Tlakovci Podlesnik is a family-owned business with its headquarters in Maribor, Slovenia and more than 35 years’ experience in manufacturing concrete products. The company has developed into one of the biggest suppliers of concrete products on the Slovenian market and possesses several production halls as well as exhibition areas in Ljubljana and Graz. For 30 years now, Tlakovci Podlesnik has relied on state-of-the-art technologies from Zenith in order to maintain high standards in quality and maximum productivity.
For the seventh time, the company has decided on investing in manufacturing systems from Zenith Maschinenfabrik GmbH in Neunkirchen, Germany. Following on from several stationary and mobile multi-layer machines, Zenith equipped this Slovakian company with a single-pallet machine for the first time in 2001. This fully automated system solution possesses continuously integrated logistics from preparing the concrete right up to packages ready for shipment. Now, a still higher performance Zenith 860-4 single-pallet machine has been added to the fully automated circulation system in Maribor with the aim of offering an even greater range of products and maximising production capacity. On top of this came a new intermediate board storage track and a new transverse transport device. Besides transport on the wet side, the control unit for the finger car was also modified and the drying racks were expanded. Now, a second packaging line can be inserted parallel to the existing finishing and packaging line.
The technical properties of the fully automated Zenith 860-4 single-pallet machine are set up for high production output. Its equipment features enable it to manufacture an extensive portfolio of products including almost all elements for civil engineering and landscaping. Concrete products with heights of 50 to 500 mm can be manufactured.
One important factor in deciding for the Zenith 860-4 was that its dimensioning allowed it to be perfectly integrated into the existing infrastructure. The machine was able to be installed unproblematically on the existing foundation without further modification work. On top of this, the existing bucket conveyor system was able to be utilised, also without alterations, for the new machine.
This meant that the installation could be carried out relatively easily and inexpensively. The Zenith 860-4’s compact structure makes it generally very suitable for machine exchanges.
The stations: lowerator, elevator and travelling intermediate storage unit could also be kept. The mobile elevator on the wet side was completely re-equipped with new hydraulics and a side-shift device integrated into the wet side.
The well-proven Zenith compaction system with Ultra Dynamic servo vibration guarantees the highest product quality. Podlesnik chose a one-piece vibration table with frequency and amplitude control that facilitates maximum product diversity and attains a centrifugal force of up to 175 kN. Alternatively, the machine can be supplied with a three-piece vibration table with frequency-controlled vibration motors.
These innovative Zenith compaction systems ensure optimum compaction for concrete blocks within the shortest of cycle times and make a major contribution to the system’s maximum productivity. The system is set up for a cycle time of 12.5 seconds when manufacturing paving blocks with facing concrete.
The machine is equipped with two precisely guided, hydraulically driven feed drawers to guarantee constant block heights even with moulds that are difficult to fill. This means that moulds are continuously and uniformly filled. The state-of-the-art proportional control units also ensure maximum speed, repeat accuracy and availability for the “mould” and “tamper” movements. Another benefit is an automated mould changing system for extremely short set-up times. Other special equipment features are the two Colourmix devices for core and facing concrete and tamper head heating.
The machine is operated by means of a 22” touch panel. Zenith has especially dedicated itself to the task of creating an intuitive, self-explanatory man-machine interface. New visualisation based on the Siemens WinCC visualisation system has been developed to this end. The excellent user friendliness with the new visualisation system has been received very positively by machine operators. Employees can operate the machine independently even after only a short time of familiarisation.
The innovative hydraulic and electric control unit makes highly precise machine processes possible with great speed at the same time. The hydraulic system is composed of two energy-efficient regulating pumps with good power output, each with an accumulator. This design allows very great acceleration and velocity to be attained in conjunction with the regulating valves. It also warrants good production reliability since the machine can run with only one pump.
Easier handling and more rapid dismantling and reassembly are possible thanks to the valves’ horizontal arrangement. Movements are blocked by locking valves when the machine is idle. It means that a safe position is ensured even with loss of power.
The machine is supplied with clean oil complying with requirements thanks to a very efficient filter system. This again guarantees good longevity and availability with the valves. Provision has been made for water cooling to be installed with the hydraulic system.
A Siemens PLC with a Generation S7-1500 CPU and an engineering framework TIA portal (TIA = Totally Integrated Automation) are utilised as control unit. This technology has been employed in the entire product portfolio at Zenith since 2014. This cutting-edge control unit technology allows even the most demanding control tasks to be taken on. Separate external electronics are no longer needed. The operator receives optimal support even for checks and maintenance tasks. The piston positions in the regulating valves, for example, are monitored and displayed. The functioning of a valve can be checked in this way and evaluated for preventative maintenance.
The control unit is also prepared for future research and development assignments to be carried out in consultation with Podlesnik. All control units are connected by networks so that online service is fully assured both for both new and already existing control units.
The drying chamber was erected in 2001 in cooperation with Rotho. In order to cope with the greater amount of output with the new Zenith single-pallet machine, the drying chamber was enlarged by four rows and provides space for 6,300 boards with its 10 aisles (25 m long) and 30 levels.
The control unit for the finger car was brought up to state-of-the-art technology and now possesses – just like the Zenith 860-4 machine – a 1500 Generation Siemens control unit with a 22“ touch panel. The existing switching cabinets continue to be utilised with this modification to the control unit. Only the PLC has been replaced with its operating concept and frequency converter. This inexpensive modification basically provides a new control unit – with all its advantages – for the finger car group.
The fully automated elevating platform is equipped with a double deck. Products of differing heights can be inserted in order to achieve great product diversity. This means that every level can be filled with flat products and every second or third with high products.
An additional intermediate board storage rack was installed to cope with the interim storage of the remaining production boards when manufacturing high products. Seven chain tracks controlled by frequency converters offer stacking space for 840 production boards, which are automatically cleaned, turned and stacked. The production boards are then conducted to the machine again from one of the 28 positions of the intermediate storage rack via the newly installed transverse transport device.
The well coordinated cooperation between Zenith and Tlakovci Podlesnik enabled the modification work to run without a hitch. The next extensions to the system are already being planned. The Zenith team of engineers and technicians ensures trouble-free commissioning as well as assuring maintenance and the long-term supply of replacement parts.
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