Shuttle vehicles and rails must be designed in a space-saving way, in order to reach a profitable height grid. The height of the rail is decisive for the reachable space utilisation, because the height arises in every storage level and the totes are stored with a greater, vertical distance as actual necessary. Thus, the space utilisation and the storage capacity are less than those of lifting beams or miniloads – also because of the need of vertical conveyors. On the other hand, the floor space required is almost the same. The rail usually features a high integration of functions. It combines the function of positioning, energy transmission, carrying and guidance of the shuttle as well as safety functions. The data transmission is normally done via WiFi or Bluetooth. The rack has to be realized in that way, that it is able to absorb the occurring force of the movement, even in the case of error. Consequently, the costs for this kind of rack are higher than those for systems, which don’t cause forces or only small forces into the rack.
A shuttle storage system consists of the following components:
– Shuttle vehicle with or without lifting functionality (MLS or OLS Shuttle)
– Vertical conveyor
– Railing system
– Transfer conveyors
Shuttle vehicles, which – regarding the design – aren’t bound to a specific aisle, can move themselves autonomous and therefore take functions in different levels or aisles of the rack. Therefore appropriate transfer devices are necessary. Shuttle vehicles can also be the replacement for automated conveyor systems, in order to bridge transport routes outside of the rack. Accordingly, the design of the shuttles must be appropriate for leaving the rack and moving on the industrial floor or on a rail system.
Shuttle storage systems are used to store or to buffer totes, cardboard boxes and shelf boards. Static line racks are referred as shuttle storage system, in which autonomous shuttle vehicles operate. Every single shuttle vehicle operates in one or in several rack levels, but not in all. Shuttles, which operate in several rack levels, feature a lifting function. Vertical conveyors are used to connect the rack levels. Those can either relocate the shuttle vehicles in another rack level or convey the load to the level of the pre-storage area. Shuttle storages are used preferably for highly dynamic applications and are assigned to the automated small-parts warehouses. Thus, they represent an alternative to the conventional storage system with lifting beams – or miniloads. Advantages arise with the possibility to scale the performance of the system by varying the number of shuttles. Hence, it can be reacting to peak demands and changeable capacity utilisations. The loading is done by load handling devices (LHD), as they are known from the miniloads. However, the LHD are optimised in reference to the application of shuttle systems. Therefore, the flexibility concerning different goods is given. Depending on the LHD different rack types must be used.
For many years, the lightweight construction for storage and retrieval cranes is driven by the requirements of performance and energy efficiency. There is a trade-off between operations and design in an automatic small parts store. A modern storage and retrieval crane has to provide a better performance without deteriorating the cost advantage and the storage capacity. An increase in the performance requires higher driving dynamics of the storage and retrieval crane, which requires a larger volume and a stiffer supporting structure to give a reduced calming time. This however leads to a deterioration of the approach dimensions and a reduced storage capacity. With the same volume of the supporting structure, the stability without changing the approach dimension can be implemented by an antipedalgear. This however leads to higher acquisition costs and reduced availability caused by an additional technical expense. Similarly the stiffness can be increased due to the lightweight construction with new materials, like Carbon Fibre Reinforced Plastic (CFRP). So the energy consumption as well as the stress of susceptible components will be reduced, what leads to a reduction of the operating costs and the availability. The acquisition costs will be significantly higher using CFRP. The evolution of familiar concepts , which rely on the use of thin-walled, edged or rolled metal structures, are reaching their limits with an increase of dynamic. This shows, for example when there are problems with the fatigue strength and results in cracks in the metal. This is why GEBHARDT decided to go a revolutionary way and rely on composite materials. The result is the GEBHARDT Cheetah.
Up to now the implementation of a consistently lightweight construction with composite materials failed because of the high material- and manufacturing costs. That’s why the implementation of the Cheetah-mast is made of standard profiles of composite materials. The critical buckling of the large volume mast can be prevented with the use of profiles in the thrust range of the mast. The storage and retrieval crane is made of different materials, mainly steel, aluminum and composite materials. This material mix breaks down the previous problems with composite material concepts in storage technology. Because the adhesive bonding has proved to be a good joining technology for different materials, a suitable surface pretreatment and adhesive technique was developed. Equally the adhered materials were checked regarding their aging, to guarantee a permanent bond. Adhesive Bonding is especially advantageous in comparison to welding, because there is nearly no thermal deformation which has to be corrected. Also the adhesive is using the complete contact surface of the joining members – e.g. in comparison to spot-welding. Furthermore the adhesive gives a higher damping to the overall structure, so the storage and retrieval crane gets an improved calming time after slowing down. Besides the development of the new product, Gebhardt also had to implement new technologies for the manufacturing process. Up to now the multi material mix and especially the use of composite materials were used rarely in intralogistics. To check the operational stability and the operational safety of the new storage and retrieval crane, the mast was tested on a servo-hydraulic vibration test rig. It proved it’s stability even after a few millions of load change and showed no damage at all. Testing also included tens of thousands of collisions with the buffer and emergency stops. That’s how the test stand trials and aging test reflect the whole life cycle of the Cheetah.