The implementation of customized high-efficiency cutting lines allows a renowned Italian company to conquer the most demanding global markets.
The high-efficiency sheet metal slitting line, recently installed by a renowned English Service Centre, constitutes a further link of the by now long chain of implementations that CAMU has interwoven worldwide and demonstrates that today higher and higher specialization is requested to deal with the market globalization. The line in question operates in the field of medium-small thicknesses, from 0.3 to 4 mm of stainless steel, galvanized sheet iron, hot rolled coils, with production speed of 240 m/min. The slitter line is composed by 25 t uncoiler/recoiler, infeed unit, the driving unit, the circular-blade shear, the recoiling group, the compacting scrap winder. The reference points for the design and the implementation of the line were the small thicknesses and the high production speed; the target of obtaining the best productivity, flexibility, efficiency and precision has been reached also thanks to the high automation degree that reduces failures and machine downtimes and allows the operator to manage routine activities, maintenance and repair interventions in full autonomy and safety, Let’s see how.
The first group of machines is composed by coiler, lift truck, guides for the automatic centring of the uncoiler, coil-pressing device and telescopic table and has the task of carrying the coil to the infeed of the driving group. The lift truck has been designed with long travel: 7,200mm. To avoid whatever bending incompatible with the high feed-speed line, a third support point has been introduced on the load coil. Sheet metal centring photocells assure the compensation of possible unbalances. The motorized coil-pressing device, integral with the structure of the uncoiler, has the function of automating together with the telescopic table, the operations of opening and infeed of the coil into the driving group with superimposed rolls called “pinch rolls”. This first group of machines is followed by the facing shears to trim the coil end and to allow the management of productions in continuous or of partial coils, as needed. It is a guillotine shears with hydraulic vertical movement with increased distance among the blades to allow the free sliding of the sheet during infeed operations. After the sliding table and the collecting box, are positioned the coil guide system and, successively, the shears with circular blades, the core of the plant, with related carousel for the automatic loading/unloading of blades.
The heart of the line: the shears
The shears, structurally optimized with the FEM analysis, is composed by a precision-machined electrowelded steel bed housing the fixed shoulder and the mobile shoulder with shafts mounted on precision bearings. The mobile shoulder shaft is super-precision ground to assure perfect parallelism. Bearings are ground and hardened on the surface for a value of 62 HRC. The displacement of the mobile shoulder is performed through hydraulic cylinder. The interpenetration of 350 mm blades is carried out through precision cam operated by eccentric bushes that grant notable cutting precision both for the machining stiffness and geometry. The interpenetration motion is hydraulically powered and visualized.
Spectacular blade change
To see the automation of the blade group change of the shears by CAMU is always a moment of great interest, as the various motions are very smooth and at the same time effective. During the unloading phase the spindles of the circular shears move away axially and position at the same height as the spindles of the carousel with 4 arms positioned in front. The front shoulder of the shears opens “like a book” in automatic and the pack under previous machining is unloaded on these spindles. Now the carousel is ready to perform the blade change. It gets in position with the new blade equipment to be introduced into the shears, a plate descends and makes the blade kit slide inside the shears. The lock nuts are supported by the fixed shoulder and, once positioned, are screwed by the operator who provides for pumping the grease. Without ever touching the blades! The blade change time is less than 4 minutes. After the circular shears is installed the device for conveying the scraps into the pit, scraps that will be afterwards wound by the scrap winder, with slitter at standstill. After the loop, in the second ascent ramp, we find two coil-sorters that have the function of spacing and positioning them to introduce them correctly to the winding on the recoiler spindle. Made of monolithic steel structural works with coil-sorting arm, the coiler is equipped with lift truck, with arms for the lateral containment and the lifting of coils carried outside for the unloading on the 4-arm carousel.
Automation and control and supervision system
The automatic line is controlled through 3 panels: the main one and two positioned at the beginning and at the end, to assure an easy control of each line section. The installed PLC is one of the most advanced available on the market, Siemens S7 300. The automation is conceived according to a multi-level hierarchical architecture so that each single automation system performs a specific function and communicates its action to the higher hierarchical level by serial way. This assures high speed in information exchange, great execution rapidity of functions themselves, high reliability and precision: all that results in notable productivity increase This philosophy involves also maintenance procedures, which are therefore much facilitated. Finally, we end our thorough analysis reminding that the whole line is provided with powerful but user-friendly supervision system: it allows a fast and easy control of each machining phase with clear visualization of the various operation and error signs of the different automation components.