Flexible e-chains, cables and linear guides for grippers in order picking systems from BD Rowa

• What was needed: Reliable cable guide despite tight bend radius and complex movement patterns as well as the linear technology to guide the gripper system and the downpipes
• Requirements: Cable solution for multidimensional movements with bend radii of over 180°, linear technology for the gripper as well as for the guide of the downpipes
• Industry: Vending machinery
• Success for the customer: Customised solution for cables and cable guide, tests in the igus laboratory, particularly bend-resistant cables without core breaks with minimal wear, very compact type

In 1996, the then newly founded Rowa Automatisierungssysteme GmbH presented the first fully automated storage and picking system for pharmacies. In the meantime, Rowa has installed more than 5,000 of these systems, and in Germany, with around 3,000 installed systems, Rowa has even secured a market share of around 70 per cent. From the pharmacist's point of view, automation saves a lot of space and even more time. It also creates the conditions for reducing stock levels and thus capital commitment.

The centrepiece of the systems is the gripper system. The latest generation of the patented HD multi-picking gripper can move up to eight packs - of the same type or different types - at the same time. In the narrow aisle of the storage system, two gripper systems can work in parallel and without collision, which doubles the picking performance and allows the grippers to perform very complex coordinated movements in order to store and retrieve the required goods as quickly as possible.

However, the high degree of freedom of movement also places high demands on the energy and signal supply as well as the cables. These must be able to keep up with the multidimensional movements without any problems, which means that the energy chains and cables are subject to significantly greater demands than in most other automation applications. For example, the cable guide must allow S-shaped movements with very tight bend radii and be able to stretch in the opposite direction. Despite the heavy loads, a long service life and the lowest possible noise emissions were important to the customer. A fast circulation system was also required for the rapid and error-free delivery of the medication to the blister unit, for which a completely lubrication-free linear and cam guide was sought.

Rowa now uses the igus product range for energy and signal supply systems as well as the cables.
Even though the chainflex cables were explicitly developed for very high loads and intensive movements, the systems presented a special requirement profile. The frequent bending beyond an angle of 180 degrees and the simultaneous use of a very small radius put a lot of strain on the cables. In order to find the optimum solution, Rowa provided the igus team with two gripper systems. Endurance tests were carried out in the igus laboratory and the electrical specifications of the cables were tested - with the result that the decision was made in favour of partially different core cross sections. The focus was clearly on service life so that the systems can run maintenance-free.
Specifically, chainflex cables of type CF10 are used as energy and control cables and cables from the CF11 series as data cable. As a result of the tests, the conductors in all series are designed to be extremely resistant to bending, and the special stranding ensures permanent flexibility in several dimensions without core breaks and with minimal wear. In some applications where the cables have extremely small radii, a CF99 series control cable with an alloy conductor is used to enable even smaller radii.
In the case of the energy chain, which is subjected to the same stresses as the cables, the radius of the chain had to be customised depending on the installation space. The igus designers have done detailed work here to achieve maximum availability. The E2 energy chain series is used here in closed and open design on the gripper and the2500 series for the longitudinal travel of the complete gripper system along the shelves.

A drylin lead screw with plastic nut is also used for the precise linear movement of the gripper system into the shelves. And drylin W profile guides in special sizes, which can absorb higher tilting forces, are used as horizontal guides for the drop tubes to safely guide unpackaged medicines. The circulation system enables tight curve radii and low friction, which not only saves drive energy, but also minimises vibrations and keeps noise levels low.