is nearly 100%. To further ensure this high availability, LUZI’s decision-makers are considering also using in the future the remote servicing offered by KUKA Roboter GmbH.
Author: Jürgen Warmbold, freelance technical journalist, 27327 Martfeld, Germany