The success of rationalisation measures such as automation with industrial robots depends to a great degree on the periphery, namely the material flow and the gripper technology.

A very good example of this is the frequently encountered task of handling bales, containers or cardboard boxes and stacking them on pallets.

This can be done effectively only if there is a continuous supply of empty pallets and the pallets are removed as they become full, thus permitting fully automatic operation in several shifts. In order to achieve economic operation, it is also necessary to reduce or, if possible, do away with all non-productive times, such as the changing of the grippers to alternately handle pallets and cardboard boxes. Depending on the number of boxes per pallet and the number of shifts per day, this needs to be done frequently. One could, of course, use a so-called combi-gripper with gripping elements for pallets and boxes in a single system. However, such combi-grippers are in most cases fairly large and heavy, with consequent negative effects on the dynamic motion of the industrial robot. They may even make it necessary to use a larger and thus more expensive robot.

Messrs. Fresenius, a company which produces large quantities of products such as infusion solutions, was confronted with this problem in one of its factories. The infusion bags are placed in cardboard boxes, and a full box weighs 8 kg. The boxes are stacked in five layers of nine boxes each on Euro-pallets. The total output is up to 480 boxes per hour, or 10.6 pallets. This means that 11 pallets have to be provided per hour and these have to be moved to the loading station and positioned there.
The loaded pallets are removed from the loading station by a roller conveyor.

Flexible handling of cardboard boxes and pallets

This means that the industrial robot has plenty to do: it must not only move handle the 480 boxes, but also the 11 pallets. This, in turn, means that the gripper system must be changed, or at least reconfigured, 11 times per hour to handle the two different objects. If this takes only a few seconds per cycle. The total time in multi-shift operation is considerable, and this has a noticeable negative effect on the available pallet capacity.

However, Fresenius found an intelligent and very efficient solution to this problem, using the VacuGrip FX from Schmalz.
The robot-mounted large-area vacuum gripper consists of five FX modules. The outer four modules of the type FX-400/120 SV are used for handling three cardboard boxes with a total weight of 3 x 8 kg = 24 kg at a time, while the wooden Euro-pallet is handled by the inner gripper of the type FX-600/80 SW.

The two vacuum gripper systems differ in two respects: in the number of suction pads per module and in the their technology. In this case, the "SV" (check-valve) modules are better for handling the cardboard boxes, since any vacuum cells which are not in contact with the load are automatically switched off in order to maintain the vacuum in the other cells. In contrast, the "SW" (flow-resistance) technology is better for the handling of the rough and porous materials of the pallets and is also more resistant to blockage by wood chips and splinters.

Integrated intelligence controlled by the robot system

The intelligence of the universal large-area vacuum gripper system lies, on the one hand, in the design and configuration of the gripper on the basis of a standard modular system and, on the other hand, in the rapid switching between the two gripper systems. This is done, when initiated by the robot controller, while the robot is moving to the desired position, and thus without the loss of operating time.

In spite of its multifunctional design and the integrated vacuum generation with Schmalz multi-stage ejectors, the gripper system is very compact and light, compared with the above-mentioned combi-grippers and this means that the dynamics of the robot can be fully utilised, especially when moving with no load attached.

The people at Fresenius are very satisfied with this new type of robot handling of cardboard boxes and pallets. Including handling of the pallets, the industrial robot must execute about 200 cycles per hour in order to stack five layers of nine boxes (handled in groups of three) on pallets. Without the intelligent large-area vacuum gripper system VacuGrip FX from Schmalz, this could not be achieved in practical operations.

The responsible persons at Fresenius are so pleased with this robot-aided palleting with the aid of a universal vacuum gripper system that they are already planning the next such system. They want to relieve their personnel from the hard work of palleting the boxes manually and to profit from the increased productivity already displayed by the first system.