High-rack and block storage
Storage of laminated plywood panels at Pollmeier
MINDA develops a buffer and high-rack storage for laminated plywood panels. Both storages were installed at Pollmeier Massivholz in Creuzburg this year. Apart from the steel construction the scope of delivery included the complete mechanizing and control.
The customer requested to store as many laminated plywood panels (6 m up to 18.1 m long and 100 mm up to 1,900 mm wide) as possible in a 20 m high building with individual access and to transport them to the following further conversion in an order-related way. Hereby the average storage time should be shorter than one minute. In case of errors or interruptions of the further conversion, the continuous production plant for laminated panels should be discharged without any loss of performance. This storage must be operated at an internal temperature of 60° C to 70° c in order to condition the panels for further conversion.
MINDA built a very slim and light steel construction consisting of closed frames. These frames were arranged one behind the other in a fixed pattern and with the screwed ceilling and wall panels they form the outer shell of the building. Cantilevers are fixed to these frames from inside in a very tight grid. The panels are deposited on these cantilevers on 120 places. As these frames were prepared to a large extent at MINDA in Minden, the high-rack storage could be installed at site within a few days. Now the building offers enough space for two rack feeders, the first was already installed.
The storage is directly connected with the production plant for laminated plywood panels via a roller conveyor. Three more roller conveyors in different levels help to feed the conversion as well as to return cut offcut panels.
Two lifting units with counterbalance face each other in the storage and are connected with a 18.5 m long traverse in light-weight construction. A master-slave control couples both lifting units within a millimeter. The system is balanced to half load capacity by means of counterbalances and thus requires a considerably lower installed lifting capacity. As a result, it only consumes low lifting energy at a lifting speed of 60 m/min. Special lifting belts made of steel rope are used as lifting elements. This lifting system is a clean and smooth solution which is totally free from wear and maintenance. On the traverse there are eight telescopic forks with two-sided stroke of 2.00 m. They pick up the panels from the feeding roller conveyor and store them at left or right hand side into the rack into a free compartment.
It is possible to store either a 1.90 m wide panel or several small offcut strips one beside the other in one compartment. These offcut strips can also be stored individually. For this system safety is of top priority. Errors with 1.5 t heavy panels should not appear in 20 m height and should be easy to solve. Therefore, special sensors monitor the storage of each individual panel and measure the free storage place in front of the panel in case of cut offcuts as well as the correct position of each panel in the storage.
The block storage is used to buffer large volumes of semi-finished and finished products.Panels of one dimension and length are stored one upon the other in 4 m height above the floor. This storage space is extended to a length of 100 m and is covered by a special crane with lifting unit and vacuum suction devices delivered by MINDA. As the pick-up position of the crane is at the front side of the hall, the traction drive had to be designed for 180 m/min and high braking and accelerating forces had to be realized. Here the drive system is specially challenged. Therefore, vulcollan wheels with a diameter of 800 mm and two asynchronous servodrives with a drive capacity of 18.5 kW were installed.The wheels feature a very quiet operation free from wear. The drives allow an exact regulation and positioning with high dynamics. The stroke of 4.7 m is realized by two scissor-type systems. A total of six suction pads with automatic control valves are fixed at these lifting units so that panels of 6 to 18.1 m can be raised in any length, even possible defects are tolerated under a suction plate. Two short panels up to a length of 8.5 m are positioned one behind the other in the 18.1 m long storage and can also be individually handled.
During the procedure the panels are secured by means of a mechanic protection device so that the up to 2.5 t heavy panel does not fall down when the vacuum fails. The crane is fully-automatically driven in a secured area. The superimposed master computer defines the storage orders which are reported by the crane after execution. In manual mode the operator can control all crane functions directly for every stack by means of a radio-controlled controller in order to carry out, fo example, manual redistributions or removal of individual panels without any order by the master computer. The communication of the crane with the control is ensured by a safe W-Lan connection in order to guarantee a safe operation even at large distances and high data volumes.