During the autumn of 1998 Brunnhuber delivered an automatic crane to Pfleiderer Industrie AG as the centre piece of its new, fully-automated warehouse in Gutersloh, Germany. Pfleiderer’s warehouse system buffers, stores and retrieves unfinished chipboard. Every hour, eight chipboard packs arrive by lorry or materials handling truck and the same number must be removed from storage as this happens. In addition, four medium density fibreboard (MDF) packs are also placed and removed from storage. Squared timbers are used as spacers between individual packs. When automatically laying these timbers, they are unpacked from boxes as required so that the system had to be designed for 12 double packs.
Board packs are 2.1m wide, 5.31m long and can be up to 1.8m high. The warehouse is 35m wide, 118m long and 17m high. Packs are stored parallel to the length of the warehouse. Given stacks up to 12m high, a storage capacity of approximately 30,000m3 is achieved with 19 stacks along and 13 across the warehouse.
Design
The high performance requirements necessitated the use of a computer-controlled double-girder gantry crane with hoist trolley and a safe working load of 12.5t for the chipboard gripper.
Thorough consideration was given to continuous operation in 21 eight-hour shifts per week in view of the DIN 15018 grading in hoisting gear class H4 and load group B6. At nominal load sag is less than 1/3000 of the span. Gantry cranes are of air-tight welded box-girder construction. Laterally adjustable trolley rails are clamped on the girders in shock mounts which help to reduce noise during operation. All rail joints are welded along their whole cross-section.
All driving units are rated in group 5m in compliance with DIN 15020 or M8 in compliance with FEM. Both crane and trolley wheels are strictly dimensioned to DIN 15070. Trolley wheels from high-grade hardened and tempered steels to DIN 15090 are cage-mounted, to guarantee long service life and low maintenance.
The requirements for positional accuracy along all three axes leads to the use of frequency-controlled AC drives. Trolley transmissions are fitted directly to the drive shafts. To achieve speeds of 100m/min and 60m/min for crane and trolley respectively, and 30m/min for hoisting and lowering, the total output power of the installation is 200kW.
The performance available from the drives enables high values of acceleration and deceleration and hence high dynamic response to changes in direction.
Command and feedback position signalling for crane and trolley traverse movements is done by means of a contactless and wear-free laser measuring system. Smooth crane travel is ensured by installing this system on both sides of the crane track and by using separate control systems and dynamic compensation control. Feedback position signalling of the hoisting gear is performed by a positive multi-turn absolute encoder position system.
The chipboard grabber is suspended at four finely adjusted points to two special bottom blocks by means of lock pins. These are in turn securely rove in the open hoist using a special rope guide. The rope anchor points are also finely adjustable for height and are shock-mounted. This results in accurate positioning when hoisting and lowering.
A telescopic range of between 1.40m and 2.30m is possible. Eight limit switches are provided for the minimum and maximum grip widths. The four connecting blocks in the vertical gripper arms measure the actual board width.
A number of light control switches are fitted to the pedestal projections for height positioning. The gripper arm is driven electromechanically through multi-start screws.
Tilt monitoring and anti-rotation elements complete the safety mechanisms of the chipboard gripper.
Electrical control
Electrical control enables various modes of operation of the crane for in-process storage: in addition to fully automatic computer-control, there is also provision for semi-automatic and manual operation, which can be via radio control or from the fixed or travelling operator consoles.
All hardware is arranged centrally and moves with the crane. Air conditioning ensures operation under ambient temperatures of up to 45OC.
Normal operation is fully automatic. All placing and removal requests are communicated to the crane control system by
the warehouse management computer.
The Simatic S5-115U programmable logic controller (PLC) together with the Profibus bus system and distributed bus connectors ensures state of the art reliability and maintainability.
The chipboard warehouse has a fixed horizontal co-ordinate system at variable pack heights. The crane control system remembers the plan position and height of stored chipboard packs at all times.
A bi-directional optical barrier is used to transmit data between the crane sub-system, conveyor sub-system, timber placing stations and inspection stations.
The fixed operator console together with bus coupler and power supply for the bi-directional light barrier are integrated into the control sub-system for the fixed handling system near the placing and removal stations.
Both the travelling and fixed operator consoles have a multi-line alphanumeric display for displaying and classifying all status reports. Operator terminals can also be used for amending machine data such as start-up and braking curves, speeds, position co-ordinates, reference points and so forth.
For high availability a data modem for remote diagnosis with coupling to the PLC forms part of the system’s standard specification.
Collector wires are used for the crane power supply, emergency-stop signals and automatic-mode selection.
Power is supplied to the trolley and chipboard gripper by means of power catenaries. Particular attention was paid to the ground rules of the EMC Directive in the construction of the drives, and the selection and layout of the cables.
All the usual display, ancillary and safety devices associated with a
high standard of finish complete the fully automatic crane system: these include load memory, overload protection, full motor protection using wrapped PTC thermistors, hour meters as well as pre-selection controls, operating and emergency limit switches, generous lighting,
ample space for the movement of personnel and ease of maintenance.
Besides the design, the short commissioning period also contributes to maximum customer satisfaction.
The optimum technical solution, the high standard of quality and attractive price-performance has brought follow-on orders for Brunnhuber.